The Role of Pulses in Human Nutrition : A Review

Pulses belong to the family leguminosae (COPR, 1981). The family leguminosae is made up of many species which are cultivated all over the world (Rubatzky and Yamaguchi, 1997). Legumes have a wide range of usage, some are used as fodder or green manure, some are used as silage, while others are extracted for their oil, notably soyabean and groundnut (COPR, 1981). Such oil contributes a great deal to the energy intake of people all over the world. Majority of legumes are grown for their green pods, green seeds, or dried seeds (COPR, 1981). The term pulses cover all those grown for their dried seeds (COPR, 1981). Pulses have a variety of functions. The use of pulses range from their forming a staple diet to their being used as condiments, milk, cheese and snacks (Reddy et al., 1986; Uzogara and Ofuya, 1992). They play a very important role in human nutrition. The present paper reviews the work that has been done on the nutritional value of pulses.

Pulses belong to the family leguminosae (COPR, 1981).The family leguminosae is made up of many species which are cultivated all over the world (Rubatzky and Yamaguchi, 1997).Legumes have a wide range of usage, some are used as fodder or green manure, some are used as silage, while others are extracted for their oil, notably soyabean and groundnut (COPR, 1981).Such oil contributes a great deal to the energy intake of people all over the world.Majority of legumes are grown for their green pods, green seeds, or dried seeds (COPR, 1981).The term pulses cover all those grown for their dried seeds (COPR, 1981).Pulses have a variety of functions.The use of pulses range from their forming a staple diet to their being used as condiments, milk, cheese and snacks (Reddy et al., 1986;Uzogara and Ofuya, 1992).They play a very important role in human nutrition.The present paper reviews the work that has been done on the nutritional value of pulses.
Production: Pulses are grown all over the world (Reddy et al., 1986).Production as per continent is shown in the table below.FAO Year Book (1975& 1986) Asia is the largest producer of the pulses listed above, followed by the USSR, where most of the pulses produced are in the form of dry Peas (Pisum sativum).The next largest producing continent for all pulses is Africa and the types of beans majorly produced are dry beans (Phaseolus vulgaris), broad beans (Vicia faba) and cowpeas (Vigna unguiculata).
The continent that produces next to Africa is Europe, where most of the pulses produced are dry Peas (Pisum sativum).The least producing continents are North America, Central and South America.In these continents the dry beans (Phaseolus vulgaris) constitutes the pulse produced most.

Consumption of Pulses:
Pulses are consumed all over the world.Consumption is higher in those parts of the world, where animal proteins are scarce and expensive for example, South East Asia and Africa (COPR, 1981).In this part of the world, they provide a large proportion of the protein required for adults and children.About 20% of the protein presently available to man, come from pulses in the developing countries (Reddy et al., 1986).

The nutritional value of pulses:
The nutritional importance of pulses are numerous, they can be a valuable source of energy.The energy content of most pulses have been found to be between 300 and 540 Kcal / 100g (Table 2).Energy is required for all metabolic processes.The energy of Pulses come from the nutrient supply of protein, fat and carbohydrate.Gopalan et al (1980) The carbohydrate supply: The carbohydrate content of pulses is high (Table 3) (Reddy et al., 1985;Oke et al., 1995).The high carbohydrate content contributes a great deal to the energy supply of pulses.A large percentage of pulses occurs as starch (Table 3), about 1.8 -18% occurs as oligossacharide while 4.3 -25% occurs as dietary fibre (Table 4).Although the oligossacharides, which are made up of raffinose, stachyose, verbascose, cause gas production in man, they are presently believed to have some beneficial effects.They can shorten transit time and promote the growth of bifido bacteria in man.
Infact researchers in Japan have actually suggested that oligossacharides from soyabeans could be used as substitute for common table sugar.They are also hypothesized to improve longevity and reduce colon cancer risk (Hayakawa et al., 1990;Koo and Rao, 1991).The high dietary fibre content of pulses (Table 4), are postulated to have some important physiological effects, such as reducing the transit time in the mammalian gut (Sathe et al., 1984).This would help to relieve gastrointestinal conditions such as constipation and diverticular disease.It is also capable of lowering the blood cholesterol level due to its ability to bind with cholesterol in the human gut (Burkitt and Trowell, 1985).This feature is being suspected as being capable of reducing colonic cancer in man (Davis and Stewart, 1987;Hangen and Bennink, 2002).Pulses also have low glyceamic indices (Hatford, 1985;Björek et al., 2000), which makes them valuable foods for diabetics.The cotyledon of legumes like locust bean and guar (guar gum) reduces postprandial glucose and insulin concentrations in man (Fairchild et al., 1996;Gatenby, 1991;Feldman et al., 1995).

PROTEIN SUPPLY
Pulses have a high protein content (Table 5), the value is about twice that in cereal and several times that in root tuber (FAO, 1968), so they can help to improve the protein intake of meals in which cereals and root tubers in combination with pulses are eaten (Kushwah et al., 2002).Pulse when eaten with cereals, can also help to increase the protein quality of the meal (Table 6).In man, protein helps in the repair of body tissue, synthesis of enzymes and hormones and also in the supply of energy.In children, the consumption of pulses should be encouraged, particularly where animal protein is scarce and expensive, as this would help to furnish the child with the necessary amino acids required for growth.

Table 3. Starch and Total Carbohydrate Content of Pulses
Source: Reddy et al. (1985); Frank-Peterside, Dosumu, and Njoku (2002); Ofuya (2002); Oke, Tewe, and Fetuga (1995).Bressani (1972) FAT SUPPLY: The fat content of pulse varies in different species.Most species contain about 1% fat, while groundnut and soyabean, have very high fat content, about 30% for soyabean and 49% for peanut (FAO, 1968).The fat content besides contributing to the energy needs, provides the needed essential fatty acids for man.A pulse like soyabean, contains linolenic acid, which is an omega-3-fatty acid.This fatty acid is currently being studied for its ability to reduce the risk of heart disease and cancer.

MICRONUTRIENT SUPPLY VITAMIN SUPPLY:
The vitamins present in appreciably quantities in pulses are thiamin, riboflavin, pyridoxine and folic acid; vitamin E and K are also found in pulses.The B-vitamins act as coenzymes in biological processes Vitamin E is known to play a role as an antioxidant inhibiting the oxidation of vitamin A in the GIT and of polyunsaturates in the tissues.It is also believed to maintain the stability of cell membranes (Davies and Stewart, 1987).Vitamin K functions primarily in the liver where it is necessary for the formation of blood clothing factors.

Conclusion:
Thus far, the many important functions of pulses have been highlighted.Their consumption should be encouraged in both adults and children.Because of their high dietary fibre content, I will advice more usage among the affluents who can afford lots of animal protein.Their use should also be encouraged among malnourished children because of their high protein content.The use of pulses as components of weaning foods in combination with cereals is also recommended, as this would give cheaper cereals with more complete protein.Finally, the use of oil from pulses should be encouraged because of the high polyunsaturated fatty acid content.Polyunsaturated fatty acids are suspected of being capable of reducing the risk of heart diseases.

Table 1
Production of Pulses by Continent in 10 3 Mt*

Table 2 .
The Energy Content Of Some Pulses Commonly Consumed By Man

Table 4 .
Dietary Fibre Content of Pulses (Per 100g of Whole Mature Seeds)

Table 5 .
Protein Content Of Pulses

Table 6
Protein Quality of Cereal Grain and of Cereal Grain / Bean Diets Fed at Equal Levels of Dietary Protein