Preface

It is estimated that by 2050 the world's population will exceed 10 billion people, which will lead to a deterioration in global food security. To avoid aggravating this problem, international organizations have recommended dietary changes to reduce animal calorie intake and increase consumption of sustainable, nutrient-rich, calorie-efficient products. In addition, growing awareness of the impact of food on human health and the state of the environment has justified the need to seek alternative sources of food. This has promoted a steady increase in demand for plant-based diets attributed to the growing vegan, vegetarian, and flexitarian population, increasing intolerance to animal proteins, and other factors such as ethical concerns, nutritional benefits of plant-based diets, and increased investments in the plant protein sector. To meet the growing demand for plant-based foods expected over the next decade, there is a need to incorporate new food plant sources that embrace climate-resilient production systems and optimize strategies to increase the yield of improved health-promoting compounds. Moreover, this development must be scientifically documented and efficiently and reliably transferred to the academic world and society, favoring the contribution of all sectors.

The chapters of this book are divided into three sections.

Section 1, "Nutritional Value and Health Benefits of Vegetables", includes three chapters. In Chapter 1 "The Beneficial Role of Nuts and Seeds in a Plant-Based Diet", Michael S. Donaldson aims to answer several questions on the nutritional value of nuts and seeds and their potential health benefits when these plant food sources are incorporated into a plant-based diet. Chapter 2, "African *Moringa stenopetala* Plant: An Emerging Source of Novel Ingredients for Plant-Based Foods", by Anteneh T. Tefera et al., summarizes recent evidence on the potential of this plant, considered a staple food and traditional medicine by the local East African people, as a novel source of ingredients for food, cosmetic, and nutraceutical industries. Similarly, in Chapter 3 "Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations", Ntsoaki Joyce Malebo shows the advantages of the consumption of African leafy vegetables as an alternative food source because of their high nutritional value and health properties. This chapter also summarizes the limitations associated with the intake of these plant sources due to their perishable character, low bioavailability of some bioactive compounds, and low acceptability by current consumers.

Section 2, "Bioactive Compounds from Vegetal Sources", includes Chapter 4, "Beneficial Effects of Extra Virgin Olive Oil Rich in Phenolic Compounds on Cardiovascular Health". In this chapter, Imen Ghorbel et al. clarify the beneficial effect of extra virgin olive oil on cardiovascular risk factors when included as part of the Mediterranean diet, and review the basic mechanisms by which the polyphenols present in this oil exert their activities.

Finally, Section 3, "Strategies for Nutritional Security", includes one chapter written by Kuntal Das et al. Chapter 5, "Biofortification of Rice, An Impactful Strategy for Nutritional Security: Current Perspectives and Future Prospect", discusses the advantages and challenges of rice biofortification as a strategy to improve human nutritional security. It also summarizes the dissemination among stakeholders and trends in acceptance by consumers.

In conclusion, this book is intended to assist and guide food scientists, engineers, and nutritionists working in the field of food science, as well as consumers who are aware of the need to adopt healthy and low environmental impact dietary patterns.

I would like to take this opportunity to thank all the authors who have participated in this book for their cooperation and the quality of their work. Editing this book has allowed me to interact with prestigious researchers from different countries such as the United States, Canada, China, India, South Africa, Ethiopia, and Tunisia.

> **Blanca Hernández-Ledesma** Institute of Food Science Research (CIAL, CSIC-UAM), Madrid, Spain

Section 1

Nutritional Value and Health

Benefits of Vegetables

Section 1

## Nutritional Value and Health Benefits of Vegetables

#### **Chapter 1**

### The Beneficial Role of Nuts and Seeds in a Plant-Based Diet

*Michael S. Donaldson*

#### **Abstract**

In the last several years research has been accumulating that demonstrates that nuts and seeds are beneficial for all people. While some plant-based diet programs have embraced the inclusion of nuts and seeds, other programs have eschewed nuts and seeds, remaining firmly committed to a starch-based dietary pattern. This chapter assembles the scientific evidence regarding the benefits of nuts and seeds into three issues: (1) The nutrient density of nuts and seeds compared to grains and legumes of the same caloric content, (2) The improvement of health outcomes and extra benefits when nuts and seeds are included in plant-based diets, (3) The safety of nuts and seeds when a person is dealing with cancer. As a result of examining these issues with the known scientific evidence it will become apparent that one to two ounces of nuts and seeds daily is a very beneficial part of a plant-based diet.

**Keywords:** nuts, seeds, cardiovascular disease, cancer, plant based diet

#### **1. Introduction**

The scientific evidence for the benefits of a plant-based diet is enumerated in the various chapters of this book. Much of the evidence comes from programs and clinical trials that avoided any added fats or fatty foods, even from plant sources. So a title containing "nuts" and "benefits" in the same sentence may seem like an oxymoron, a contradiction in terms at the least. The inclusion of fatty foods like nuts and seeds has been and continues to be a controversial topic within the plant-based research community. While newer publications from the last several years relate to benefits of nuts and seeds, the older plant-based diet literature largely found positive results without the inclusion of nuts or seeds. Dr. Dean Ornish and Dr. Caldwell Esselstyn established the benefits of a low-fat plant-based diet for reversing heart disease. Dr. Ornish was one of the first doctors to prove that a plant-based diet could reverse heart disease, using the best testing methods available to provide the evidence to sway beliefs [1]. Dr. Esselstyn also reversed heart disease using this very low-fat diet, having about a 99% success rate [2]. Both Dr. Ornish and Dr. Esselstyn were able to get their great clinical success purposefully avoiding nuts and seeds and any added fats in the diet. Their success has been continued by others as well [3].

On the other hand, the position paper of the American Dietetic Association states "A well-planned vegetarian diet containing vegetables, fruits, whole grains, legumes, nuts, and seeds can provide adequate nutrition." [4]. The use of enhanced intake of beans, greens, seeds, nuts, whole grains, and other colorful plant products is recommended for athletes by Fuhrman and Ferreri [5]. In examining protein intakes on plant-based diets Mariotti and Gardner warn, "An insufficient protein intake from vegetarian diets may occur if the diet does not include protein-rich foods such as legumes (the most traditional source) and nuts and seeds, or any protein analogs of animal foods" [6].

In view of the lingering scientific controversy of the inclusion of nuts and seeds into a healthy plant-based diet this chapter is written so that the information is clearly available in one place for people to understand how nuts and seeds can be beneficial. There are 3 main issues to be addressed in this article. They are:

1.The nutrient density of nuts and seeds compared to grains and legumes.


As a result of examining these issues, it will become apparent that 1 to 2 ounces of nuts and seeds on a daily basis is a very beneficial part of a healthy plant-based diet.

#### **2. Nutrient density of nuts versus grains and legumes**

The first issue is to examine the nutrient density of nuts and seeds compared to grains and legumes. To examine this issue, four common nuts and five common seeds were compared with five grains and six types of beans and lentils. A 200-calorie serving of each food was compared for nutrients, as this is just slightly more than a 1 ounce serving of nuts or seeds. Nutrient amounts were taken from USDA standard reference nutrient tables incorporated into the software program NutriBase (Version 11.71, Phoenix, AZ).

As shown in **Table 1**, equal caloric amounts of nuts, cooked grains and cooked beans vary in serving sizes, measured in grams. About 1 ounce of seeds or nuts yields 200 calories, while it takes about one cup of cooked grains or about ¾ cup of cooked beans to get the same amount of calories. The main difference is the amount of water that is not in nuts and seeds and the fact that fats pack more calories into a smaller space than carbohydrates and proteins.

#### **2.1 Macronutrient content in nuts versus grains and legumes**

Nuts and seeds and grains have about 6.5 grams of protein per 200-calorie serving, while cooked dry beans have about double this amount, at 13 grams of protein per 200-calorie serving. So for protein, beans are a better source of protein than nuts and seeds. Beans average 35% of the calories as protein, ranging from 26 percent (pink beans and chickpeas) to 40 percent (lentils). Nuts and seeds are about 14% protein, ranging from about 5 percent (pecans) to 20 percent (pumpkin seed kernels). Grains are similar to nuts in protein content ranging from 10 percent (brown rice) to 16 percent (quinoa).

*The Beneficial Role of Nuts and Seeds in a Plant-Based Diet DOI: http://dx.doi.org/10.5772/intechopen.110677*


*Food group with the highest amount of a nutrient shown in red. Rstd = roasted; Bld = boiled; Ckd = cooked; WW = whole wheat; wtr = prepared with water; cnd = canned; GN Bean = Great Northern Bean.*

#### **Table 1.**

*Proximate nutrient comparison of 200 calories servings of nuts, grains and dry beans.*

Carbohydrate content is again a big difference between nuts and seeds and grains/ beans. The carbohydrate content of nuts and seeds is very low, especially considering their fiber content. Nuts and seeds averaged about 3 grams of net carbohydrate per 200-calorie serving. Only pistachios were above 5 grams. Grains averaged about 34 grams of net carbs, while beans averaged 24 grams. About 72% of the calories in grains come from carbohydrates; 60% of calories in beans are from carbohydrates.

Fiber is another category where the beans are about double the amount in nuts and seeds and grains, with about 12 grams of fiber per serving of beans compared to about 4 grams for grains and 5 grams for nuts and seeds. Flax seeds and chia seeds are much higher in fiber than other seeds or nuts. The average fiber content without these two seeds is 3.1 grams per serving.

Nuts and seeds are rich in fat, with about 80 percent of the calories coming from fats. Pecans and walnuts are particularly high in fat, with 87 and 92 percent of their calories, respectively, coming from fat. Beans on average have about 4.5 percent of the calories as fat, except for chickpeas which are at about 24 percent. Grains are also naturally low in fat.

So, nuts and seeds are a modest source of protein, very low in carbohydrates and a rich source of fats. Grains are a modest source of protein, low in fat and have a large amount of starch in them. Dry beans and lentils are an excellent source of protein, very low in fat, and a very good source of fiber as well.

One of the benefits of nuts and seeds here is the lack of glycemic response from their consumption. A recent randomized trial compared glucose and insulin levels after consuming a 253-calorie serving of mixed nuts or unsalted pretzels after an overnight fast. In the pretzel group glucose and insulin levels 60 minutes after eating were elevated, while in the mixed nuts group neither glucose nor insulin levels were significantly different from baseline levels [7]. In addition to nuts, flax seeds and chia seeds are very rich in dietary fiber. When 15 volunteers took, in random order, a 50-gram glucose challenge by itself or along with 25 g chia seeds or 31.5 g flax seeds the blood glucose response during 2 hours was blunted significantly by 39 and 28% by chia seeds and flax seeds, respectively [8]. These seeds, especially chia seeds, were able to turn glucose into a slow-release carbohydrate with their high-viscosity fiber.

A comparison of the classes of fats in nuts and seeds is given in **Figure 1** for a 200-calorie serving of four kinds of nuts and five kinds of seeds. As seen in **Figure 1**, there is very little saturated fat in nuts and seeds. Almonds, pecans, and pistachio nuts are high in monounsaturated fatty acids (MUFAs) with over 50 percent of their fat as MUFA. Only walnuts, flax seeds, and chia seeds have significant amounts of omega 3 polyunsaturated fatty acids (PUFAs) as alpha linolenic acid (ALA), a short-chain omega 3 fatty acid. Walnuts, sunflower, sesame, and pumpkin seeds have a large amount of the omega 6 fatty acid linoleic acid (LA). In their unprocessed, raw form both LA and ALA are very valuable fats and are essential nutrients, not found in grains and legumes in appreciable amounts. This is another benefit of nuts and seeds. So, these raw nuts and seeds are a good source of LA and ALA, which can be damaged by roasting, especially for long times over the temperature of 300°F (150°C) [9]. Though only trace amounts are transformed into the long-chain omega 3 fatty acid DHA [10], there are many health benefits from ALA and EPA generated from ALA [11]. Overall, the fatty acid profiles of nuts and seeds are very favorable to cardiovascular health as MUFAs and especially PUFAs tend to lower cholesterol and the incidence of cardiovascular disease compared to saturated fats [12]. And whatever is protective of the heart is likely to be beneficial for the brain, bones, joints, and muscles of the body.

#### **2.2 Vitamin content**

A comparison of the vitamin content of 200-calorie servings of common nuts and seeds, grains and dry beans is given in **Table 2**. The Recommended Daily Intake (RDI) is given for each nutrient, as it is much easier to compare percentages rather than actual amounts. The nutrient amount for a particular food is in bold case for amounts greater than 20 percent of the RDI. As you can see, these foods are not a rich source of several of these vitamins, such as vitamin A, vitamin C, and vitamin K. These vitamins are found in higher amounts in fruits and vegetables. The vitamins which contents are high in nuts and seeds are mentioned in the text below.

#### **Figure 1.**

*A breakdown of the distribution of saturated, monounsaturated and polyunsaturated fats in nuts and seeds. SFA = saturated fat, MUFA = monounsaturated fat, Omega 3 = alpha linolenic acid, Omega 6 = linoleic acid.*



*Excellent sources of nutrients (*≥ *20% of RDI) are shown in bold case. Blank cells indicate missing data. Rstd = roasted; Bld = boiled; Ckd = cooked; WW = whole wheat; wtr = prepared with water; cnd = canned; GN Bean = Great Northern Bean.*

#### **Table 2.**

*Vitamin comparison of nuts, grains and dry beans, as a percent of the recommended dietary intake (RDI).*

A serving of sunflower seeds provides over 40 percent of the RDI for thiamin (vitamin B1). A 200-calorie serving of flax seeds provides over 50 percent of the RDI. Most seeds are generally an excellent source of thiamin, with pumpkin seeds being the exception. Grains on average provide 15 percent of the RDI. Beans are also an excellent source of vitamin B1, providing between 20 and 30 percent of the RDI for thiamin, similar to the average for seeds.

A serving of almonds provides over 30 percent of the RDI for riboflavin (vitamin B2). But most nuts and seeds are not this rich a source of riboflavin, averaging about 5 percent of the RDI. Grains and beans are not much better, with less than 10 percent of the RDI per serving.

Sunflowers are a notable source of niacin (vitamin B3), with 18 percent of the RDI per serving. But chia seeds are even better at 23 percent. Rice and whole wheat bread are good sources with 16–18 percent of the RDI of niacin per serving. Beans are not a rich source of niacin with only lentils providing more than 10 percent of the RDI.

Pistachio nuts and sunflower seeds are excellent sources of vitamin B6, with sesame and flax seeds also being good sources. Grains are good sources, except for oatmeal. Beans are also good sources, with chickpeas delivering over 60% of the RDI per serving.

Almonds and sunflower seeds are very rich sources of vitamin E. Most other nuts and seeds, grains and beans provide little vitamin E, but these two foods are two of the richest food sources of vitamin E. In a South Korean trial using 56 g/day of almonds

or a control cookie in a 4-week cross-over pattern, volunteers doubled their intake of vitamin E, which resulted in an 8.5% increase in plasma α-tocopherol levels while simultaneously reducing total cholesterol 5.5% and non-HDL cholesterol by 6.4% [13].

From this analysis of vitamins, we can deduce a few points. First, different foods have different strengths as sources of nutrients, so it is helpful to encourage people to eat a variety of plant foods to take advantage of different nutrient profiles to even out overall intake. Second, when averaging the percent of the RDI for each vitamin, sunflower seeds are, on average, the best source of micronutrients (19%) of all of these foods listed in **Table 3**. Almonds are also a good source of vitamins with an


#### **Table 3.**

*Mineral Comparison of Nuts, Grains and Dry Beans, as a Percent of the Recommended Dietary Intake (RDI). Excellent sources of nutrients (*≥ *20% of RDI) are shown in bold case.*

average of 11% RDI. Beans average is 12% RDI, with lentils coming in highest at 16%. This vitamin analysis shows that sunflower seeds, almonds, and lentils are great foods for at least weekly consumption, if not more frequently.

#### **2.3 Mineral content**

As can be seen from **Table 3**, nuts and seeds, whole grains and dry beans all provide a much higher amount of the essential minerals than of the vitamins. The RDI amount in milligrams or micrograms (for selenium) are given in the first row of the table.

Sesame seeds and chia seeds are both excellent sources of calcium, providing 26 and 20 percent of the RDI, respectively. Almonds and flax seeds are also decent sources, with about 95 mg of calcium per serving. Great Northern beans and navy beans are also decent sources of calcium, around 100 mg per serving, but the other beans are not so high. Calcium has long been a nutrient of concern for people following plant-based diets, so the inclusion of nuts and seeds rich in calcium will boost intakes of calcium compared to eating isocaloric amounts of grains.

Magnesium is a shortfall nutrient for the US population. About 50 percent of all American consume less than the Estimated Average Requirement (EAR) for magnesium [14]. Among the elderly it is worse, with 75% of men age 71+ and 63% of women age 71+ under the EAR for magnesium. Adolescents do not fare well, either, with 78 and 89 percent of males and females, respectively, 14–18 years of age consuming less than the EAR. Magnesium is very important for cardiovascular health, bone health, prevention of diabetes, cognitive function [15], and prevention of eclampsia during pregnancy [16].

Consuming more nuts and seeds can improve intake of magnesium. On average nuts and seeds are better sources of magnesium than grains or beans, though there is some variation. A 200-calorie serving of seeds averages 35% of the RDI for magnesium, making them a superfood for magnesium. Almonds are the only nut that is an excellent source (≥20% of RDI) of magnesium. Grains are good sources, with quinoa excelling at 25% of RDI for magnesium. Some beans are excellent sources of magnesium (black beans, Great Northern beans, pink beans) and the average for beans comes out to 18% of RDI for magnesium. Generally, grains and beans have only half of the amount of magnesium found in seeds, so substituting a serving of seeds for a serving of whole grains will improve a persons' magnesium status.

Though high intake of potassium is a strength of plant-based diets and contributes to normal blood pressure [17], strong bones [18], and cardiovascular and overall survival [19], nuts and seeds and grains are low sources of potassium, while beans are generally good sources. Potassium is found in abundance in fruit and vegetables, so this is where most of the requirements are met. Beans win this mineral by a two-fold margin.

Copper is easily obtained in a plant-based diet. It is easy to get half of the RDI for copper with a 200-calorie serving of nuts or seeds. Sesame seeds provide 1.4 mg of copper, almost 160% of the RDI. Beans are also an excellent source of copper, but not as good as nuts and seeds.

Plant-based diets need good sources of iron. Women of reproductive age following plant-based diets especially need iron to replace iron lost in their monthly reproductive cycle to prevent anemia. While some whole grains are good sources of iron, seeds are an even better source of iron, and sesame seeds are an excellent source. Nuts and rice are not rich in iron. Beans are a good source, with lentils and Great Northern

beans being excellent sources. Beans, on average, are a better source of iron than even the seeds.

Selenium is important as an antioxidant mineral, contributing to the synthesis of the intracellular antioxidant glutathione and selenoproteins. Good selenium status has been found to improve a body's defenses against viral diseases such as HIV and COVID [20]. Brazil nuts are well known for their selenium content, a listing of over 580 μg per 200 calories (30.5 grams, about 6 nuts). Other nuts are generally low in selenium along with beans, but most seeds are an excellent source of selenium. Pinto beans and Great Northern beans are good sources of selenium.

Zinc is an essential mineral with many roles in the body. Zinc plays a role in immune defense, showing effectiveness against respiratory viruses [21]. Higher dietary intake of zinc from non-red meat sources was associated with lower risk of progression of coronary artery calcification scores [22]. Nuts and seeds are generally good sources of zinc, with sesame seeds and pumpkin seeds being excellent sources. Wild rice and oatmeal, but not whole wheat, are also excellent sources of zinc from the grain category. Dry beans are good sources, with lentils being an excellent source of zinc.

In conclusion, when averaging the RDIs for all minerals, nuts have 15%, seeds have 28%, grains 19% and beans 20% of the RDIs. So, nuts are not as mineral dense as seeds, but seeds are a really good way of increasing essential mineral intake. Overall mineral intake is important, as indicated in a study of the Iowa Women's Health Study. Quintiles of mineral intake were used to create an overall mineral score, with positive scores for calcium, magnesium, manganese, zinc, selenium, potassium and iodine, and negative scores for iron, copper, phosphorus and sodium. Higher ranks of the mineral score were associated with lower risk of colorectal cancer in these 55- to 69-year-old women, up to 25% decreased risk comparing highest to lowest rank of mineral score [23]. So, increasing mineral intake by substituting a serving of grains out for a serving of seeds will likely reduce risk of disease.

#### **2.4 Summary of nutrient comparison**

To summarize this section nuts and seeds are the category of food that is the best way to get an extra 200 calories. When comparing just nuts and seeds versus grains one can see that nuts and seeds are more nutrient dense and deliver more nutrients per 200 calories. The average percentage of RDI for vitamins and minerals are 14.4 percent for nuts and seeds and 12.3 percent for grains (see **Table 4**). However, if we remove walnuts, pecans and pistachio nuts from the equation and just look at almonds


#### **Table 4.**

*Summary of comparison of nutrient density of food groups.*

and the seeds, the average RDI is now 17.6 percent. This is 43 percent more nutrition than what you get from grains, on average. So, seeds and almonds are more nutrient dense than grains.

When comparing nuts and seeds versus beans it can be seen that almonds and seeds have a slightly higher average RDI compared to the beans (17.6 versus 15.6 percent). So, even though they are lower in protein (about 7.5 versus 13 g of protein per serving) almonds and seeds are still overall more nutritionally dense than the average dry bean. For some nutrients beans, especially lentils, are actually more nutrient dense, so it would be wise to still be include beans in the diet as well, but not in the place of a serving of nuts and/or seeds.

So, it can be concluded that nuts, particularly almonds, and seeds are nutritionally more dense than grains, about 43 percent more. Seeds are also about 19 percent more nutritionally dense than dry beans in general. Should almonds and seeds replace grains in this 200-calorie serving? From a nutrient standpoint the answer is a clear yes.

#### **3. Health outcomes of eating nuts and seeds**

As mentioned in the introduction, Drs. Esselstyn and Ornish obtained excellent results in reversing heart disease without the inclusion of nuts and seeds. However, since the publication of their results there have been many investigations in the area of nuts and seeds. There have been short-term studies on the effects of various nuts on cholesterol and blood lipids. There have been short-term studies on satiety and weight loss and/or weight gain. There have been prospective cohort studies that have reported observations of groups of people over long periods of time. And there have been some randomized controlled clinical trials using nuts and seeds as well. Now we have more evidence about the benefits of nuts and seeds.

The issue to be examined here is whether health outcomes are better or worse when nuts and seeds are included in vegetarian or vegan diets.

This issue will be examined from four lines of evidence: (1) short-term studies on weight gain and obesity, (2) short-term studies on blood lipids, (3) health outcomes in population studies, and (4) vegetarian population studies in particular.

#### **3.1 Short-term body weight studies**

Since nuts are energy-dense foods, it is important to know if they caused weight gain, or if they were associated with obesity. In a review and meta-analysis of 33 controlled clinical trials, it was found there was no difference in body weight, body mass index (BMI) or waist circumference between the nut or control diet groups [24]. Population studies have also found that nut consumption did not affect body weight. People who regularly ate nuts actually tended to not gain weight or become obese over time [25, 26]. It appears that people compensate for eating nuts by eating less of other foods. Nuts' fat and protein content tend to make them a satisfying, filling food, whether eaten as snacks or with meals [27].

#### **3.2 Short-term blood lipid studies**

Since population studies have indicated that nuts reduced risk of cardiovascular disease, short-term studies have been conducted to attempt to deduce the mechanism for this health outcome. Many controlled clinical trials have examined different nuts

and blood lipid levels, but there are few reports including inflammatory markers and endothelial function. A review and meta-analysis of 61 blood lipid studies found that for a 1-ounce (28 gram) serving of nuts per day, there was a decrease in total cholesterol (4.7 mg/dL), low-density lipoprotein (LDL) cholesterol (4.8 mg/dL), ApoB lipoprotein (3.7 mg/dL) and triglycerides (2.2 mg/dL) [28]. The results were better for 2 ounces a day than for just 1 daily ounce. This significant, but small decrease in cholesterol levels is probably not the only reason that nuts are beneficial, but these results do point in the right direction. A recent review of 26 walnut controlled interventions found similar results, with no negative effects on body weight or blood pressure [29]. Almonds have been examined separately as well, with 27 almondcontrol datasets yielding very similar results [30]. So, the amount of nuts rather than the type of nut contributes to the lipid-lowering effect.

Studies have also examined the effect of nuts on blood pressure. No consistent significant results have been obtained [31]. Nor have there been significant reductions in markers of inflammation. Serum C-reactive protein has been measured in multiple studies with little change due to eating nuts [32].

However, there has been a consistent improvement in endothelial cell function, measured by flow-mediated dilation (FMD). Endothelial cells allow more blood flow through the release of nitric oxide. Flow-mediated dilation is a strong predictor of future cardiovascular disease [33]. A review of 10 trials found that nut consumption significantly improved FMD, but walnuts were the only nut that had a significant effect [34].

In summary, short-term studies have found significant effects on cholesterol levels, and walnuts for endothelial function, but no significant effects for blood pressure or inflammation. Nuts also contain phytosterols and other antioxidants that may be beneficial. Whatever the mechanism, long-term studies of populations of people have clearly demonstrated an advantage of eating nuts and seeds.

#### **3.3 Long-term studies of populations**

A recent review of reviews and meta-analyses on nuts and cardiovascular disease was published. There have been so many studies and meta-analyses of studies, which synthesize the information from individual studies into a coherent conclusive statement, that they could actually do an overview of all of the reviews and meta-analyses that have been done on population studies of eating nuts. There are 234 references to reviews, meta-analyses and large individual study reports in this article by Kim et al. [35]. Here is what these authors found about nuts and cardiometabolic disease. Consumption of nuts was associated with a 19–20 percent decrease in all-cause mortality. Coronary heart disease (CHD) incidence was reduced by 20–34 percent and CHD death was reduced by 27–30 percent. Cardiovascular disease (CVD) incidence (includes strokes as well as heart disease) was reduced by 19 percent and CVD death was reduced by 25 percent. Stroke incidence was reduced by 10–11 percent and stroke death was reduced by 18 percent.

In addition to this review, Aune et al. [36] have found a 15 percent reduction in total cancer death and a 39 percent decrease in diabetes deaths, and a 75 percent decrease in infectious disease deaths. For specific cancers, Wu et al. [37] reviewed 36 observational studies with a total of over 30,000 people. They found significant associations between eating nuts and a 15 percent overall reduction in cancer. Specific cancers with reductions were colorectal cancer (24% reduction), endometrial cancer (42% reduction), and pancreatic cancer (32% reduction). A recent meta-analysis by

Naghshi et al. [38], which included 43 articles on cancer risk and 9 articles on cancer mortality, found a 14% reduction in cancer risk associated with total nut intake, and a 13% reduction in overall cancer mortality from eating nuts, in close agreement with the work of Aune et al. [36]. A 5 g/d increase in nut intake was found to be associated with a 3, 6 and 25% lower risk of overall, pancreatic and colon cancer, respectively.

It is possible that the people eating nuts are just healthier overall because of other dietary choices and lifestyle habits. Even though population studies control for other dietary and lifestyle factors, there is a small question still. Direct evidence against the healthy nut eater hypothesis comes from a population study from Iran. In the 50,000 person Golestan Cohort nut eating was not associated with other healthy lifestyle habits. People who ate more nuts were also more likely to smoke, drink alcohol, be obese, less likely to exercise, but also were younger, of higher social economic status and had more education. In this cohort the nuts were still protective, leading to less coronary heart disease death and cancer death, especially among women. All-cause mortality was 29 percent less among people consuming three or more servings of nuts per week [39]. So, it appears that the benefits of nuts can be attributed to the nuts consumption and not to other lifestyle behaviors.

#### **3.4 Long-term studies of vegetarian populations**

The benefits of nuts have been seen among vegetarians and vegans who have healthy lifestyles as well. In a publication from the Adventist Health Study 2, there was a factor analysis looking at the sources of protein and risk of death [40]. For animal protein, there was a 61 percent increased risk of cardiovascular death, but for the nut protein factor there was a 40 percent decrease in risk of cardiovascular death. There were no significant associations with the factors for protein from grains, processed foods, or legumes, fruits, and vegetables. Among younger adults, aged 25–44 the meat protein factor risk was associated with 2-fold higher risk of cardiovascular death and the nut factor was associated with 3-fold lower risk. Nuts seemed to be protective and meat protein specifically seemed to increase risk of death. The protective effect of nuts was seen across different levels of plantbased dietary patterns in this population, suggesting that focusing on more specific plant protein-based diets may improve the ability of dietary recommendations to prevent CVD.

In the first Adventist Health Study this protective effect of nuts was first reported. When people who ate nuts at least 4 times per week were compared to those who ate nuts less than 1 time per week there was a 48 percent decrease in fatal CHD events and a 55 percent decrease in definite non-fatal heart attacks in the nut-eating group [41]. This protective effect was seen regardless of sex, age, smoking status, hypertensive status, vegetarian or nonvegetarian, exercise level, or whether or not people ate white bread. Nuts were protective despite all these other factors.

#### **3.5 Summary of health benefits of nuts and seeds**

The health benefits of nuts and seeds are summarized in **Table 5**. The evidence is robust. The benefits of nuts have been seen in at least 20 different cohorts, including populations at least from the USA, Europe, Iran, and China over a period of more than 26 years. The benefits from one or two ounces of nuts per day are substantial —20% reduction in all-cause mortality, 30% reduction in death by heart disease, 18% reduction in stroke death, 39% reduction in type 2 diabetes death and a 13–15% reduction in


#### **Table 5.**

*Summary of health benefits of nuts and seeds.*

cancer death. Optimal results will be realized by optimizing all aspects of dietary and lifestyle choices, but the inclusion of a serving of nuts per day appears to be a wise choice.

#### **4. The safety of nuts and seeds when dealing with cancer**

There is one remaining issue to address here. The evidence above indicates that nuts help prevent some cancers, but what is the role of nuts and seeds after diagnosis, or during treatment or remission of cancer?

A more fundamental issue is whether dietary fats cause growth of tumors.

It is well accepted that sugar feeds cancer directly. The PET scan is done on this principle. A sugar molecule with a radiolabeled tracer on it, typically 18Ffluorodeoxyglucose, is injected into a person. Whatever part of the body is metabolizing sugar the fastest is the biggest tumor. Tumors metabolize sugar at an accelerated rate compared to the rest of the body.

Protein may also be a factor in tumor growth. Tumor cells can grow on the amino acid glutamine nearly as well as with glucose as an energy source, especially under low oxygen conditions [42–44]. The TCA cycle that produces energy can run on either glucose or glutamine especially in cancer cells.

Protein can also indirectly feed cancer through hormonal effects. High protein, especially animal protein, raises insulin levels and especially raises IGF-1 levels. IGF-1 is a growth hormone that promotes the growth of all cells. Sufficient levels of IGF-1 prevent frailty but excessive levels have been associated in several studies with higher risk of cancer incidence and death [45].

So, sugar and animal protein both contribute to tumor growth. Does dietary fat also cause tumor growth? It is well known that abdominal fat is a risk factor for cancer. Fat cells in your body produce inflammatory substances. Being overweight or obese is a risk factor for cancer. It has already been established that nuts and seeds do not contribute to obesity in populations that habitually consume them daily.

It turns out that the source of dietary fat makes a difference. It always has, even in the Seven Countries Study on fat and international rates of heart disease deaths [46]. When the analysis is separated into plant fats and animal fats the animal fats appear to be associated with disease, but not plant fats. More recent studies have also found this effect.

In recent analysis of data from two large cohorts of the USA population, the Nurses' Health Study and the Health Professionals Follow-Up Study, the source of MUFAs was separated into plant and animal source. Guasch-Ferré et al. found the MUFAs from plants were associated with lower total mortality and the MUFAs from animals were associated with higher total mortality [47]. Just the opposite effects were seen, depending on the source of the fats. This would indicate that MUFAs from nuts are not in the same category as MUFAs from animal products.

Another recent article also highlighted the difference between MUFAs from plants or animals. The results of analyzing 16 years of follow-up of the NIH-AARP Diet and Health Study with about 520,000 people were that cardiovascular mortality was positively associated with saturated fats, trans fats, arachidonic acid (from animal foods), and animal-sourced MUFAs and was inversely associated with marine omega-3 PUFAs, linoleic acid (omega 6 oil from plants), and plant-sourced MUFAs [48].

So, plant fats are different from animal sourced fats for health outcomes. When looking at the question of whether fat accelerates tumor growth, the source of the fat has to be considered.

A direct answer to our question of the safety of nuts for cancer patients is also available. In a prospective study of colon cancer patients who were enrolled in a randomized adjuvant chemotherapy trial, those that ate two or more servings of tree nuts per week during the 6.5 years of follow-up had a 46 percent improvement in

*The Beneficial Role of Nuts and Seeds in a Plant-Based Diet DOI: http://dx.doi.org/10.5772/intechopen.110677*

disease-free survival rate and a 53 percent improvement in overall survival [49]. This analysis controlled for other known or suspected risk factors for cancer recurrence, so it appears that the effect is from the nuts themselves. So in this group of cancer patients the ones who ate nuts lived longer without disease and lived longer overall.

Hallelujah Acres and others have advocated the use of flax seeds for cancer patients. The lignans in the fiber of the flax seeds are metabolized into enterodiol and enterolactone, which are well known for reducing cancer risk [50]. Ground flax seeds are considered by many to be a superfood, but while flax seeds are unique, they are a high fat food that has much in common with other nuts and seeds. Sesame seeds also are a precursor source of enterodiol and enterolactone [51]. Other nuts and seeds have phytochemicals in them that appear to be protective to those who eat them as well.

So, the scientific evidence says that nuts and seeds are not only safe, but beneficial in every stage of life, including while battling with cancer. Populations who eat nuts have lower rates of cancer, MUFAs from plants are protective from disease, as opposed to MUFAs from animal sources, there is no clear mechanism for dietary plant fats to accelerate the growth of tumor cells, and a recent clinical trial has shown that intake of nuts by colon cancer patients undergoing chemotherapy had better diseasefree survival and overall survival.

#### **5. Conclusion**

Let us quickly review the answers to our original queries.


#### **Acknowledgements**

A special thanks to Olin Idol for constructive conversations and suggestions for improving this manuscript.

### **Conflict of interest**

The author declares no conflict of interest.

### **Author details**

Michael S. Donaldson Hallelujah Acres, Zillah, USA

\*Address all correspondence to: mdonaldson@myhdiet.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*The Beneficial Role of Nuts and Seeds in a Plant-Based Diet DOI: http://dx.doi.org/10.5772/intechopen.110677*

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#### **Chapter 2**

## African *Moringa stenopetala* Plant: An Emerging Source of Novel Ingredients for Plant-Based Foods

*Anteneh T. Tefera, Debebe Worku Dadi, Alemayehu Getahun, Asaminew Abiyu, Alphonsus Utioh, Diriba Muleta, Rotimi E. Aluko and Mulualem T. Kassa*

#### **Abstract**

*Moringa stenopetala* is a multi-purpose tropical plant native to East Africa. The plant is exceptionally rich in nutrients and health-promoting bioactive compounds. It is among the top plants that could potentially feed the world and alleviate nutritional deficiencies. *Moringa stenopetala* is a versatile plant because its various parts, including leaves, seeds, flowers, pods, bark, and roots are useful to humans. Especially, the leaves and seeds are high in protein with all the essential amino acids. Based on the FAO database, *M. stenopetala* seed protein with its essential amino acid content stands highest among all commercial plant protein sources. Though it is a high-value plant and extensively used for food and traditional medicine by the local people in its native place, it is underutilized elsewhere. This chapter reviews recent research efforts that aim to unlock the potential of the plant as a source of ingredients for food, cosmetic and nutraceutical industries.

**Keywords:** bioactive compounds, *Moringa stenopetala*, oil, plant-based food, protein

#### **1. Introduction**

The growing awareness of the effects of food on human health and the environment has warranted a need to look for alternative food sources. This has promoted a steady increase in demand for plant-based diets [1], which can be attributed to increasing vegan, vegetarian, and flexitarian populations as well as increasing intolerance to animal proteins. Ethical concerns about animal abuse, the nutritional benefits of plant-based diets and the ever-increasing investments in the plant protein sector are all factors contributing to the growth of plant-based foods [2, 3].

The plant-based food market is expected to grow at a compound annual growth rate (CAGR) of 12.4% in 2022 to reach \$95.52 billion by 2029 [2]. The growth rate for the U.S. plant-based food market was more than doubled in 2020 as sales surged 27% to \$7 billion, according to the Plant Based Foods Association (PBFA) and Good Food Institute (GFI). To meet the increasing demand, there is a need to adopt climate-resilient food production system with higher yields of improved functional food ingredients. The versatile tropical plant species Moringa with uses for its various parts, particularly the leaves and seeds, holds immense potential for use as ingredients in plant-based food and therapeutic applications.

Moringa belongs to the monogeneric Moringaceae family [4]. The genus consists of about 14 species, including the well-known species, *Moringa oleifera*, which is native to the Indian sub-continent, and *Moringa stenopetala*, also known as African Moringa, which is endemic to East Africa [5]. The leaves and green pods of Moringa are rich in both macro and micro-nutrients and are eaten as a staple vegetable, especially in the Indian sub-continent and Africa [6].

Moringa is one of the world's most useful tropical trees and often nick-named a 'multi-purpose tree' [7, 8]. It is a resilient and highly drought-tolerant tree growing on marginalized land and almost all parts of the plant are useful [9]. The leaves, seeds, pods, flowers, and roots are excellent sources of nutrients and bioactive compounds [10, 11], especially dietary fiber, proteins, minerals, vitamins, and phytochemicals that offer great nutritional and therapeutic benefits [5, 12–14].

Moringa is listed among the top plants that could help feed the world and alleviate nutritional deficiencies and is often considered as a superfood [7, 8]. It holds much promise to serve as a source of valuable bioactive compounds for food, pharmaceutical and cosmetic applications [5]. Moringa seed hulls (often considered a waste) are used to develop high performance carbonaceous adsorbents and biological coagulants for water and wastewater treatment and removal of hazardous contaminants, which enhances environmental health [15–17].

Unlike *M. oleifera* for which there are robust scientific studies on its chemistry, food, and therapeutic uses [12, 13], only a few similar scientific studies have been conducted on *M. stenopetala* [18].

*M. stenopetala* is used as a staple food and traditional medicine by the local people in its native place in East Africa. It grows on the homesteads of small-holder farmers and is tightly linked to the livelihood of local communities in the region (**Figure 1**). The plant is exceptionally rich in nutrients and health-boosting bioactive compounds and could potentially alleviate nutritional deficiencies. The leaves and seeds are high in protein content and contain all the essential amino acids. Recent studies in Canada revealed that *M. stenopetala* seed protein with its essential amino acid content is the highest among all the commercial plant protein sources based on the FAO database (personal communication).

**Figure 1.** Moringa stenopetala *in Konso, Southern Ethiopia.*

*African* Moringa stenopetala *Plant: An Emerging Source of Novel Ingredients for Plant-Based… DOI: http://dx.doi.org/10.5772/intechopen.112213*

Though the plant holds much promise as a source of ingredients for nutrient-and mineral-rich plant-based diets, it is less known to the outside world and rarely utilized in food product formulations. Thus, this chapter reviews recent research interests that aim to uncover potential uses of *M. stenopetala* ingredients for plant-based food and therapeutic applications.

#### **2. Origin, ecology, and production of** *M. stenopetala*

*M. stenopetala* is native to east Africa, with diversity spanning Ethiopia, Kenya, and Central Somalia [19]. In Ethiopia, the distribution of the species is mostly concentrated in specific zones in the south [20–23]. The presence of *M. stenopetala* has also been reported in the northern part of the country, specifically in Alamata district of southern Tigray, where it is promoted as an agroforestry tree species [24].

*M. stenopetala* grows in Ethiopia from 390 to 2200 meters above sea level (mas) in the southern Rift Valley, including the arid and semi-arid regions between 1000 and 1800 mas [23, 25]. *M. stenopetala* grows well in areas receiving annual rainfall and temperature that ranges from 250 to 1500 mm and 25°C to 35°C, respectively. According to a summary of the national herbarium's vouchers, the habitat where the genus occurs in Ethiopia consists of rocky riverbanks, dry scrub land, Acacia-Commiphora woodland, watercourses with some evergreens, open Acacia Commiphora bush land on gray alluvial soil, and cultivated lands in and around villages.

*M. stenopetala* is intercropped with food crops in moderately dry regions of southern Ethiopia and used as a farm tree (home gardens) to support the livelihoods of the high population present in the region. It is among the most useful trees planted and managed by rural people in the dry areas of Ethiopia [7, 26]. With proper agronomic practices, *M. stenopetala* has the potential for large-scale commercial farming. It was reported that a single tree of *M. stenopetala* could support a large family for several years [21, 27]. Thus, *M. stenopetala* is a promising plant to adopt for a climate-resilient food production system that could have a significant impact on alleviating food insecurity and serve as a source of ingredients in food and therapeutic applications.

#### **3. Nutrient and bioactive composition of various parts of** *M. stenopetala*

The nutrient, bioactive compounds, vitamin, and mineral composition of various parts of the plant, particularly the leaves and seeds, are presented in this section. The trending potential of the use of *M. stenopetala* ingredients in plant-food formulations is also highlighted. The nutritional and bioactive composition of *M. stenopetala* is presented and compared with that of *M. oleifera*, for which a wealth of information on its chemistry, nutrient and bioactive profiles and therapeutic potential is available [12, 13].

Moringa leaves, seeds, flowers, roots, and green pods are rich in macro and micronutrients. The leaves of *M. stenopetala* are popular as a staple vegetable in eastern Africa as is *M. oleifera* in the Indian subcontinent [21, 28, 29]. Dried Moringa leaf powder that is kept under dark conditions preserves the nutritional potency of the leaves for a long period of time [30, 31]. Dried leaves are utilized for the preparation of Moringa herbal tea and other non-alcoholic beverages that have significant health benefits [18].

#### **3.1 Dietary composition of the leaf**

Findings from various studies revealed that *M. stenopetala* and *M. oleifera* are rich in nutrients, minerals, vitamins, and bioactive compounds [32]. *M. stenopetala* dried leaf has a high protein content of about 28% (**Figure 2**). The protein from the leaves of *M. stenopetala* is complete and contains all the essential amino acids at levels equal to or higher than those found in soybean seeds [32, 33]. Similarly, recent research conducted in Canada found that *M. stenopetala* leaf has high protein content and contains all the essential amino acids (personal communication).

*M. stenopetala* leaf contains 28 and 160 mg/100 g of vitamin C and beta carotene, respectively [21]. Some studies have also reported the presence of other vitamins in higher amounts [21, 32]. Among many green leafy vegetables, Moringa was found to be a rich source of ß-carotene (vitamin A) and other micronutrients [34].

Leaf extracts of *M. stenopetala* have good amounts of phenolic and flavonoid compounds that have high antioxidant activities [35, 36]. Habtemariam and Varghese [18] have also reported the presence of a high amount of rutin, a bioflavonoid antioxidant that could be extracted from *M. stenopetala*'s dried leaves.

Previously published papers demonstrated that the minerals found in Moringa leaves are diverse and abundant. *M. stenopetala* leaves had 3363 mg/100 g of potassium, which was 3.96 times higher than in banana fruit (933 mg/100 g) [37]. Banana fruit is one of the foods recommended as a source of potassium and calcium [38]. *M. stenopetala* dried leaf is rich in calcium, potassium, magnesium, iron, phosphorus, and zinc but characterized by its low content of sodium [37]. *M. stenopetala* is nutrient-rich but low-calorie food and is an ideal part of a diet designed for body weight management.

#### **3.2 Composition of** *M. stenopetala* **seed**

Different research results have reported protein (28–43%) and oil (33–41%) levels from *M. stenopetala* seeds. *M. stenopetala* seeds are a great source of protein, high-quality edible oil, and numerous other beneficial compounds [12]. Studies have shown high protein content and considerable levels of essential amino acids in

#### **Figure 2.**

*Nutrient composition (%) of* Moringa stenopetala *dried leaves (adapted from authors indicated on the above chart).*

*African* Moringa stenopetala *Plant: An Emerging Source of Novel Ingredients for Plant-Based… DOI: http://dx.doi.org/10.5772/intechopen.112213*

Moringa seeds [12]. Results of different studies on the amino acids exhibited high qualities of the seed protein [39, 40]. Various studies have shown that the protein from Moringa seeds contains all nine essential amino acids, making it one of the best sources of plant-based proteins [12, 41, 42].

The amino acid composition of Moringa seed was compared to the hen's egg used as the reference by the FAO [43], and assessed the protein quality using the individual amino acid score. The results of this study showed that Moringa seed proteins have higher amounts of total amino acids and fewer amounts of total essential amino acids than hen's egg protein, revealing the potential use of Moringa seed protein in food applications.

According to the report, 45% of *M. stenopetala* seed is oil, with 78% of the fatty acid composition being monounsaturated (of which 76% is oleic) and 22% is saturated fatty acids [22]. *M. stenopetala* seed oil has an average value of oil density (0.919 kg/cm3 ), specific gravity (0.918 g/cm3 ), peroxide value (11.52 millieq O2/kg), viscosity (19 mPa.s), acid value (3.74 mg KOH/g) and ester value (177.2 mg KOH/g) [44, 45]. According to Vaknin and Mishal [46], the saturated fatty acids present in Moringa oil include palmitic acid, stearic acid, arachidic acid, and behenic acid. The unique fatty acid and bioactive components, combined with distinct physiochemical properties, make *M. stenopetala* oil an ideal ingredient for food, pharmaceutical, cosmeceutical, and therapeutic applications [43, 47].

#### **3.3 Pods and other parts**

*Moringa stenopetala*'s flower, pod, and roots have received much less attention and are less known than the leaves and seeds. The protein, fiber, and ash contents of the pods of *M. stenopetala* and *M. oleifera* were 18 and 17%, 37 and 36%, and 12 and 10%, respectively [48]. The authors have also reported the mineral contents of pods of *M. stenopetala* and *M. oleifera* (**Figure 3**) with the further remark that the flowers, pods, and roots of Moringa contain appreciable concentrations of minerals and nutrients. Therefore*, M. stenopetala* enhances dietary diversification and thus has a significant impact on mitigating hunger in developing countries.

#### **4. Health benefits of** *Moringa stenopetala* **diet**

The health benefits of *M. oleifera* are well documented in recent research reports [12, 13]. Though we have a dearth of information, some studies have also shown the nutritional and health benefits of *M. stenopetala*. Different parts of the plant are traditionally used to treat hypertension, diabetes, malaria, common cold, asthma, wounds, retained placenta, and stomach-ache [49, 50]. The leaf extracts of *M. stenopetala* have shown antihypertensive effects and antidiabetic activity [51, 52]. Furthermore, hepato- and kidney protective effects of Moringa leaf extracts were also reported [53]. This might be due to the presence of protective action against lipid peroxidation and reactive oxygen species of the plant's extract, which can be attributed to the presence of phenolic and flavonoid compounds [18, 54]. *M. stenopetala* leaf extract also has a high content of rutin, a powerful bioflavonoid [18]. These compounds exhibit higher antioxidant activity and are claimed to be responsible for several beneficial biological activities.

Diabetes mellitus is a complex metabolic disease that is a major global public health concern. Diabetes is increasing at an alarming rate all over the world and its prevention will necessitate measures to promote a healthy dietary pattern. Studies revealed that *M. stenopetala* leaf extract has the potential to reduce blood glucose levels effectively [55, 56]. Serum glucose level was also decreased significantly after 6 weeks of treatment of mice with *M. stenopetala* leaf extract [57]. In addition, microencapsulated products developed from *M. stenopetala* leaf extracts have shown a significant effect on diabetes [52]. The leaf of *M. stenopetala* also has a high dietary fiber [21], which may help in the prevention and management of diabetes. Furthermore, the phenolic compounds, vitamin E and tannins, present in *M. stenopetala*, can also help to reduce the risk of diabetes by managing blood glucose levels.

*M. stenopetala* leaf extract showed an antihypertensive activity as it was found from the result of vasodilator and urinary excretion increment [52]. The decreased blood pressure, extracellular fluid volume, and cardiac output occurred due to diuretics, which increase the urinary sodium excretion, thereby reducing the plasma volume that controls hypertension [58]. *M. stenopetala* leaf extract has shown significant diuretic activity [51, 52], consequently it has the potential to act as an antihypertensive agent.

The relaxation of the smooth muscle of blood vessels (vasodilation) favors normal blood pressure. However, if this blood vessel is contracted, relaxation is required using nitric oxide [59]. It was found that *M. stenopetala* leaf extract has a high relaxation (99.13%) against potassium chloride induced contraction of the guinea pig thoracic aorta at a concentration of 40 mg/mL [52]. Oral administration of the aqueous extract of *M. stenopetala* leaves led to significant reductions in systolic blood pressure, diastolic blood pressure and mean arterial blood pressure [16].

It is claimed that *M. stenopetala* has anti-carcinogenic activities due to the presence of glucosinolate compounds [60]. In addition, *M. stenopetala* leaf extract contains polyphenols and flavonoids that give a synergistic effect to anti-carcinogenic activities [54, 60].

#### **5. Trends of** *Moringa stenopetala* **use in food and nutraceutical applications**

*M. stenopetala* is emerging as a trending source of novel ingredients in the food, pharmaceutical and skin care industries. The dried leaves are used to formulate health-boosting herbal tea, the dried leaf powder is a source of nutrient-dense

*African* Moringa stenopetala *Plant: An Emerging Source of Novel Ingredients for Plant-Based… DOI: http://dx.doi.org/10.5772/intechopen.112213*

#### **Figure 4.**

*Commercialized herbal tea, leaf protein powder, seed oil and moisturizing facial cream developed from*  M. stenopetala *leaves and seeds through research and development project in Canada (Photo credit: BioTEI Inc.).*

ingredient for food applications, and the seed oil is used by the food and skin care industries (**Figure 4**). After the oil is extracted from the seed, it leaves a protein-rich press cake as a secondary extraction product.

The seeds of *M. stenopetala* are good sources of edible oil and flocculent agents for water purification as well as biofuel [49]. It was found that the protein content of *M. stenopetala* seed was higher than the protein content of other oilseeds and pulses [45]. This shows that *M. stenopetala* seeds can be utilized as a potential protein source to combat malnutrition in developing countries and as an ingredient for food applications in general. *M. stenopetala* seed oil yield reaches about 44% [61], which can be considered as a major source of oil that could be used for cooking, salad dressing, and cosmetics applications. Moringa oil is also known as ben oil and has been reported to have physical and chemical properties comparable to olive oil with a high concentration of tocopherols and oleic fatty acid [61]. Thus, this oil has better oxidative stability, which can be used in the food industry for longer storage and high-temperature frying. Furthermore, *M. stenopetala* seed oil has excellent absorbing properties on the skin which makes it a vital ingredient for the cosmetic industry. Moringa oil also has anti-aging properties due to its key bio-agents that could maintain moisture and promote the mechanical elasticity and flexibility of the skin [62]. These findings indicate that *M. stenopetala* seed oil is an ideal candidate for the pharmaceutical and cosmetics industries manifesting its untapped multifaceted business potential.

#### **5.1 Food fortification**

*M. stenopetala* enhances dietary diversification and thus has a significant impact on mitigating hunger in developing countries. The leaves are consumed as cabbage and the dried powder is used as a dietary supplement for proteins, calcium, iron, phosphorous as well as vitamins [63, 64]. The essential amino acids concentration of *M. stenopetala* leaves is comparable with that of defatted soybean seed meal [63]. The author has also reported the metabolizable energy, organic matter digestibility, and short chain fatty acids contents. *M. stenopetala* is a rich source of micronutrients that are commonly deficient in cereal-based diets. The concentrations of essential minerals in *M. stenopetala* leaf are very high [7], indicating its superiority to other staple foods grown in Ethiopia (**Table 1**). Moreover, cooking improved the digestibility of protein


**Table 1.**

*Medial elemental concentrations in* M. stenopetala *leaves and other food sources grown in Ethiopia.*

by 20.7 and 7.8% in leaves and pods, respectively; the same trend was observed for the total carbohydrates [64]. These authors have also confirmed the importance of cooking the leaves and pods of *M. stenopetala* for the reduction of tannins (a known anti-nutritional factor) by 27 and 45%, respectively.

The essential amino acids concentration of *M. stenopetala* leaves is comparable with soybean seed meal content [63]. The author has also reported the metabolizable energy, organic matter digestibility, and short-chain fatty acids contents. The leaves of *M. stenopetala* leaves have also relatively high phenolic and flavonoid compounds [18] indicating their antioxidant properties with a health-promoting effect on consumers [54]. Plant-derived bioactive components such as phenolic compounds inhibit the formation of free radicals, thereby preventing the formation of hydroperoxides. However, these bioactive components are lost during food processing using the conventional thermal approach. As a result, fortification is necessary to restore these bioactive components to the final food products, this makes Moringa an incredible ingredient in food fortification.

#### **5.2 Functional and nutraceutical applications**

The presence of phenolic and flavonoid compounds helps to prevent oxidative damage. Currently, synthetic antioxidants are reported to be associated with carcinogenic effects; as a result, consumers' interest in natural antioxidant sources is increasing. Nutraceutical, functional foods and pharmaceutical product development have created opportunities for these emerging ingredients derived from Moringa. Functional and nutraceutical products development from *M. stenopetala* extract is a promising strategy to maximize the utilization and industrialization of this underutilized but highly versatile plant. Due to its richness in proteins [63], β-carotene, other bioactive compounds, and antioxidant properties [54] and a high selenium concentration, this plant has untapped potential in human health enhancement [7]. Hence, *M. stenopetala* has the potential to be used as a key ingredient in functional foods and nutraceutical product development.

Environmental variables, storage conditions, and thermal processing, all contribute to the easy degradation of nutritional and bioactive components in *M. stenopetala*. Therefore, it is important to find alternative methods to maintain and improve the stability of these compounds. Product development from *M. stenopetala* is also important to improve the storage stability of the harvested plant parts. Spray-drying

*African* Moringa stenopetala *Plant: An Emerging Source of Novel Ingredients for Plant-Based… DOI: http://dx.doi.org/10.5772/intechopen.112213*

microencapsulation of *M. stenopetala* leaf extract using a mixture of maltodextrin and pectin as a coating material is more efficient for the food and pharmaceutical industries than other processes [65]. A microencapsulated product developed from *M. stenopetala* leaf extract showed significant antidiabetic and antihypertensive effects. According to the findings, the percentage of urinary excretion was increased with the increment of the dose of the microencapsulated bioactive product developed from *M. stenopetala* leaf extract [52]. This shows that microencapsulated products have significant diuretic activity. Thus, this microencapsulated product may be used to minimize the abnormal accumulation of fluid in the human/animal body which in turn helps to manage hypertension.

#### **5.3 Antimicrobial properties**

Endemic plants, like *M. stenopetala*, are good sources of new antimicrobial compounds that might be effective against microorganisms resistant to commonly prescribed antimicrobials. The leaves/seeds extract from *M. stenopetala* have shown antimicrobial properties. According to Mekonnen and Dräger [60], *M. stenopetala* seed oil extract inhibited the growth of some pathogenic microorganisms such as *Staphylococcus aureus*, *Salmonella typhi*, *Shigella* spp. and *Candida albicans.* Similarly, leaf extracts of *M. stenopetala* using a mixture of methanol and chloroform have significant inhibitory activity against *Klebsiella pneumoniae* and *Bacillus cereus* [66]. Thus, it is important to develop antimicrobial products from *M. stenopetala* as an alternative bio-preservative to improve the shelf stability of some perishable food products.

#### **5.4 Other industrial applications of** *Moringa stenopetala* **by-products**

The seed husk and defatted seed press cake of *M. stenopetala* could be used to develop valuable bio-products (e.g., activated carbons and biological coagulants) that could be utilized in water and wastewater treatment applications that considerably promote a circular economy to enhance environmentally safe clean technology.

#### **6. Conclusion**

The African endemic Moringa tree, *M. stenopetala* is well regarded as a beneficial botanical with exceptionally high nutritional and health benefits to humans and thus nicknamed 'the multipurpose tree'. It is highly drought-tolerant and suitable for climate-resilient sustainable food production. Almost all parts of the plant (leaves, flowers, pods, seeds and hulls) have uses in the food, cosmetic and pharmaceutical industries due to their high contents of nutritional and essential bioactive components. Moringa seed oil has a good fatty acid profile suitable for food and cosmetic applications while the press cake (by-product of oil extraction) is rich in protein with good amino acid profile, and dietary fiber, making it a good raw material for protein extraction for the plant-based food industry. The leaves are dried to produce herbal tea, but they can also be ground into nutrient-dense ingredients for the development and fortification of various food products including smoothies, bars, and chips. The hulls can be used to produce activated carbon for water and wastewater treatment. Moringa is a multi-functional plant that is good for human nutrition, environmental health, and plays a pivotal role in economic sustainability of the population. However, more research is required to realize the full potential of *M. stenopetala* through the development of extraction technologies for seed protein and its hydrolysates and fractionated peptides. Research on development of food, cosmetic and nutraceutical products with Moringa ingredients will allow consumers to fully benefit from the nutritional and bioactive components of this African "miracle" tree.

### **Acknowledgements**

The authors thank the National Research Council Canada (NRC)- IRAP program for its support through contribution agreement with BioTEI Inc.

### **Author details**

Anteneh T. Tefera1,2, Debebe Worku Dadi3 , Alemayehu Getahun4 , Asaminew Abiyu5 , Alphonsus Utioh6 , Diriba Muleta<sup>2</sup> , Rotimi E. Aluko7 and Mulualem T. Kassa1 \*

1 BioTEI Inc., Winnipeg, Manitoba, Canada

2 Institute of Biotechnology, College of Natural Sciences, Addis Ababa University, Ethiopia

3 Department of Food Process Engineering and Postharvest Technology, Institute of Technology, Ambo University, Ethiopia

4 Wachemo University, Hosaena, Ethiopia

5 College of Environmental Science and Engineering, Donghua University, Shanghai, China

6 ACU Food Technology Services Inc., Portage la Prairie, Manitoba, Canada

7 Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, Canada

\*Address all correspondence to: mtkassa@bioteinnova.ca

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*African* Moringa stenopetala *Plant: An Emerging Source of Novel Ingredients for Plant-Based… DOI: http://dx.doi.org/10.5772/intechopen.112213*

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[61] Haile M, Duguma HT, Chameno G, Kuyu CG. Effects of location and extraction solvent on physico chemical properties of *Moringa stenopetala* seed oil. Heliyon. 2019;**5**(11):e02781. DOI: 10.1016/j. heliyon.2019.e02781

[62] Xu Y, Chen G, Guo M. Potential antiaging components from *Moringa oleifera*

leaves explored by affinity ultrafiltration with multiple drug targets. Frontiers in Nutrition. 2022;**9**:854882. DOI: 10.3389/ fnut.2022.854882

[63] Melesse A. Comparative assessment on chemical compositions and feeding values of leaves of *Moringa stenopetala* and *Moringa oleifera* using in vitro gas production method. Journal of Applied Science and Technology. 2011;**2**(2):31-41

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#### **Chapter 3**

## Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations

*Ntsoaki Joyce Malebo*

#### **Abstract**

Globally, communities experience food insecurity, highlighting a need for access to food sources that are readily available with nutritional benefits. African leafy vegetables represent a plant-based food source that is rich in nutritional content and health benefits. These vegetables can grow unattended in the wild with minimal agricultural inputs which may negatively affect the environment, highlighting the advantages of their use. However, there is still a need to investigate the nutritional and functional value of these vegetables, focusing on their advantages and limitations before they can be recommended as an alternative food source. The chapter will focus on evaluating peer-reviewed journal articles, book chapters, and other publications to conduct a qualitative review.

**Keywords:** nutritional value, functional value, African leafy vegetables, plant-based diet, nutritional benefits

#### **1. Introduction**

The literature demonstrates that the Southern African Development Community (SADC) region is warming up faster than other regions in the global North prompting action towards adaptation strategies. The SADC region has observed adverse changes in rain patterns resulting in floods or multiple droughts. Reports by the Food Agriculture Organization [1] indicate the doubling of areas on the planet affected by droughts over a 40-year period [2]. The observed threat is a concern as the most vulnerable communities affected by high levels of unemployment, poverty, malnutrition, and inequality can be found in the SADC region. Studies indicate that climate change threatens health, ecology, and food security in sub-Saharan Africa [3, 4]. For ecology, an increase in woody vegetation has been observed which continues to replace indigenous habitats in certain regions [3]. The rise in temperatures leads to increased levels of evapotranspiration [5] which may affect food production and highlights the need to increase the propagation of climate-resilient crops such as African leafy vegetables (ALVs). Furthermore, because ALVs are considered climateresilient crops, they can support climate adaptation strategies that are needed to address food insecurity [2]. Researchers [4] further argue that science interventions

should be linked with local indigenous knowledge for adaptation and food security to address challenges such as climate change.

Maseko et al. [6] contend that the addition of ALVs in cropping systems can contribute to climate change adaptation strategies. This argument is supported by Nyathi et al. [7] who advocate for the diversification of current food production systems because vegetables such as Swiss chard which are available in commercial markets require high cultivation input whereas ALVs grow easily in the wild with minimal input from fertilizers and water. It has also been demonstrated that as climate changes, the presence of additional carbon dioxide in the air enhances the drought adaptation mechanisms of ALVs such as stomatal conductance which enables their growth during times of drought. This ensures the availability of highly nutritious vegetables which can support a plant-based diet.

Although commercially available C3 vegetables such as Swiss chard increase biomass when carbon dioxide levels increase, their propagation requires high water input and fertilizers when compared to ALVs [8]. This indicates that such commercially available vegetables would not support climate adaptation strategies. Furthermore, an increase in carbon dioxide reportedly has a direct effect on nutrition as it reduces iron, zinc, and protein content in grains [4, 8], this implies that an increase in biomass may not result in high nutritional content. ALVs are recognized as a rich source of minerals and vitamins which are currently not available in commercially accessible vegetables [9–11]. Despite the known nutritional benefits of ALVs, urbanization, access to disposable income, and availability of commercial vegetables continue to influence changes in diet patterns in favor of commercial vegetables over ALVs [2]. In most African communities, ALVs are still regarded as weeds or food for the poor. Researchers argue that ALVs can be used in what is referred to as "hidden hunger" which is defined as micronutrient deficiencies [10, 12] observed globally due to a preference for ready-to-eat foods with limited nutritional value.

#### **2. Methodology**

A review of existing databases (Google Scholar, Science Direct, Web of Science, Scopus) was conducted for data published on ALVs from 2010 to 2023. Keywords such as "African leafy vegetables", "indigenous leafy vegetables", "nutritional value", and "functional value" were used to search for open access journal papers and book chapters. Inclusion criteria: Reviews and experimental papers published in peer-reviewed journals, book chapters, and conference proceedings between 2010 and 2023 were selected. Exclusion criteria: papers published prior to 2010 and not in peer-reviewed publications from sub-Saharan Africa. A total of 80 articles were retrieved and relevant papers were selected and used for the current review. Study limitations: The current study was limited to publications in peer-reviewed journals and book chapters, other studies published in non-peer-reviewed papers and also in other languages may have been excluded. The study also focused on ALVs mainly consumed in countries within sub-Sahara Africa and may have excluded leafy vegetables consumed in other parts of the African continent including the studied areas.

#### **3. Type of African leafy vegetables (ALVs) consumed by communities**

Different types of African leafy vegetables (ALVs) are consumed in various countries in sub-Saharan Africa. In Zimbabwe, ALVs such as *Cleome gynandra*, *Amaranthus*  *Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations DOI: http://dx.doi.org/10.5772/intechopen.112972*

*thunbergii* Moq, *Vigna unguiculata*, *Corchorus tridens*, *Corchorus olitorius*, *Bidens pilosa,* and *Amaranthus hybridus* are consumed [13]. *Cleome gynandra* also known as African cabbage belongs to the family Capparaceae, an erect herb with palmately compound leaves (**Figure 1A**). *Amaranthus* species (**Figure 1B**), from the Amaranthaceae family, leaves are described as succulent and simple in some taxa. *Vigna unguiculata* is classified in the Leguminosae family and distinguished from other ALVs by tri-foliate leaves. *Corchorus* (**Figure 1C**) species belongs to the Tiliaceae family, with oblong to lanceolate leaves that have serrated margins and distinct hair-like teeth at the base. *B. pilosa* belongs to the family Asteraceae, differentiated by lobed, serrate, and opposite green leaves, and yellow or white flowers (**Figure 1D**).

According to [13], *C. gynandra* (Cleomaceae family) and *Vigna unguiculata* (Fabaceae family) are considered amongst the top five most important traditional vegetables in Zimbabwe. Although these vegetables are important traditional food sources, other species such as *B. pilosa* (Asteraceae family) are used not only as a food product but as medicine [14] based on the indigenous use of the plants. *B. pilosa* L. [15] is reportedly used to treat malaria, dysentery, diarrhea, and infected wounds or burns [16]. Most of these ALVs grow in the wild with minimal production input but [13] that vegetable species such as *C. gynadra* have been reportedly domesticated in home gardens and are purposely protected during activities such as digging, weeding, and land clearing due to the known benefits they provide.

Although ALVs grow in the wild, a study by [17] indicated that species such as *Amaranthus hybridus* and *C. gynandra* occur in all soil types, however, *C. gynandra*

**Figure 1.**

*An image showing selected ALVs. A – Cleome gynandra; B – Amaranthus thunbergii; C – Corchorus olitorius and D – Bidens pilosa.*

#### **Figure 2.**

*An image of ALVs showing A – Solanum spp.; B – Talinum; C – Acalypha; D – Celosia; E – Sesammum; F – Urtica.*

tends to be associated with sandy soils. Although *B. pilosa* reportedly thrives in any environment [14], it can be negatively affected by frost. Nightshade (*S. retroflexum* Dun.; Solanaceae family) leaves and tender shoots are consumed in most African countries [18]. African leafy vegetables mainly consumed in South Africa include *Amaranthus* species [6] such as *Amaranthus thunbergii* Moq., *Amaranthus spinosus* (L.) followed by *Corchorus* (*C. asplenifolius*, *Corchorus trilocularis*, *C. tridens* and *C. olitorius*), *Cleome monophylla* L. (*C. monophyla*, C. hirta) [19], *Vigna unguiculata,* and *Bidens pilosa* [20]. *Cleome gynandra*, *Curcubita maxima*, *Vigna unguiculata*, *Vigna unguiculata subsp. dekindtiana* var. *dekindtiana*, *V. unguiculate* subsp. *dekindtiana,* var. *huillensis*, *V. unguiculata* subsp. *rotracta*, *V. unguiculata* subsp. *stenophylla*, *V. unguiculate* subsp. *tenuis* var. *ovata*, *V. unguiculata* subsp. *unguiculata*, *Vigna unguiculata* subsp. *unguiculata, Solanum nigram*, *Urtica urens*, *Ribe*s *uva crispa*, *Taraxacum officianale,* and *Beta vulgaris* [21] which are rich in nutrients, are also consumed in South Africa.

*Solanum macrocarpon*, *Talinum fruticosum*, *Corchorus* (**Figure 2**), and *Amaranthus* are consumed in Ghana [22]. In Côte d'Ivoire, although there are various ALVs consumed, the main reported vegetables include *Acalypha ciliate*, *Celosia trygina*, *Cleome gynandra*, *Solanum nigrum,* and *Sesammum radiatum*. In Southern Angola, *Bidens pilosa* and *Amaranth* are reported as the main ALVs consumed amongst the various vegetables reported [23]. The literature demonstrates that certain species from genera *Amaranth*, *Cleome*, *Bidens*, *Vigna*, *Solanum,* and *Corchorus* are readily available in most African communities. In most of these communities, although consumption continues to decrease, the nutritional benefits of the ALVs are recognized.

#### **4. Nutritional benefits**

African leafy vegetables are generally characterized by an abundance of carbohydrates, low protein, and fat content (**Table 1**). When consumed with high-calorie

#### *Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations DOI: http://dx.doi.org/10.5772/intechopen.112972*

vegetables such as maize, supplementation for protein is needed to fully address malnutrition. Other studies have shown that adding peanut butter during cooking of ALVs enhances the presence of proteins and oils [26]. Generally, ALVs contain high amounts of flavonoids (**Table 1**) which are associated with health benefits such as protection against cardiovascular diseases, stroke, and cancer [22]. Additionally, ALVs contain moisture levels which are similar to commercially available leafy vegetables that are generally accepted by consumers [26]. The ash contents of *C. gynandra* and *Amaranth* [24] indicate that both vegetables may be good sources of minerals. The ALVs are considered sources of crude fiber which assists in the absorption of excess cholesterol.

Doue et al. [26] reported the presence of carotenoids in *Acalypha ciliate*, *Celosia trygina*, *Cleome gynandra*, *Solanum nigrum,* and *Sesammum radiatum* (**Table 1**). Although cooking methods may affect carotenoid content, the carotenoid content identified in these ALVs remains higher than what is reported for commercially available vegetables. Carotenoid pigments which include beta-carotene have high antioxidant properties which play an important role in reducing the occurrence of cancer. Additionally, vegetables with antioxidant properties can be used for the prevention of degenerative diseases [22]. African nightshade is one of the ALVs which reportedly


#### **Table 1.**

*Nutritional composition of selected ALVs.*

serves as a rich source of minerals such as potassium, manganese, and vitamins in the form of Vitamin A and folate [18]. Other studies indicate that African nightshade is a source of protein, minerals, and beta-carotene which is reportedly higher than commonly consumed vegetables [10, 12, 29]. Other vitamins identified in African nightshade include thiamine, riboflavin, and folate [12, 28].

*Amaranth* is recognized as a good source of pro-vitamin A [25] which are carotenoids that the body convert to vitamin A. Potassium, calcium, magnesium, phosphorus, iron, manganese, and zinc were identified in high amounts in *Cleome* leaf tissue [27]. Vitamins such as beta-carotene, vitamin A, vitamin C and medium in vitamin E and protein have also been reported in blackjack [14]. Minerals identified in blackjack include calcium, phosphorus, sodium, manganese, copper, zinc, magnesium, and iron [14]. The minerals are beneficial for human health with iron playing an important role in blood production [18]. The presence of high carbohydrate content in leafy vegetables indicates a high caloric content, a study conducted by [22] showed a high carbohydrate content in dried *Solanum macrocarpon, Talinum fruticosum*, *Corchorus olitorius* and *Amaranthus* spp. when compared to other studies. Crude fiber was observed by [22] in dried *Solanum macrocarpon*, *Talinum fruticosum*, *Corchorus olitorius,* and *Amaranthus*; the study further showed that these dried ALVs are good sources of protein. However, other studies observed minimal amounts [26] of protein in ALVs.

#### **5. Functional properties**

Various studies have demonstrated that traditional leafy vegetables possess phenols (gallic acid) and flavonoids which grant these vegetables various functional properties. Obeng [22] showed that *Solanum macrocarpon*, *Talinum fruticosum*, *Corchorus olitorius,* and *Amaranthus* spp. possess phenols and flavonoids. Obeng [22] reported antioxidant properties when dried *Solanum macrocarpon*, *Talinum fruticosum*, *Corchorus olitorius,* and *Amaranthus* spp. were assessed. Although antioxidant properties were identified, the study reported that high quantities of ALVs and frequent consumption are recommended to provide consumers with the reported health benefits. Nightshade possesses antioxidant properties due to the presence of phenolic metabolites [18, 30]. Jiménez-Aguilar and Grusak [31] demonstrated that some *Amaranth* species possess antioxidant properties which are higher than properties reported in spider flower (**Table 2**), African nightshade, and spinach. Although additional studies are needed, [14] have reported that blackjack possesses antioxidant properties. The health benefits of vegetables with antioxidant properties have been demonstrated.

Blackjack possesses various chemical compounds such as astragalin, a flavonoid found in various plants, reportedly has anticandidal activity. The compound was shown to inhibit fungous biofilm development. Kissanga et al. [23] indicate that *A. hybridus* is used for medicinal properties in Angola. Antibacterial properties of blackjack against gram-negative *E. coli* as well as antifungal properties have been reported [14]. In addition to the identified antimicrobial properties, blackjack has been used to treat various diseases such as indigestion, diarrhea, dysentery, wounds, and respiratory infections [14]. One of the bioactive compounds, astragalin, isolated from blackjack reportedly has anti-parasite properties against *Trigonoscuta cruzi* [14]; it affects the growth of the parasite by changing the morphology of the cell membrane.

Mtenga and Ripanda [14] also report that blackjack possesses anti-inflammatory properties due to the presence of squalene. Mokganya and Tshisikhawe [15] further


*Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations DOI: http://dx.doi.org/10.5772/intechopen.112972*

#### **Table 2.**

*Functional properties of selected African leafy vegetables.*

indicate that liquid extracted from blackjack has been used to treat inflammation and wounds as it contains antimicrobial compounds such as Iso-Vanillin and Daucene. Similar properties were reported in nightshade due to the presence of phenolic metabolites such as chlorogenic acids [18, 32]. *C. gynandra,* which is commonly used by various African communities, is characterized by compounds such as quercetin glycosides that possess anti-inflammatory properties, and claims by communities indicate that decoctions are consumed orally to reduce blood pressure [15]. Other commonly

used ALVs such as *S. retroflexum* L. are reportedly used to treat earache in young children [15] because the ALV contains hydroxycinnamic acid derivatives with antimicrobial and anti-inflammatory properties (**Table 2**). *V. unguiculata* L. is used to treat stomach problems [15] because it possesses compounds (Coumaroyl derivatives) with anti-inflammatory and anti-microbial properties. Researchers reported antidiabetic, anti-obesity, and antihypertensive properties of *B. pilosa* worldwide, indicating the possibility of its application in the mitigation of diabetes, hypertension, and obesity.

#### **6. Advantages**

It is generally accepted that ALV is resistant to drought, pests, and diseases when compared to commercially available vegetables [6, 10]. Some communities are consuming ALVs as an important resource for climate adaptation strategies [12, 33] and for food security. Kissanga and others [23] reported that vegetables are used by communities during droughts because ALVs are resistant to environmental changes. The morphology of some of the ALVs such as leaves with a waxy cuticle observed in *Amaranthus* spp. protects the vegetable against rapid moisture loss. African leafy vegetables such as *Amaranthus*, *Brassica nigra*, and *Cleome gynandra* are also drought hardy because of their excellent stomatal conductance. Some ALV species such as *Bidens pilosa* have an extraordinary recovery rate after experiencing prolonged drought periods [20].

ALVs grow in the wild with low input from pesticides and fertilizers. Additionally, bioactive compounds such as alkaloids from *Bidens pilosa* can be used as organic pesticides which are environmentally friendly and biodegradable [14]; compounds from blackjack can be used to control fungal pathogens and weeds which affect plant growth. Doue et al. [26] have reported that ALVs can serve as fertilizers as they improve the growth of other plants by improving soil fertility. Economic opportunities exist to include ALVs such as *Amaranth* in bread products, the advantages of this type of postharvest processing not only provides communities with a source of nutritious bread but increases the need and value of these vegetables [2] and also provides an opportunity to sell a highly nutritious product.

#### **7. Limitations**

Despite the added advantages of ALVs, there are some limitations that affect their use. African leafy vegetables are highly perishable, and preparation and preservation approaches affect their long-term nutritional quality [6]. Preparation methods at high temperatures can affect compounds such as vitamins and minerals. This can have a negative effect on some of the reported health benefits of ALVs. Other studies indicate that alternative methods for preparation are needed and supplementation with other sources of protein and fat may be necessary to enhance the nutritional benefits of ALVs with low fat and protein content. Doue et al. [26] argue that preparation of ALV with red palm oil may enhance the availability of vitamin A which is needed to address deficiencies that are reported in the sub-Saharan region. Although steaming reduces the nutritional properties in other ALVs, [18] demonstrated that this process can significantly reduce anti-nutritive compounds in nightshade, making it the most

#### *Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations DOI: http://dx.doi.org/10.5772/intechopen.112972*

suitable processing method. Similar studies have shown that post-harvest processes can also be beneficial and assist with the release of complex minerals, enhancing bioavailability and bioactivity [12, 34].

Lack of post-harvest processing of vegetables was reported to result in loss of quantitative, nutritive, and economic value of nightshade along the supply chain [35]. Similar losses were observed in other ALVs such as *Cleome gynandra* L., *African nightshade,* and *Amaranthus* spp. Gogo and others [35] demonstrated in their study that loss due to pests and diseases occurred mainly postharvest and this is influenced by various factors which include transport of vegetables in suitable conditions, packaging, and poor handling. African leafy vegetables are highly perishable [10] and to date, different methods to prolong their shelf life are explored. Lactic acid fermentation [36] is a method commonly used by African communities which prevents the growth of spoilage microbes and increases the sensory and shelf life properties of vegetables. Although postharvest value addition opportunities exist for ALVs, their availability in small quantities affects the possibility of establishing their availability in the food production chain [2].

Poor seed quality limits propagation and affects yield which results in a focus on exotic plants rather than African leafy vegetables [20]. Stoll and others [10] have also reported poor seed quality as one of the factors which influences the availability and consumption of ALVs. The challenge continues to exist due to limited investment in research and development [12, 21, 37]. These challenges are intensified by the presence of heavy metals in ALVs due to contamination of soils. This is a concern that studies indicate may affect the advocacy and use of these vegetables [23]. The presence of antinutritional compounds such as cyanogenic glycosides, oxalates, phytates, nitrates, and tannins is one of the challenges identified that discourages the use of ALVs. However, the implementation of suitable agro-processing techniques to facilitate the elimination of antinutritive compounds should be further explored [12] if the use of ALVs is going to be promoted. Addressing the presence of antinutritional properties of ALVs is important because their presence influences the absorption of vitamins and minerals present in vegetables, reducing their value. The biggest challenge which affects the use of ALVs is the unsustainable harvesting because the vegetables are not formally cultivated [6].

Consumer acceptability and perceptions about ALVs have generally influenced their limited consumption and propagation. The availability of mainstream vegetables influences the consumption and propagation of ALVs [38]. Blackjack (*Biden pilosa*) is underutilized in sub-Saharan Africa due to its classification as a weed or a wild plant, which creates a negative perception in the community concerning the consumption of wild or weed plants [14]. The use of blackjack despite its identified benefits is hindered by its categorization as inversive species (weeds). The perceptions that exist in communities affect the marketing of ALVs as an alternative source of nutrition. There is a general agreement that ALVs are poorly marketed [10] despite the nutritional and medicinal properties known by indigenous people. According to [21], information about the economic value of ALV is lacking. ALVs are perceived as foods with low social status and only meant for the poor by certain communities [25, 39]. Young consumers still prefer Western-based diets which are widely promoted on media platforms and represent a higher-class status within their communities. But [36] have reported that in Kenya, consumer awareness about the nutritional benefits of ALVs has resulted in an increase in their use.

#### **8. Conclusions**

The current review has demonstrated the advantages of using ALVs as part of a plant-based diet, however, awareness about the nutritional and medicinal benefits of ALVs is still needed to change current consumer perceptions and preferences. Most of the ALVs discussed have micronutrients which can be used to address the challenge of hunger. Their sale by communities can contribute to socio-economic development [18] and address the goal of ending poverty in the sub-Saharan region and hidden hunger globally. Research is still needed to assess the bioavailability of nutritional compounds and their benefits following digestion to recommend their use in plant-based diets. The ability of the vegetables to withstand adverse climatic conditions and growth with minimal water and pesticide input was also demonstrated. This highlights the continuous availability of ALVs despite climate change challenges. The way forward would be the development of policies that advocate for and promote the use of ALVs as proposed elsewhere [12]. Although fermentation has been used as an effective method to prolong the shelf life of ALVs, sensory evaluation studies indicate consumer acceptance of fermented vegetables is minimal. This highlights the need to continuously investigate various postharvest preservation methods to protect this valuable nutritional resource for plant-based diets.

#### **Acknowledgements**

The author would like to thank the Central University of Technology, Free State, the South African National Research Foundation (NRF), and the Southern African Science Service Centre for Climate Change and Adaptive Land Management (SASSCAL) for supporting the work conducted in this study.

#### **Conflict of interest**

"The authors declare no conflict of interest."

*Nutritional and Functional Value of African Leafy Vegetables: Advantages and Limitations DOI: http://dx.doi.org/10.5772/intechopen.112972*

#### **Author details**

Ntsoaki Joyce Malebo Central University of Technology, Free State, Bloemfontein, South Africa

\*Address all correspondence to: nmalebo@cut.ac.za

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Section 2
