**7. Role of protein in human body**

Protein is involved in almost all the body functions taking place such as development of muscle, bone, skin, hair, etc. It makes up the enzymes that trigger many chemical reactions within the body, e.g., the hemoglobin is responsible for carrying oxygen in the blood. Protein plays an important role in growth and muscle building. Protein requirements increase during illness, pregnancy, breastfeeding, and after surgery or an injury. Enzymes are also protein in nature that control metabolic processes within and outside the cell. These enzymes' functions are critical during the process of digestion, blood clotting, muscle contraction, and energy production [37].

Some hormones are also made up of proteins; these are chemical messengers that conduct communication between cells, tissues, and organs. Some hormones are insulin, glucagon, human growth hormone, antidiuretic hormone, adrenocorticotropic hormone. Protein is helpful in maintaining the acid and base balance in body fluids including blood, gastric juice, etc. Proteins required to regulate body fluids as albumin and globulin are present in blood and are helpful to maintain body fluid by attracting and retaining the water. Protein is helpful in the formation of immunoglobulins or antibodies; these are necessary to fight against infections and play an important role in immune system. It also helpful in transporting nutrients, i.e., vitamins, minerals, blood sugars, oxygen, and cholesterol into cells, out of cells, and within cells. Proteins also play an important role in storing nutrients as ferritin is a form of protein that stores iron. Protein provides energy to body in the same amount as carbohydrates 4 g/kcal [38].

#### **8. Outcomes of protein deficiency**

Protein becomes deficit when intake of protein does not meet body requirement. According to an estimation, one billion people suffer from inadequate protein intake worldwide, protein deficiency is especially severe in Central Africa and South Asia, where up to 30% of children could not get sufficient amount of protein from their diet. Certain people in the developed countries are also at risk, who follow an imbalanced diet, as well as older people and hospitalized patients. Low protein consumption may result in compositional changes within the body that develop over a long period of time, such as muscle wasting. Kwashiorkor is the most severe form of protein deficiency. It often occurs in children in developing nations because of famine and lack of balanced diets. Protein deficiency can affect almost all aspects of body function [15].

Edema, characterized by swollen and puffy skin, is a classic symptom of kwashiorkor. Scientists believe it is caused by low amounts of human serum albumin and globulin, which is the most abundant protein in the liquid part of blood or blood plasma. When levels of albumin and globulin decrease in body, they are no longer able to regulate blood in blood vessels, and then fluid starts to build in spaces of cells, edema and swelling occur specially in stomach region [39].

Another common symptom of kwashiorkor is a fatty liver or fat accumulation in liver cells. Main cause of this is unknown, but some studies suggest that an impaired synthesis of fat-transporting proteins, known as lipoproteins, may contribute to the condition. Protein deficiency often leaves its mark on the skin, hair, and nails, which are largely made of protein as keratin protein present in hair. For instance, kwashiorkor in children is distinguished by flaky or splitting skin, redness, and patches of depigmented skin. Hair thinning, faded hair color, hair loss (alopecia), and brittle nails are also common symptoms [40].

Muscles are said to be body's largest reservoir of protein. When dietary protein is in short supply, the body tends to take protein from skeletal muscles to preserve more important tissues and perform body functions. Over the time this lack of protein leads to muscle wasting. Even moderate protein insufficiency may cause muscle wasting, especially in elderly people. Bones gives support and shape to body, are also at risk when there is protein deficiency, and risk of fractures increases. One study in postmenopausal women found that a higher protein intake was associated with a lower risk of hip fractures. The highest intake of protein is linked to a 69% reduced risk of fractures [41].

*Pulses: A Potential Source of Valuable Protein for Human Diet DOI: http://dx.doi.org/10.5772/intechopen.99980*

Besides maintaining muscle and bone mass, protein is essential for body growth. Thus, growing age deficiency or insufficiency is especially harmful to children who require a steady supply of protein. In fact, stunting is the most common sign of childhood malnutrition. In 2013, an estimated 161 million children suffered from stunted growth that reaches up to 38.9 million during 2020. Stunted growth is also one of the main characteristics of kwashiorkor in children. Similarly the rate of wasting rises from 149.2 million to 203.6 million during this decade. A protein deficiency can also affect the immune system. Impaired immune functionality may increase the severity of infections. For instance, one study in mice showed that following a diet consisting of only 2% protein was associated with a more severe influenza infection, compared with a diet that provides 18% protein [42].

## **9. Role of pulses/legumes protein in human health**

Pulses can play an important role in food systems to provide global food security and fulfill the nutritional needs in future. Food systems fail to provide safe, sufficient, nutritious food to all due to urbanization, climate change, and increase in population [43]. Leguminous family is highly appreciated as it is a cheap and safe source of nutrients especially protein. Compared with different maize, that is a staple in different regions of world, pulses are a better and effective source of protein and are rich in micronutrients such as iron, zinc, thiamin, folate, and niacin. Nutrient concentration varies in different varieties, locations, and between grains. Human nutrient consumption and status clearly depend on the bioavailability of nutrients. Furthermore, pulses are a good source of essential amino acids especially in lysine (∼64 mg/g of protein) and threonine (∼38 mg/g of protein), which are complementary to most staple foods, helpful to improve the quality of protein of diet. Pulses offer potential health benefits where future demand of nutritious and cheap food commodities is increasing because of lack of resources and undernutrition [7].

Protein requirements is not same for everyone; it depends on many factors including body weight, muscle mass, age, and physical activity. The recommended daily allowance of protein is 0.4 g per pound of body weight and 0.8 g per kg of body weight. Athletes required a greater amount of protein ranging from 0.5 to 0.6 g per pound of body weight (1.2–1.4 g per kg), required for muscle maintenance and training recovery. Pulses contain 21–25% protein and provide double amount as compared with cereals [44].

Protein is a most satiating macronutrient than fat and carbohydrates, and it is present in a high amount in pulses. Protein elicits the secretion of satiety-related hormones in the small intestine such as peptide YY, Glucagon such as peptide-1. Fiber and protein both are helpful to control satiety; pulses are rich in both fiber and protein and ideal to reduce caloric intake and managing obesity [45].

Pulses are recommended by Canadian and American government agencies as part of a healthy diet. Both Canada's Food Guide (CFG) and the USDA MyPlate nutrition guides place pulses in the meat and alternative group. Animal protein is expensive and not acceptable for many people due to their beliefs and lifestyle. Pulse protein could be a great choice for vegetarian people and meet their essential requirements of amino acids for physiological processes and growth of children. Pulses supply a good amount of protein when consumed with cereals [46].

#### **10. Protein digestibility of pulse-based diet**

Protein digestibility can be defined as the percentage of protein or AA intake, absorbed by the digestive tract. It can also predict the estimated individual AA

bioavailability [47, 48]. When protein-containing food is consumed, digestion begins from the stomach, and it triggers the release of the hydrochloric acid in the stomach by the partial cells of gastrointestinal mucosa of the gastrointestinal tract. Released acid activates the pepsinogen and converts it into active form, i.e., pepsin. This pepsin can break down the polypeptides into di- and tripeptides, which are ultimately broken down into amino acids; within the duodenum amino acids travel to the liver through hepatic portal vein and undergo de-amination. Amine groups are cleaved to form urea. The amino acids are simultaneously converted into non-essential amino acids or carbohydrate and fats or catabolized directly to energy. Since protein cannot be stored within the body, metabolism of amino acids is completed within few hours. If neither of these actions occurs, then it is released from the body in the form of urine or urea nitrogen contents (**Figure 1**) [49, 50].

When we come to digestibility of pulse-based diet, it is evident that some type of anti-nutritional factors inhibit the digestibility and availability of protein to the body. These may be some types of protein inhibitor components such as trypsin and chymotrypsin inhibitors that arrest the functionality of proteolysis. Trypsin is a digestive enzyme, and the presence of this inhibitor interferes with normal protein digestion in humans. Presence of less digestible protein fractions, high levels of insoluble fiber, and high concentrations of anti-nutritional factors lowers the digestibility of protein. However, processing, cooking, and germination improve the digestibility of pulses. The preparation involves soaking, autoclaving, roasting, fermentation, and germination to reduce anti-nutritional factors (phytic acid, tannins, and polyphenols), which inhibit mineral absorption and protein bioavailability [50–52].

Starch present in pulse grains provides certain health benefits due to its high amylose content. It promotes the formation of resistant starch that cannot be hydrolyzed during digestion. Dietary fiber remains undigested in the small intestine; afterward, it is fermented by the microbiota in the colon that is helpful in controlling weight management, diabetes, and has cholesterol-lowering effect. Fruits and vegetables rich in promoter substances (ascorbate and beta-carotene) for mineral absorption should be taken to enhance micronutrient content and bioavailability. When processed, cooked, or heat-treated, the process of protein digestion by gastrointestinal enzymes as the inhibitory effect on proteolytic enzymes is inactivated [30]. Cooking or heat treatment increases the enzyme activity 2–3 times, chelating activity was also found to be increased in different legumes by cooking. Overall, the

**Figure 1.** *Catabolism of protein.*

*Pulses: A Potential Source of Valuable Protein for Human Diet DOI: http://dx.doi.org/10.5772/intechopen.99980*

total antioxidant capacity values denoted the increased electron donating capacity of the legume seed proteins after digestion with GI enzymes, which could thus act as better radical chain terminators or free-radical stabilizers, when legumes and pulses are treated with heat application [53]. Overall the nutritional value and bioavailability of nutrients, proteins, minerals, phenolic or antioxidant capacity, are increased or improved by processing methods applied to grains as compared when consumed in raw form.
