NUTRITIONAL AND HEALTH IMPLICATIONS OF LEGUMESHTML Full Text
NUTRITIONAL AND HEALTH IMPLICATIONS OF LEGUMES
Mebrahtom Gebrelibanos*, Dinka Tesfaye, Y. Raghavendra and Biruk Sintayeyu
Course and Research Unit of Pharmacognosy, Department of Pharmacy, College of Health Sciences, Mekelle University, Mekelle, Ethiopia
ABSTRACT: Legumes are plants in the family Fabaceae characterized by seeds in pods that are often ediblethough sometimes poisonous. The nutrient content (protein, carbohydrate and micronutrients) of legumes contribute to address under-nutrition, especially protein-calorie malnutrition among children and nursing mothers in developing countries where supplementing cereal-based diets with legumes is suggested as one of the best solutions to protein calorie malnutrition. Anti-nutritional factors, in legumes, may limit their biological value and acceptance as a regular food item, yet they are readily removable and recent research has shown potential health benefits of some of these compounds; and hence, manipulation of processing conditions may be required to remove or reduce only those unwanted components. Moreover, legumes play a role in prevention, improvement and/or treatment of disease conditions such as, diabetes mellitus, cardiovascular diseases, cancer diseases (e.g breast and prostate cancers) and lowers blood cholesterol level. Most of these disease conditions are associated with over-nutrition and obesity and are considered as diseases of the rich. It is, therefore, claimed that including legumes in a health-promoting diet is important in meeting the major dietary recommendations to improve the nutritional status of undernourished as well as over-nourished individuals, and to reduce risk of chronic diseases such as cardiovascular disease, diabetes mellitus and cancer. In this review, some of the scientific viewpoints that attempt to justify the nutritional contributions, anti-nutritional considerations and health implications of legumes are discussed.
Legumes, Nutrition, Anti-Nutritional Factors, Health Benefits
INTRODUCTION: A legume is a plant in the family Fabaceae (or Leguminosae), or a fruit of these specific plants,characterized by seeds borne in pods 1 and often edible, though sometimes quite poisonous 2.
Members of the family are important food sources; and food legumes are those species of the legume family that are consumed by human beings or domestic animals commonly as dry seeds, i.e. the grain legumes 3.They include peas, beans, lentils, peanuts, and other podded plants that are used as food 4.
Grain legumes are commonly subdivided into pulses and oilseeds 5. Pulses are distinguished from oil seeds by their low fat content 3. They are those grain legumes, which, in addition to protein, store high levels of carbohydrate and low amounts of lipid in their dry seeds, and leguminous oilseeds are those which boast higher lipid, but lower carbohydrate levels than pulses. Soybean (Glycine max) and peanut (groundnut, Arachis hypogaea) are typically categorized as oilseeds while common beans (Phaseolus vulgaris) and cowpea (Vigna unguiculata) are considered pulses 5.
The oil seeds are cultivated primarily for their protein and oil content, and the grain legumes as a protein source 6. The terms “legumes” and “pulses” are used interchangeably because all pulses are considered legumes but not all legumes are considered pulses.The term “pulse”, as used by the Food and Agriculture Organization (FAO), is exclusively for crops harvested solely for the dry seed of leguminous plants. This excludes oil seeds and also green beans and green peas which are consumed and considered as vegetables 3.
History and ecological importance: Generally, legumes are well known crops with long history of utilization 7, which have been cultivated for thousands of years 4. Their consumption dated back to as far as 5500 BC and they are thought to be one of the first crops cultivated by man 8. They have played an important role in the traditional diets of many regions throughout the world 4 and their value has long been appreciated in many countries 9. In addition to their food value, legumes are important in cropping systems because of their ability to fix atmospheric nitrogen and increase the overall fertility of soil, reducing the need for expensive nitrogenous fertilizers.
The dominant food legumes of any region may vary from country to country or even from region to region, but most of them can be grown under a reasonably wide range of ecological conditions and many legumes can be grown reasonably well on poor soils even without the application of fertilizers 3.
Legumes are well adapted to adverse environmental conditions and highly resistant to disease and pests 10. They are widely grown in semi-arid regions while cereals require more water and intensive cultivation11. Historically, legumes have complemented cereals in both human diets and production systems, especially in efficient use of land and water resources and sustainability of agriculture systems globally 12.
Most legumes that are used for foods are multipurpose plants, serving for animal forage as well as soil improvement due to their ability to fix atmospheric nitrogen 13. Nowadays, in addition to their nutritional, agricultural and ecological significance, legumes are of great importance because of their numerous health benefits.
Generally, despite numerous advantages (improve soil fertility, serve as food and feed, provide cheaper protein source and health promoting components), legumeshave certain limitations such as their deficiency of sulfur amino acids, poor digestibility and the presence of antinutritional factors although these limitations are not far from control as there exist recommended manipulations for their optimization.
Objective: The main objective of this review is to discuss on some of the scientific arguments about the nutritional contributions, anti-nutritional considerations and their suggested options of minimization as well as health implications of legumes.
Nutritional role of Legumes: Legumes constitute a part of the diet of nearly all humans 13 andtheir nutrient content (protein, carbohydrate and micronutrients) contribute to address under-nutrition 14. They contain complex carbohydrates (oligo-saccharides, dietary fibers and resistant starch- i.e. starch that escapes digestion in the small intestine and may ferment in the large intestine), protein with a good amino acid profile (high lysine), important vitamins (B vitamins, folates, ascorbic acid and tocopherols), minerals as well as antioxidants, polyphenols and numerous other phytochemicals endowed with useful biological activities 3, 14-17.
They are good sources of water-soluble vitamins, especially thiamine (Vitamin B1), riboflavin (Vitamin B2), niacin (Vitamin B3), pyridoxine(Vitamin B6) and folate, but poor sources of fat-soluble vitamins and vitamin C. They are low in sodium but are excellent sources of other minerals, including calcium, copper, iron, magnesium, phosphorus, potassium and zinc14, 18, 19. They have desirable characteristic such as low fat (except oilseeds), high concentration of polyunsaturated fatty acids and a long shelf life 20, 21. The predominant fatty acid is linoleic acid, although they also contain α-linolenic acid14.
Thus, legumes contain many nutritionally important and health-promoting components responsible for addressing under-nutrition and promotion of health.
Malnutrition is currently widespread in many areas of the world; and the most serious one is protein-calorie malnutrition (PCM). PCM is a widespread problem throughout the world, especially among children in the developing countries; and has both health and economic consequences. It is a major nutritional syndrome affecting more than 170 million preschool children and nursing mothers in developing Afro-Asian countries where provision of adequate proteins of animal origin is difficult and expensive. Legumes are the major contributors of protein and calories in Afro-Asian diets for economic and cultural reasons 22, 23.
The high cost and limited supply of animal proteins have necessitated contemporary research efforts geared towards the study of food properties and potential utilization of protein from locally available food crops, especially from under-utilized or relatively neglected high protein oilseeds and legumes 23. As the lower income group of the population is particularly vulnerable, it is suggested that attention must be given to easily available, accessible, cheap but nutritious plant protein sources (especially legumes – because among plants, legumes are considered the major source of dietary proteins) to improve the nutritional status of the low-income groups of the population22,23.
Legumes (poor man’s meat) play an important role in human nutrition since they are rich and economical sources of good quality protein, calories, certain minerals and vitamins, and fibre 14, 22, 24. They are inexpensive, nutrient dense sources of plant protein that can be substituted for dietary animal protein 25. However, proteins in legumes are higher in nonessential amino acids compared with proteins from animal foods 26; and their nutritive value has been known to be low because of their deficiency of sulfur amino acids, poor digestibility and the presence of antinutritional factors 23, 27.
Yet, it is suggested that sulfur amino acidsdeficiency can be solved by complementing legume with cereals 5; and food processing can improve the nutritional quality and increases the bioavailability of nutrients, by inactivating antinutritional factors 11, 28.
Thus, legumes, with the exception of soybeans, are not a complete protein like meat; however, when paired with grains or another complementary food, they provide a complete source of amino acids 19.
In developing countries, legumes complement the lack of proteins from cereals, roots and tubers 21. Their most vital role is that of supplying most of the protein in regions of high population density and in balancing the deficiencies of cereal protein 13.Legumes and cereals are considered ideal dietary partners because the amino acids making up their proteins are very good complements 5.
Cereal proteins are deficient in certain essential amino acids, particularly lysine. On the other hand, legumes have been reported to contain adequate amounts of lysine, but are deficient in sulfur-containing amino acids (methionine, cystine and cysteine). Therefore, intentional combination of cereals and legumes at meals offers cheap, compared to meat, plant-based diets with balanced amino acid composition 5, 11, 22.
Accordingly, supplementing cereal-based diets with legumes improves overall nutritional status and is one of the best solutions to protein calorie malnutrition in the developing countries 11.
Anti-nutritional factors: The use of legume seeds in food and feed is usually limited because of their deficiency of sulfur-containing amino acids, low protein digestibility and the presence of several anti-nutritional components. The anti-nutritional factors include flatulence causing raffinose family oligosaccharides (α-galactosides), phytates, phenolics, tannins, cyanogens, enzyme (trypsin, chymotrypsin and α-amylase) inhibitors and lectins (phytohemagglutinins) 5, 21, 23, 24, 27, 29, 30.
Anti-nutritional factors impede the digestion and absorption of some interesting components (e.g. proteins, vitamins), or, in some cases, they are simply toxic or cause undesirable physiological side effects (e.g. flatulence) 24. Although only a few legumes may contain all these anti nutritive factors, many contain a few of them. Tannins and cyanogens are the two anti-nutritional factors that are present almost in all legumes 30. The anti-nutritional factors can generally be categorized as proteinaceous and nonproteinaceous compounds 5.
- Proteinaceous anti-nutritional factors: Legume seeds, in addition to nutritional proteins, contain a number of other abundant proteins which may vary in types and amounts among the legume seeds. Some of them are biologically active proteins, which for years have been referred to as anti-nutritional compounds. These groups of proteins include lectins, proteases and amylase inhibitors. The proteinase and α-amylase inhibitors are monomeric seed proteins 31; and lectins are proteins that bind to carbohydrates or to molecules containing carbohydrates 5.
Lectins (or phytohemagglutinins), are present, paralleling the distribution of protease inhibitors, in theseed of a number of legume species that are consumedby humans 32, 33. Protease inhibitors often inhibit the digestive enzyme trypsin, but may act more broadly by inhibiting chymotrypsin and other serine proteases 5. They can retard growth by interfering with dietary protein digestion; and as a mechanism to adapt to this situation, the secretory activity of the pancreas can be stimulated and its size enlarged leading to an overall physiological effect of impaired growth and enlarged pancreas 33.
Young humans and other animals are more susceptible to the effects of protease inhibitors than adults and are primary concern as these can impair nutrient utilization and reduce growth rates in the young groups. Lectins differ in the severity of their impact (toxic, only growth inhibitory or essentially nontoxic) 5. Their antinutritional effects lies in the fact that dietary lectins strongly resist proteolytic degradation in the gut and bind to surface receptors 5, 32 on the cells lining the small intestines and interfere with the absorption of nutrients; the result is a failure in growth and eventual death 33.
Options for minimization of problems: Fortunately,in many cases, protease inhibitors and lectins are heat labile and rendered innocuous by usual methods of cooking. Both are heat-labile andcan be effectively eliminated or inactivated, essentially under the same conditions, by the heattreatment involved in domestic cooking and commercialprocessing 5, 33.
- Non-proteinaceous anti-nutritional factors: Non-proteinaceous compounds include phytic acid, α-galactosides, phenolics and tannins, cyanogens and toxic amino acids 5, 21, 30, 32, 33.
- Raffinose family oligosaccharides (RFOs): RFOs of legumes are synthesized by sequential addition of galactose units to sucrose 34 and are α-galactosyl derivates of sucrose 29. These α-galactosides or oligosaccharides are a common carbohydrate present in the seed of grain legumes 32. Raffinose is the first member of the series. Verbascose, stachyose and ajugose are the next higher RFOs 34. RFOs of legumes produce flatulence. Humans do not have the enzyme α-galactosidase to cleave the α-galactosyl linkage and the intact oligosaccharide is not absorbed by the digestive tract. These oligosaccharides accumulate in the large intestine where the α-galactosidase containing intestinal bacteria degrade them and subsequent anaerobic fermentation results in production of H2, CO2 and traces of CH4. These gases cause abdominal discomfort due to a flatus effect and sometimes result in diarrhea 29.
Options for minimization of problems: Traditional methods of processing grain legumes prior to their consumption significantly reduced the level of oligosaccharides 32; and the flatulence side effect of legume oligosaccharides can be minimized in different ways such as processing, plant breeding, incorporation of microbial or plant α-galactosidase, or by changing the water in which beans are boiled one or more times 14, 29.
- Tannins: Many plant species contain tannins. However, the seed of a number of legume species contain appreciable quantities of tannins 32, 33. Tannins are present in almost all legumes predominantly. They are complex group of phenolic compounds which are astringent in taste that precipitate proteins. They have major impact on both human and animal nutrition because of their ability to form complexes with molecules like carbohydrates, proteins, poly-saccharides, enzymes involved in protein and carbohydrate digestion 30. The anti-nutritional impact of tannins on digestion and metabolism is not fully understood, but the major effect is to interfere with the digestibility of dietary protein 5, 33. This may be due to the binding of the tannins to the protein to form substrates that are resistant to digestive enzymes (indigestible complexes) or to a direct binding to these enzymes themselves 32, 33. They can irritate the gut lining and stimulate the secretion of mucus. This increases endogenous protein secretion and therefore increases protein demand. They also form complexes with divalent metals and reduce mineral absorption. A common feature of diets high in tannin is weight loss 32.
Options for minimization of problems: Since tannins are located primarily in the seed coat of dry seeds, the physical removal of the seed coat by dehulling or milling markedly reduces the tannin content with a resultant improvement in the nutritional quality of the protein. Soaking in water or salt solution prior to household cooking also causes a significant reduction in tannin, provided the cooking broth is discarded 32,33. Soaking may help leach out some tannins, but heat treatment will not reduce the impact of that remaining in the seeds 5.
- Cyanogens: Relatively high level can be found in grain legumes (pluses). Cyanide in trace amounts is fairly wide spread in the form of glycosides (cyanogens). These glycosides are non-toxic in the intact tissue but when later are damaged or begin to decay, a hydrolytic enzyme is released liberating hydrogen cyanide. The hydrogen cyanide is rapidly detoxified in the liver by conversion to thiocyanate. Excess cyanide ion can quickly produce anoxia of the central nervous system through inactivating the cytochrome oxidase system and death can result in few seconds 30.
Options for minimization of problems: One method of reducing the problem is via plant breeding 32. A further reduction in toxicity is achieved by the application of heat (boiling, roasting, or sun drying), which serves to inactivate hydrolytic enzyme and to volatilize any hydrogen cyanide that may have been produced 33.
- Phytate: Phytic acid or its salt, phytate, is inositolcombined with six phosphate groups and is acommon constituent of most plants and legumes. Its antinutritionaleffect lies in the fact that it forms a chelatewith metal ions such as calcium, magnesium, zinc,and iron to form poorly soluble compounds that arenot readily absorbed from the intestine, thus interferingwith the bioavailability of these essentialminerals.
Options for minimization of problems: The ability of phytate to bind metal ions islost when the phosphate groups are removed by hydrolysisthrough the action of phytase. Heat alone isrelatively ineffective in reducing the phytate contentof plant materials, but the phytate content can be reduced by taking advantage of the endogenous phytase that accompanies the phytate in separate compartments of the plant tissue. Traditional fermented dishes have reduced levels of phytate, presumably due to the action of phytase produced by various molds, bacteria or yeasts involved in the fermentation. The germination of mature seeds of various legumes results in a great increase in phytase activity with a concomitant reduction in phytate 33.
- Toxic Amino Acids: In the legume family, there are two toxic non-protein amino acids that have a major negative effect on animals or humans that consume them: mimosine and 3-N-oxalyl-L-2, 3-diaminopropanoic acid (ODPA) 32, 33, 5. Non-protein amino acids are common within the legume family, which are often highly toxic, and are responsible for several serious human toxicoses, among the best known of which is lathyrism, a nonprogressive motor neuron disease associated with high consumption of grass peas (Lathyrus sativus).
Consumption of large amounts of Lathyrus seed in the diet often occurs at times of food shortages as a result of drought. Grass peas, which are ideally suited to arid regions such as Ethiopia and the Indian subcontinent, contain high levels of ODPA in their seeds, and this compound is responsible for the neurological symptoms and also for deleterious effects on bone formation, particularly in children. There is also some evidence that the response to Lathyrus consumption may be sex linked, as it seems to have a major effect on young Males 32, 35. The tropical legume tree, Leucaena leucocephala, contains the amino acid mimosine.
The full chemical name of mimosine is β-[1-(3-hydroxy-4-pyridone)]-α-amino propionic acid.L. leucephela is used primarilyas a forage crop for feeding livestock, but itsuse is limited by the fact that it contains mimosine. Leucaena seed is usually only used to a limited extent in human diets. One of major effects of mimosine is to stop hair growth; and it has an adverse effect on the growth of ruminantsbecause bacteria can convert mimosine to 3, 4-dihydroxypyridine which acts as agoitrogenic agent 32, 33.
Options for minimization of problems: As with many other legume species that contain antinutritional factors, the toxic amino acids can be removed by traditional processing methods such as soaking, boiling, and fermentation 32. Over 90% of the ODPA toxin can be eliminated by the simple expedient of soaking the seeds overnight in an excess of water followed by steaming, roasting, or sun drying 33. Although low-ODPA lines of grass pea have been developed through traditional breeding and selection that appear suitable as supplementary material for animal feeds, removal of the neurotoxin from the seed by transgenic approaches is yet to be reported 35.
- Summary points on anti-nutritional factors: Generally, anti-nutritional factors can decrease palatability, diminish protein digestibility and mineral bioavailability 21; and thereby limit the biological value and acceptance of legumes or pulses as a regular food item 29. Thus, they have to be appropriately treated prior consumption 21. It is suggested that legumes are not eaten raw, but processed in a way that inactivates the anti-nutritional factors. Traditional food preparation techniques result in reduction or elimination of metabolic impediments by anti-nutritional factors 5; and food processing not only improves flavor and palatability of foods but also increases the bioavailability of nutrients, by inactivating antinutritional factors 28.
- Health Implications of Legumes: The health benefits of legumes have been known for millennia14. The observation that diets low in meat and high in cereals and legumes are beneficial for health has recently become a topic of scientific interest, but was noted at least as far back as the Old Testament 36. People have grown and used legumes as a dietary staple since early biblical times, long before modern nutrition researchers endorsed their significant health virtues. Nowadays, it is claimed that including legumes in a health-promoting diet is important in meeting the major dietary recommendations to improve the nutritional status of undernourished as well as over nourished individuals, and to reduce risk for chronic diseases such as cardiovascular disease, diabetes mellitus and cancer 14.
As noted above, owing to their rich nutrient content, supplementing cereal-based diets with legumes is suggested as one of the best solutions to protein calorie malnutrition in the developing countries 11, 22-24, which reflect the role of legumes to improve the nutritional status of undernourished individuals. On the other hand, over-nutrition and obesity are associated with increased risk of non-communicable diseases such as diabetes, ischaemic heart disease, stroke, and hypertension 37, 38; and legumes play a role in prevention, improvement and/or treatment of such disease conditions 21, 28, 36, 39. Hence, once regarded in Western countries as food for poor people, legumes continue to gain recognition for their importance in health and have now become a ‘health food’ for affluent people14.
Obesity, cardiovascular disease, diabetes, and cancer have recently become major threats to human health in many nations at least in part due to changes in eating and drinking habits. Although the etiology is multi-factorial, diet has been identified as the most important environmental risk factor for development of these diseases 15.
Experimental, epidemiological and clinical studies show correlations between the consumption of food legumes and decreasing incidence of several chronic disease conditions such as type 2 diabetes mellitus, cardiovascular disease, cancer diseases (e.g breast and prostate cancers), overweight & obesity, osteoporosis, hypertension, gastrointestinal disorders; and results in lowering of low density lipoprotein cholesterol and elevated high density lipoprotein cholesterol levels. Legumes play a role in prevention, improvement and/or treatment of these disease conditions 17, 21, 28, 36, 39.
Below are some of the scientific arguments that attempt to explain the role of legumes in managing certain diseases.
- Type 2 Diabetes Millitus: Legumes may offer benefits in the prevention of diabetes and in the clinical management of established diabetes. They reduce the risk of developing diabetes because of their high-fibre, low-fat content and low glycaemic indices. They are slowly digested and produce uniformly low blood glucose response that result in low glycaemic and insulin responses3, 9, 14, 21.Glycemic index is a measure of the potential for carbohydrates in different foods to raise blood glucose levels. Generally, foods with high glycemic index (such as white rice or potatoes) cause rapid rise in blood glucose levels, which result in greater insulin secretion by the pancreas.
Chronically elevated blood glucose levels and excessive insulin secretion are thought to play important roles in the development of type 2 diabetes. Several large prospective studies have shown the associated of low-glycemic index diets like legumes with reduced risk of developing type 2 diabetes. Obesity is another important risk factor for type 2 diabetes; and it is claimed that low-glycemic diets result in significantly more weight or fat loss than high-glycemic diets. Numerous clinical trials have shown that the consumption of foods with low-glycemic index delays the return of hunger, decreases subsequent food intake, and increases the sensation of fullness compared to high-glycemic index foods.
Thus, diets rich in legumes may decrease the risk of diabetes by improving blood glucose control, decreasing insulin secretion, and delaying the return of hunger after a meal 25. Legumes contain anthocyanins 40 which may lower blood glucose by improving insulin resistance, protecting β cells, increasing secretion of insulin and reducing digestion of sugars in the small intestine 41. It is reported that clinical use of inhibitors of intraluminal α-amylase inhibitors has importance because controlled reduction of starch digestion theoretically could influence carbohydrate uptake in diabetes mellitus and obesity 42.
General claim on biological activity of legume α-amylase inhibitors in weight control, obesity and diabetes is reported 31, 43.
- Cardiovascular Diseases: Currently, great efforts are focused on reducing the risk of coronary heart disease (CHD) and cardiovascular disease (CVD) through dietary interventions 44. Dietary interventions to reduce the risk of CVD include attention to the consumption of types of fatty acids, dietary fibre, isoflavones and antioxidants. Legume foods contribute to all these areas 14; and legumes phytochemicals such as carotenoids and tocopherols may prevent the risk of CVD 16. The promising link between the intake of leguminous foods and reduced risk of CVD and CHD has been reported in several prospective cohort studies.
Presumably, antioxidant properties of natural antioxidants present in legumes may attribute in part to lower incidence of degenerative CVD. The antioxidant effect may counteract oxidative stress-induced endothelial dysfunction and platelet aggregation, which are two key causes of CVD 45. Othermajor risk factor of CVD that can be modulated by dietary intervention is blood cholesterol 46. A number of dietary agents, including soluble fibres and plant sterols lower cholesterol levels in serum. Plant sterols inhibit cholesterol absorption and viscous fibers increase bile acid excretion 44. Legumes are loaded with fiber and provide a good mix of water soluble and insoluble fibers. The soluble-fiber is known to have a cholesterol-lowering effect and thereby can decrease risk of cardiovascular diseases 4, 19, 25, 46.
Generally, among the mechanisms that have been proposed to explain the cholesterol-lowering effect of legume seeds, the most commons are the physiological action of legume components such as phytic acid, dietary fiber, saponins, phytosterols, proteins, peptides, and their amino acid profiles 47. Legumes contain high levels of antioxidants, vitamin B6, folic acid 19 and they are fairly good sources of thiamin and niacin 48. High levels of homo-cystine damage the walls of the arteries; and vitamin B6 and folic acid aid in lowering the levels of homocystine, which in turn can reduce the risk of stroke, heart attack or vascular disease. Folic acid is also important in preventing birth defects 19, 25 and in reducing the risk of neural tube defects 4. Moreover, legumes are generally, low in sodium and rich in minerals such as potassium, calcium, copper, and magnesium.
Low dietary intake of sodium and high dietary intake of potassium, calcium, and magnesium have been associated with a reduced risk of cardiovascular disease, by helping to lower blood pressure, in epidemiologic studies 19, 25, 49.The low glycemic index values of legumes means that they are less likely to raise blood glucose and insulin levels, which may also decrease cardiovascular disease risk 25.
- Cancer: Legumes have anti-carcinogenic properties 50 and manystudies have firmly established that polyphenolspresent in legumes and various plant sources exertbeneficial health effects and anticancerproperties. Legumes, beside their high nutritive value, contain significant quantities, hence good source, of polyphenolic compounds such as tannins, flavonoids (e.g., kaempherol, quercetin, anthocyanins), isoflavones (e.g., genistein and daidzein), phenolic acids (e.g., p-hydroxybenzoic acid, vanillic acid, p-coumaric acid, and ferulic acid), and lignans.
Legume polyphenolic compounds act as cancer chemopreventive agents, especially by their antioxidant properties 40 as legumes can serve as an excellent dietary source of natural antioxidants for health promotion and cancer 51.Legume phytochemicals, claimed to demonstrate anticarcinogenic activity, include natural antioxidants, γ-tocopherol, ascorbic acid, soy isoflavones, phytosterols, phytates (inositol hexaphosphate), saponins, fibers, protease inhibitors, lectins, and a variety of polyphenols and phenolic acids. These phytochemicals, if consumed in sufficient quantities, may help to reduce tumour risk and could potentially account for a protective effect. Ascorbic acid, phenolic acids and polyphenols have been associated with reduced cancer risk 14, 16, 21, 43, 50, 52. Phytate has proven anti-cancer action 19; antioxidant effects, and may lower the risk of colon and breast cancer.
Fermentable fibers, in legumes, are precursors of luminal butyrate, with well-known anti-inflammatory and antineoplastic properties 14, 53. Anticancer biological activity of protease inhibitor and lectins is reported 43. Proteases are considered key factors in cancer progression. Therefore, the control of their activity by protease inhibitors appears to be related to the capacity of preventing or blocking tumoral pathologies 31.Evidence exist to suggest that consumption of food containing trypsin inhibitors, as are legumes, may have a role in combating breast cancer in humans; and have anticarcinogenic activity in various tissues in animal models14, 32.
Some legumes may influence estrogen metabolism and thereby decrease the risk of hormone-dependent cancers 36. Although limited, there is some evidence from observational studies that legume intake is inversely related to the risk of prostate cancer 25. Genistein which is one of several known isoflavones that are found in legumes has been shown to inhibit the growth of both estrogen-dependent and estrogen-independent breast cancer cells and prostate cancer cells in vitro 4, 54. A diet with a relatively high glycemic index will increase cancer risk by amplifying cancer promotion via insulin-like growth factor-1 (IGF-I) 55. Thus, low glycemic index of legumes can mean reducing cancer risk.
- Osteoporosis: Osteoporosis is a decline in the mass of bone. Recognizing and managing the factors that contribute to osteoporosis will help to prevent it or modulate its severity. These include the following: adequate exposure to sunlight, consumption of adequate amounts of calcium in the diet and avoiding excessive intake of calcium-excreting products such as phosphates in some sodas56.
The skeletal system serves as one of the main buffering systems in the body; as a result, hydrogen ions produced from the metabolism of sulphur amino acids cause demineralisation of bone and excretion of calcium in the urine. Substituting vegetable and legumes for animal protein may reduce urinary calcium excretion and reduce the risk of osteoporosis14.
Sufficient dietary calcium and protein are necessary for bone health during growth as well as in the elderly 57 and legumes are rich source of these two. Soyfoods and isoflavones have received considerable attention for their potential role in preventing and treating cancer and osteoporosis 4, 58. Lignans from some fruits, vegetables and legumes (Soybean, beans) are reported for their potential health benefits inprevention of cardiovascular disease, cancer, and osteoporosis 59.
- Digestive tract diseases: Dietary fiber is thought to provide important protection against some gastrointestinal diseases and to reduce the risk of other chronic diseases as well 60. Studies about fiber and colon cancer provide modest support for an association between dietary patterns involving higher fiber intake and reduced risk of colon cancer. Dietary fiber may affect risk of large bowel cancers through mechanisms such as altering bile acid metabolism, increasing fecal bulk, or decreasing gut transit time 36.
Legumes soluble fiber and oligosaccharides are recognized as a source of prebiotics, which have been described as ‘colonic foods’ that selectively stimulate the growth of beneficial intestinal microflora 9, 14. Fibers in legumes keep human intestinal system healthy. They keep the bowels healthy and move regularly, improve constipation, and combat against colon cancer and intestinal disorders 19.
SUMMARY: Legumes constitute a part of the diet of nearly all humansand greatly contribute to alleviate malnutrition and sustain good health. The nutrient content (protein, carbohydrate and micronutrients) of legumes contribute to address undernutrition and protein-calorie malnutrition, especially among children and nursing mothers in the developing countries. Legumes are ideally suited to meet two major dietary recommendations for good health- intake of starches and decreased consumption of fat. They are also good sources of quality protein and can be substituted for animal protein sources when complemented with cereals. Thus, supplementing cereal-based diets with legumes is suggested as one of the best solutions to protein calorie malnutrition in the developing countries.
The presence of certain anti-nutritional factors, in legumes, can decrease palatability, diminish protein digestibility and mineral bioavailability; and thereby limit the biological value and acceptance of legumes or pulses as a regular food item. Despite this, recent research has shown potential health benefits of some of these compounds. Therefore, manipulation of processing conditions may be required to remove or reduce only those unwanted components. Fortunately, most of the anti-nutritional factors are reduced or inactivated by traditional cooking and food processing, which not only improves flavor and palatability but also increases the bioavailability of nutrients, by inactivating antinutritional factors.
Owing to their appreciable amount of health-promoting components, legumes play a role in prevention, improvement and/or treatment of disease conditions such as, diabetes mellitus, cardiovascular diseases, cancer diseases (e.g breast and prostate cancers) and lowers blood cholesterol level. Most of these disease conditions are associated with over-nutrition and obesity and are considered as diseases of the rich. Hence, once regarded in Western countries as food for poor people, legumes continue to gain recognition for their importance in health and have now become a ‘health food’ for affluent people.
Legumes have significant role in optimizing the nutritional status of the poor and the health status of the rich, which make them be suitable food items for all types of population in both developed and developing countries. It is, therefore, claimed that including legumes in a health-promoting diet is important in meeting the major dietary recommendations to improve the nutritional status of undernourished as well as over-nourished individuals, and to reduce risk for chronic diseases such as cardiovascular disease, diabetes mellitus and cancer.
- Megat Rusydi MR, Noraliza CW, Azrina A and Zulkhairi A.Nutritional changes in germinated legumes and rice varieties.International Food Research Journal2011; 18: 688-696.
- Mazur WM, Duke JA, Wahala K, Rasku S,and Adlercreutz H. Isoflavonoids and lignans in legumes: Nutritional and health aspects in humans. Nutritional Biochemistry 1998; 9(1): 93-200.
- Tiwari BK, Gowen A, McKenna B. Pulse Foods: Processing, Quality and Nutraceutical Applications. Elsevier Inc, 2011.
- Messina MJ. Legumes and soybeans: overview of their nutritional profiles and health effects. American Journal of Clinical Nutrition 1999; 70: 439S-50S.
- Michaels TE. Pulses, Overview, pp 494-501. Elsevier Ltd,University of Minnesota, St. Paul, MN, USA, 2004.
- Pittaway JK. The effect of chickpea consumption on some physiological and metabolic parameters. University of Tasmania, 2006.
- Rysová J, Ouhrabková J, Gabrovská D, Paulíčková I, Winterová R, Vymyslický T, Prokeš J and HutařM. Food with addition of little-known legumes varieties. Agronomy Research 2010; 8: 339- 344.
- Sandlin C. The model system C. Elegans demonstrates the health benefits of legumes and the potential benefits of legume consumption. Louisiana State University and Agricultural and Mechanical College. In partial fulfillment of the Requirements for the degree of Master of Science in The Department of Food Science, 2010.
- Setchell KDR and Radd S. Soy and other legumes: ‘Bean’ around a long time but are they the ‘super foods’ of the millennium and what the safety issues for their constituent phytoestrogens are? Asia Pacific Journal of Clinical Nutrition 2000; 9: S13-S22.
- Bravo L, Siddhuraju P, Saura-Calixto F. Composition of underexploited Indian pulses. Comparison with common legumes. Food Chemistry 1999; 64: 185-192.
- Machaiah JP, Pednekar MD. Carbohydrate composition of low dose radiation-processed legumes and reduction in flatulence factors. Food Chemistry 2002; 79: 293-30.
- Hoisington D. MP3-Grain Legumes: Enhanced food and feed security, nutritional balance, economic growth and soil health for smallholder farmers; ICRISAT-IN, 2010. URL: https://sites.google.com/a/cgxchange.org/mp3-grain-food-legumes/project-documents
- "Fabales."Encyclopædia Britannica. Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2012.
- Venter CS, Eyssen E. More Legumes for Overall Better Health. Dry bean Producers Organisation, Pretoria. SAJCN (Supplement) 2001; 14(3):S32-S38.
- Chen L, Liu R, Qin C, Meng Y, Zhang J, Wang Y, Xu G. Sources and intake of resistant starch in the Chinese diet. Asia Pacific Journal of Clinical Nutrition 2010; 19 (2):274-282
- Boschin G, Arnoldi A. Legumes are valuable sources of tocopherols. Food Chemistry 2011; 127:1199-1203.
- Carvalho AFU, Farias DF, Rocha-Bezerra LCB, de Sousa NM, Cavalheiro MG, Fernandes GS, Brasil ICF, Maia AAB, de Sousa DOB, Vasconcelos IM, Gouveia ST, Machado OLT. Preliminary assessment of the nutritional composition of underexploited wild legumes from semi-arid Caatinga and moist forest environments of northeastern Brazil. Journal of Food Composition and Analysis 2011; xxx: xxx–xxx.
- Mirabelli M, Shehab R.Nutrition.Clinical Men's Health,2008.
- James. Help stop cancer, diabetes and heart disease. HEALTHPLEGE, 2010.URL: http://healthpledge.com/ health-benefits-legumes
- Sridhar KR, Seena S. Nutritional and antinutritional significance of four unconventional legumes of the genus Canavalia – A comparative study. Food Chemistry 2006; 99: 267-288
- Kalogeropoulos N, Chiou A, Ioannou M, Karathanos VT, Hassapidou M, Andrikopoulos N K Nutritional evaluation and bioactive microconstituents (phytosterols, tocopherols, polyphenols, triterpenic acids) in cooked dry legumes usually consumed in the Mediterranean countries. Food Chemistry 2010; 121: 682-690.
- Iqbal A, Khalil IA, Ateeq N, Khan MS. Nutritional quality of important food legumes. Food Chemistry 2006; 97: 331-335.
- Khattab RY., Arntfield SD, Nyachoti CM. Nutritional quality of legume seeds as affected by some physical treatments, Part 1: Protein quality evaluation. LWT - Food Science and Technology 2009; 42: 1107-111.
- Pedrosa MM, Cuadrado C, Burbano C, Allaf K, Haddad J, Gelencsér E, Takács K, Guillamón E, Muzquiz M. Effect of instant controlled pressure drop on the oligosaccharides, inositol phosphates, trypsin inhibitors and lectins contents of different legume. Food Chemistry 2012; 131: 862–868.
- Anderson JW. Legumes. Linus Pauling Institute's Micronutrient Information Center. Linus Pauling Institute, 2004.
- Newby PK. Plant foods and plant-based diets: protective against childhood obesity. The American Journal Clinical Nutrition 2009; 89:1572S-1587S.
- Abd El-Hady EA, Habiba RA. Effect of soaking and extrusion conditions on antinutrients and protein digestibility of legume seeds. Lebensm.-Wiss. U.-Technol. 2003; 36: 285-293
- Xu B, Chang SKC. Effect of soaking, boiling, and steaming on total phenolic content and antioxidant activities of cool season food legumes. Food Chemistry 2008; 110: 1-13.
- Stoddard F, Lizarazo C, Makela P and Nykanen A. New annual legume crops for Finnish conditions. Department of Applied Biology, University of Helsinki, 2010. URL: Maataloustieteenpäivät 2010. www.smts.fi
- Nagabhushana Rao G and Shrivastava SK.Toxic and Antinutritional Factors of New Varieties of Pea Seeds. Research Journal of Pharmaceutical, Biological and Chemical Sciences 2011; 2(2): 512-523.
- Scarafoni A, Magni C and Duranti M. Molecular nutraceutics as a mean to investigate the positive effects of legume seed proteins on human health. Trends in Food Science & Technology 2007; 18: 454-463
- Hill GD. Plant Antinutritional Factors/Characteristics. 4578-86; Elsevier Science Ltd.; Lincoln University, Canterbury, 2003.
- Liener IE. Plant Antinutritional Factors/ Detoxification. 4587-93; Elsevier Science Ltd.; University of Minnesota, St. Paul, MN, USA, 2003.
- Peterbauer T and Richter A. Biochemistry and physiology of raffinose family oligosaccharides and galactosyl cyclitols in seeds. Seed Science Research 2001; 11(03): 185-197.
- Dixon RA and Sumner LW. Legume Natural Products: Understanding and Manipulating Complex Pathways for Human and Animal Health. Plant Physiology 2003; 131: 878-885
- Kushi LH, Meyer KA, and Jacobs Jr DR. Cereals, legumes, and chronic disease risk reduction: evidence from epidemiologic studies. American Journal of Clinical Nutrition 1999; 70:451S-8S.
- Morris MJ, Velkoska E, Cole TJ. Central and peripheral contributions to obesity-associated hypertension: impact of early overnourishment. Experimental Physiology 2005; 90(5):697-702.
- Chopra M, Galbraith S, & Darnton-Hill I. A global response to a global problem: the epidemic of overnutrition. Bulletin of the World Health Organization 2002; 80 (12): 952-958.
- Boye J, Zare F, Pletch A. Pulse proteins: Processing, characterization, functional properties and applications in food and feed. Food Research International 2010; 43: 414–431.
- Spanou C, Stagos D, Aligiannis N, and Kouretas D Influence of Potent Antioxidant Leguminosae Family Plant Extracts on Growth and Antioxidant Defense System of Hep2 Cancer Cell Line. Journal of Medicinal Food 2010; 13 (1):149-155.
- Sancho RAS, Pastore GM. Evaluation of the effects of anthocyanins in type 2 diabetes. Food Research International 2012; 46: 378-386.
- Kumanan R, Manimaran S, Saleemulla K, Dhanabal SP, Nanjan MJ. Screening of bark of Cinnamomum tamala (Lauraceae) by using α-amylase inhibition assay for anti-diabetic activity.International Journal of Pharmaceutical and Biomedical Research2010; 1(2):69-72.
- Duranti M. Grain legume proteins and nutraceutical properties. Fitoterapia 2006; 77: 67-82.
- Kamal-Eldin A and Moazzami A. Plant Sterols and Stanols as Cholesterol-Lowering Ingredients in Functional Foods. Recent Patents on Food, Nutrition & Agriculture 2009; 1(1): 1-14.
- Wang S, Melnyk JP, Tsao R, Marcone M F. How natural dietary antioxidants in fruits, vegetables and legumes promote vascular health. Food Research International 2011; 44: 14-22.
- Anding J. Legumes-Dry Beans and Peas. Agri LIFE EXTENSION, Texas A&M University System, 1914. URL: http://repository.tamu.edu/bitstream/handle/1969.1/86931/pdf_1254.pdf?sequence=1
- Frota KMG, Mendoca S, Saldiva PHN, Cruz R.J and Areas JAG. Cholesterol-Lowering Properties of Whole Cowpea Seed and Its Protein Isolate in Hamsters. Journal of food science 2008; 73(9): 235-240.
- Graham PH and Vance CP. Legumes: Importance and Constraints to Greater use. American Society of Plant Biologists 2003; 131: 872- 877.
- Bazzano LA, He J, Ogden LG, Loria C, Vupputuri S, Myers L, Whelton PK. Legume Consumption and Risk of Coronary Heart Disease in US Men and Women-NHANES I Epidemiologic Follow-up Study.Arch Intern Med. 2001; 161, 2573-2578.
- Kolonel LN, Hankin JH, Whittemore AS, et al. Vegetables, Fruits, Legumes and Prostate Cancer: A Multiethnic Case-Control Study. Cancer Epidemiology Biomarkers Prevention 2000; 9:795-804.
- Xu, B., Chang, S.K.C., Comparative study on antiproliferation properties and cellular antioxidant activities of commonly consumed food legumes against nine human cancer cells, Food Chemistry (2012), doi: 10.1016/j.foodchem.2012.02.212.
- Mathers JC. Pulses and carcinogenesis: potential for the prevention of colon, breast and other cancers. British Journal of Nutrition 2002; 88 (3): S273-S279.
- Hartman TJ, Albert PS,Zhang Z, Bagshaw D, Kris-Etherton PM, Ulbrecht J, Miller CK, Bobe G, Colburn NH, and Lanza E.Consumption of a Legume-Enriched, Low-Glycemic Index Diet Is Associated with Biomarkers of Insulin Resistance and Inflammation among Men at Risk for Colorectal Cancer. Journal of Nutrition 2010; 140: 60-67.
- Jooyandeh H. Soy Products as Healthy and Functional Foods. Middle-East Journal of Scientific Research 2011; 7 (1): 71-80.
- McCarty MF. Dietary Glycémic Index May Influence Cancer Risk by Modulating IGF-I Activity: A Hypothesis. Journal of Medicinal Food 1998; 1 (2):123–140
- Oyelowo T.Osteoporosis. Mosby's Guide to Women's Health: A Handbook for Health Professionals2007; 161-167.
- Rizzoli R. Nutrition: its role in bone health. Best Practice & Research Clinical Endocrinology & Metabolism 2008; 22 (5): 813-829.
- Yamaguchi M. Regulatory Mechanisms of Food Factors in Bone Metabolism and Prevention of Osteoporosis. The Pharmaceutical society of Japan 2006; 126(11):1117-1137.
- Crujeiras AB, Goyenechea E, Martínez JA. Fruit, Vegetables, and Legumes Consumption: Role in Preventing and Treating Obesity. Bioactive Foods in Promoting Health 2010; 359-380.
- Nutrition, human. Encyclopædia Britannica. Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2012.
How to cite this article:
Gebrelibanos M, Tesfaye D, Raghavendra Y and Sintayeyu B: Nutritional and Health Implications of Legumes. Int J Pharm Sci Res 2013; 4(4); 1269-1279
Mebrahtom Gebrelibanos*, Dinka Tesfaye, Y. Raghavendra and Biruk Sintayeyu
Course and Research Unit of Pharmacognosy, Department of Pharmacy, College of Health Sciences, Mekelle University, Mekelle, Ethiopia
21 December, 2012
23 February, 2013
19 March, 2013
01 April, 2013