**6. Dietary approaches to the management of type 2 diabetes mellitus**

A diet is a combination of foods individuals or community habitually eat to exist or live, or use for therapeutic purposes. Diet is known for many years to play a key role as a risk factor for chronic diseases [7]. Conventionally, type 2 diabetes is controlled with diet alone or diet and hypoglycaemic drugs (in combination with insulin in few cases where pancreas produces

no insulin because of age). Objectives of dietary management of diabetes are to: achieve optimal blood glucose and blood lipid concentrations; provide appropriate energy for reasonable weight, prevent, delay and treat diabetes-related complications and improve health through optimal nutrition [65]. The general practice is to counsel people with diabetes on moderation of their food intake through proper food selection with incorporation of low GI foods that contain slowly digestible carbohydrates and increased consumption of dietary fibrerich foods in combination with increased physical activity. Most often, diabetics are misin‐ formed and advised to consume only those foods with low GI values. The restriction has two adverse effects: either the diabetics become too rigid with their food selection which might cause starvation and frequent hypoglycaemic attacks [66] or consume more carbohydrate per meal from the low GI diets. These precipitate poor diabetic control (hyperglycaemia). This has resulted in reduced intake or total avoidance of starchy staples and overall poor diabetes management in Nigeria with its attendant high cost of medical treatment. The types of foods/ diets eaten in Nigeria vary tremendously and depend on several factors. Climate, environment, cost and availability of foods, and religious beliefs are among the factors. There are also significant differences in eating habits between the rural and urban populations. The latter increasingly adapt to western food habits [67]. The promotion of indigenous mixed diets still remains a powerful weapon in the fight against diabetes.

leaves) at different levels of incorporation [5-15%) into single meals of subjects [70, 71, 72, 73]. These studies tend to support the American Diabetes Association (ADA) position [15] that the public should consume adequate amounts of dietary fibre from a variety of plant foods. Unfortunately, recommended dietary fibre intakes 20-35g per day for healthy adults and the aged [7], and 5g per day for children [74], respectively, are not being met. Recent studies have shown that high carbohydrate, high fibre diets have low glycaemic index and reduce blood cholesterol and triglyceride levels. This more flexible glycaemic index concept replaces the therapeutic distinction between simple versus complex carbohydrates. Quantification of bioactive compounds *in vivo* is costly and time consuming. Liu [75] reported that synergistic effects of phytochemicals in fruits and vegetables are best acquired through whole-food consumption, not from expensive dietary supplements. It is recommended that consumers should eat 400g or 5 servings of fruits and vegetables from a wide variety of fruits and

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One limitation of dietary recommendations is the problem of translating them into practical terms. This appears to be a major gap in knowledge, which should be explored to translate the accumulated scientific evidence of plant foods benefits into practical terms. FAO/WHO/UNU [76] recommended the food-based dietary guideline (FBDG) to address problem of dietary inadequacies and poor nutrient intake. This ensures supply of nutrients per 1000kcal (nutrient density) of the traditional diet as consumed relative to standard values. The concept is used to express required, desirable nutrient intake and population goals relative to energy intake. It strongly emphasizes that food-based approaches are the only sustainable strategy to improve the nutritional status of all. Its major advantages are - it is easy to adopt and imple‐ ment; emphasizes changes that promote adequate vitamins and minerals, and reduce risks of food-borne illness, obesity, diabetes, cancers and CVD. It also portrays long term effects of diets as consumed [76]. For instance, a total of 15-20g dietary fibre/1000kcal and sodium 1000mg/1000kcal are recommended. McCarty [33] proposed a dietary 'phytochemical index' as a means of improving phytochemical nutrition of clients/patients. This index is the per‐ centage of dietary calories derived from foods rich in phytochemicals. Calories derived from fruits, vegetables, legumes, whole grains, nuts, seeds, fruit/vegetable juices, soy products, wine, beer and cider- and foods compounded therefrom, would be counted in this index.

Harden et al. [77] advocated direct evaluation of GI of many meal combinations based on indigenous, more widely and frequently consumed foods. Two principal approaches were used to study the effects of increasing carbohydrate and fibre in diabetes management:

**i.** supplementation of the low fibre foods with fibre-rich sources (for instance, guar gum, flours from tallow tree, counter wood tree seeds and locust bean); and

Selective and holistic use of dietary fibre content of a mixed meal than the soluble non-starch polysaccharides (NSP) supplements has currently become of research interest. It is because the supplementation approach compromises sensory properties of indigenous food products with anti-diabetic potentials at clinically effective and acceptable levels [78]. Translation of the nutrient recommendations for specific conditions into foods for easy culinary application and

**ii.** selective use of dietary fibre–rich foods.

vegetables/day.

#### **7. Dietary recommendations for type 2 diabetes mellitus**

Nutrients are needed in certain amounts for good health. The type of food/diet people eat, in all their cultural variety, is a key universal factor that defines and affects people's health, growth and development. However, due to some environmental, genetic, physiological and metabolic factors, humans become susceptible to conditions that influence the body's homeo‐ stasis, nutrient intake and metabolism. To meet the challenges of optimizing nutrient utiliza‐ tion for specific conditions, dietary recommendations are made for various diet-related diseases. These are based on the causal factors and aim of dietary intervention in a particular disease condition. These involve consideration for the key nutrients in metabolic functions, their daily required amounts with reference to age and sex, their food sources and individual quantities of selected foods. These foods must offer desirable short or long-term health benefits without adverse effects. Dietary recommendations for prevention of diet-related chronic diseases and for people with diabetes were published by WHO [7] and American Diabetes Association [15], respectively. One major emphasis in these recommendations is that these diets should be close to normal (family) diet. In diabetes mellitus, the three energy-giving nutrients are involved. Based on this, adequate supply and intake of carbohydrate, protein and fat as well as micronutrients (vitamins and minerals) becomes an important factor to consider in diet and glycaemic control. The diet should contain 50-60% carbohydrate, 30-35% and 10-15% protein relative to the individual's total daily caloric allowance. Fruits, vegetables and spices are rich in bioactive constituents [68, 69]. Bioactive constituents (dietary fibre, phytochemicals and anti-oxidants) of plant foods are receiving attention with regard to their roles in diabetes management. Most studies used different fibre sources (legumes, cereals and leaves) at different levels of incorporation [5-15%) into single meals of subjects [70, 71, 72, 73]. These studies tend to support the American Diabetes Association (ADA) position [15] that the public should consume adequate amounts of dietary fibre from a variety of plant foods. Unfortunately, recommended dietary fibre intakes 20-35g per day for healthy adults and the aged [7], and 5g per day for children [74], respectively, are not being met. Recent studies have shown that high carbohydrate, high fibre diets have low glycaemic index and reduce blood cholesterol and triglyceride levels. This more flexible glycaemic index concept replaces the therapeutic distinction between simple versus complex carbohydrates. Quantification of bioactive compounds *in vivo* is costly and time consuming. Liu [75] reported that synergistic effects of phytochemicals in fruits and vegetables are best acquired through whole-food consumption, not from expensive dietary supplements. It is recommended that consumers should eat 400g or 5 servings of fruits and vegetables from a wide variety of fruits and vegetables/day.

One limitation of dietary recommendations is the problem of translating them into practical terms. This appears to be a major gap in knowledge, which should be explored to translate the accumulated scientific evidence of plant foods benefits into practical terms. FAO/WHO/UNU [76] recommended the food-based dietary guideline (FBDG) to address problem of dietary inadequacies and poor nutrient intake. This ensures supply of nutrients per 1000kcal (nutrient density) of the traditional diet as consumed relative to standard values. The concept is used to express required, desirable nutrient intake and population goals relative to energy intake. It strongly emphasizes that food-based approaches are the only sustainable strategy to improve the nutritional status of all. Its major advantages are - it is easy to adopt and imple‐ ment; emphasizes changes that promote adequate vitamins and minerals, and reduce risks of food-borne illness, obesity, diabetes, cancers and CVD. It also portrays long term effects of diets as consumed [76]. For instance, a total of 15-20g dietary fibre/1000kcal and sodium 1000mg/1000kcal are recommended. McCarty [33] proposed a dietary 'phytochemical index' as a means of improving phytochemical nutrition of clients/patients. This index is the per‐ centage of dietary calories derived from foods rich in phytochemicals. Calories derived from fruits, vegetables, legumes, whole grains, nuts, seeds, fruit/vegetable juices, soy products, wine, beer and cider- and foods compounded therefrom, would be counted in this index.

Harden et al. [77] advocated direct evaluation of GI of many meal combinations based on indigenous, more widely and frequently consumed foods. Two principal approaches were used to study the effects of increasing carbohydrate and fibre in diabetes management:


no insulin because of age). Objectives of dietary management of diabetes are to: achieve optimal blood glucose and blood lipid concentrations; provide appropriate energy for reasonable weight, prevent, delay and treat diabetes-related complications and improve health through optimal nutrition [65]. The general practice is to counsel people with diabetes on moderation of their food intake through proper food selection with incorporation of low GI foods that contain slowly digestible carbohydrates and increased consumption of dietary fibrerich foods in combination with increased physical activity. Most often, diabetics are misin‐ formed and advised to consume only those foods with low GI values. The restriction has two adverse effects: either the diabetics become too rigid with their food selection which might cause starvation and frequent hypoglycaemic attacks [66] or consume more carbohydrate per meal from the low GI diets. These precipitate poor diabetic control (hyperglycaemia). This has resulted in reduced intake or total avoidance of starchy staples and overall poor diabetes management in Nigeria with its attendant high cost of medical treatment. The types of foods/ diets eaten in Nigeria vary tremendously and depend on several factors. Climate, environment, cost and availability of foods, and religious beliefs are among the factors. There are also significant differences in eating habits between the rural and urban populations. The latter increasingly adapt to western food habits [67]. The promotion of indigenous mixed diets still

remains a powerful weapon in the fight against diabetes.

68 Antioxidant-Antidiabetic Agents and Human Health

**7. Dietary recommendations for type 2 diabetes mellitus**

Nutrients are needed in certain amounts for good health. The type of food/diet people eat, in all their cultural variety, is a key universal factor that defines and affects people's health, growth and development. However, due to some environmental, genetic, physiological and metabolic factors, humans become susceptible to conditions that influence the body's homeo‐ stasis, nutrient intake and metabolism. To meet the challenges of optimizing nutrient utiliza‐ tion for specific conditions, dietary recommendations are made for various diet-related diseases. These are based on the causal factors and aim of dietary intervention in a particular disease condition. These involve consideration for the key nutrients in metabolic functions, their daily required amounts with reference to age and sex, their food sources and individual quantities of selected foods. These foods must offer desirable short or long-term health benefits without adverse effects. Dietary recommendations for prevention of diet-related chronic diseases and for people with diabetes were published by WHO [7] and American Diabetes Association [15], respectively. One major emphasis in these recommendations is that these diets should be close to normal (family) diet. In diabetes mellitus, the three energy-giving nutrients are involved. Based on this, adequate supply and intake of carbohydrate, protein and fat as well as micronutrients (vitamins and minerals) becomes an important factor to consider in diet and glycaemic control. The diet should contain 50-60% carbohydrate, 30-35% and 10-15% protein relative to the individual's total daily caloric allowance. Fruits, vegetables and spices are rich in bioactive constituents [68, 69]. Bioactive constituents (dietary fibre, phytochemicals and anti-oxidants) of plant foods are receiving attention with regard to their roles in diabetes management. Most studies used different fibre sources (legumes, cereals and

Selective and holistic use of dietary fibre content of a mixed meal than the soluble non-starch polysaccharides (NSP) supplements has currently become of research interest. It is because the supplementation approach compromises sensory properties of indigenous food products with anti-diabetic potentials at clinically effective and acceptable levels [78]. Translation of the nutrient recommendations for specific conditions into foods for easy culinary application and appropriate nutrient intake is an integral part towards achieving the goals of dietary recom‐ mendations.

pathological perception of diseases and therapeutic behaviours. This gives indigenous knowledge in agriculture, medicine and health its diverse and pluralistic nature. The impli‐ cation is that success for use of any indigenous plant foods that possess antidiabetic potential when incorporated into the family diets, could offer sustainable health benefits to the com‐

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Several terms have been used to describe the therapeutic potentials of plants. Health-promot‐ ing activities, bioactive constituents, medicinal properties (often used in orthodox and traditional medicine), natural plant products and biological response modifiers are examples of such terms. All plants, especially the wild ones, are potential sources of biological active molecules. These compounds protect plants against predators and other damage but are not directly essential for growth. They are known as secondary chemical compounds or metabo‐ lites. The plant constituents useful extractable substances in their storage organs (leaves and seeds/roots) in quantities sufficient to be economically useful as raw materials for various

Some plant constituents appear to be disease specific. The plants for consideration when a hypoglycaemic property of a plant is elucidated were reported. Ivorra et al. [28] studied different compounds isolated from plants with attributable hypoglycaemic activity. They gave a broad classification as follows: polysaccharides and proteins; steroids and terpenoids; alkaloids; flavonoids and related compounds. Drewnowski and Gomez-Carneros [29] and Noor et al [23] reported phenols and polyphenols, flavonoids, isoflavones, terpenes and glucosinolates in vegetables and fruits; Thompson et al. [79] included phytate in bean flour, which reduced GI. Iwu et al. [80] found alkaloids in yam. Several studies have published similar effects with dietary fibre (non-starch polysaccharides, NSPs) [31, 73]. A new classifi‐ cation of dietary fibre (water-soluble and insoluble dietary fibre) was based on their solubility characteristics [81]. The soluble dietary fibre is highly viscous and has added viscosity as functional property in the evaluation food/diets. These NSPs lower blood glucose level by impeding glucose absorption from the gastrointestinal tract and reduce post-prandial hyper‐ glycaemia. The water-insoluble NSP are mainly obtained from structural carbohydrates (cellulose and lignin of cell walls) of starchy roots/tubers and cereals. The water-soluble NSP are obtained from storage carbohydrates (gum and hemicellulose) of legumes and as pectin from fruits and vegetables. The phytochemicals are basically sourced from fruits and vegeta‐

Widely used parameters for clinical studies in diabetes are post-prandial blood glucose, glycaemic index (GI) and glycaemic load (GL). Jenkins et al. [82] introduced the concept of GI to classify both single foods and mixed meals on the basis of their potential for increasing the blood glucose concentration. The starchy foods have high GI (>70%) compared to the low values (<50%) for vegetables, fruits, legumes. The GL is defined as the product of the amount

munity/consumers of such plant foods.

**9. Bioactive constituents and their effects on diabetes**

scientific technological and commercial applications [3].

bles.
