Legumes

Legumes are the collective term used to define all plant products which can be labeled as pod containing seeds. We can enrich legume-diet by adding beans and soybeans in our diet. There are a variety of legumes that are obtained from different plant sources such as dry beans, broad beans, dry peas, chickpeas, lentils, soybeans, lupins, mung beans, lotus, sprouts, alfalfa, green beans and peas and peanuts. However, the legumes and pulses are interchangeable words, however, there is a minor difference between these two dietary items. Pulses are dry seeds of leguminous plants and exclude green harvested legumes (e.g. peas, sprouts) and oil extracting legumes (e.g. peanut, soybean). Legumes have the potentiality to treat and prevent different chronic diseases, including Cardio Vascular Diseases (CVD), diabetes and cancer. Since 5500BC, legumes are enlisted in our dietary chart and considered to be one of the initial crops that is cultivated by our ancestors. [1]

 

Nutritional & Phytochemical background of Legumes, seeds, and sprouts

Legumes are one of the best plant-based dietary protein sources. In addition, low glycaemic index carbohydrates, resistant starch, oligosaccharides are exclusively present in legumes. The resistant starch and oligosaccharides act as a prebiotics and maintain intestinal microbiota1. The other micronutrients like vitamins B including thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, folate, α, β and γ tocopherols and phylloquinone are also present in legumes along with several trace minerals like iron, zinc, calcium, magnesium, selenium, phosphorus, copper and potassium. There is study evidence which supports that sufficient consumption of legumes provide adequate iron and prevents anemia, especially in adolescents and pregnant women.[2]

  • The phytochemicals like lectins, phytoestrogens, phytosterols, saponins, phytates, phenolic acids, and flavonoids are present in legumes and play different health benefits roles such as:
  • Phytosterols, isoflavones, lignans, saponins and alkaloids, oligosaccharides and phytates provides protection from cardiovascular disease, diabetes and cancer1.
  • Polyphenolics have antioxidant and anti-carcinogenic activity1.  
  • Isoflavones such as genistein, daidzein, coumestrol, formononetin and biochanin-A act as act as phytoestrogens.[1]
  • Saponins and Phytosterols lowers cholesterol level [1]
  • Phytic acid like inositol possess bowel cancer preventive action and reduce the diabetes-related complications. [1]

Sprouts and seeds are good sources of phenolic and flavonoids compounds, which act as potent antioxidant. [3]

In this article, we will discuss a variety of legumes and their health benefits due to the presence of several bioactive phytochemicals, macro, and micronutrients.

 

Lupin legume

This legume is collected from Lupinus plant species which belongs to the Fabaceae family. This has two varieties - bitter and sweet lupins. The difference between these two lies in the alkaloid contents.  Bitter lupin has some toxic alkaloids and presently not used for human consumption. The alkaloid contents of bitter lupin are modified by the breeding process. Sweet lupins are free of alkaloids. [1]

Sweet lupins are the highest source of protein (38%) and fibers (30%). They contain a very little amount of carbohydrate (6 to 10%) and has a low glycemic index. The low phytates and saponins content of Sweet lupins is advantageous, as this legume does not require any heat or chemical process and even it can be eaten as uncooked. Therefore, all the bioactive ingredients stay intact in sweet lupins. Following are the benefits of sweet lupins: [1]

Cardio-protective and improve lipid profile

The β-sitosterol is a type of phytosterols present in sweet lupins, is almost 53.6 mg/100 g and play a major role to decrease cholesterol level by blocking its intestinal absorption. Both, animal and human studies provide the evidence that daily consumption of sweet lupin is effective to reduce both LDL and total cholesterol level. Thus, lupins render cardio-protective effect. [1]

Anti-diabetic Effect

The addition of sweet lupin in the diet reduces glycemic index and improve insulin sensitivity due to its high protein and dietary fiber content. Several studies showed that an addition of sweet lupin in the diet of the diabetic patients reduce both fasting and postprandial blood glucose level and normalize insulin level in the blood. Researchers also found that the blood glucose normalizing effect of lupin is due to the presence of conglutin-γ. The conglutin-γ is a glycoprotein and may have insulin-mimetic cellular effect [1].

Wight Management

A high protein and fiber content of lupin provides appetite filling effect and satisfy the hunger. This reduces food craving and assists to reduce the weight. In addition, Lupin has a low glycemic index and the research evidence also showed that lupin markedly decreases the weight of the research participants [1].

Improve bowel condition

The high fiber content of lupin is favorable for bowel health. Lupin fibers maintain the intestinal microbiome by balancing the good and bad bacterial count. Study findings showed that Bifidobacterium spp is increased, whereas C. ramosum and C. spiroforme species is decreased after consumption of lupins for 28 days. Lupins also provide short-chain fatty acids and reduce the fecal pH by inhibiting bile excretion. Thus, it also prevents colorectal cancer [1].   

Breast cancer preventive action

Lupin is a good option for the women having a high risk for estrogen-induced breast cancer, as it has phytoestrogens [1].   

Caution: Individuals having a history of food allergy with other legumes and nuts should take the precautionary measure of Lupinus or avoid to take it.  

 

Soya beans

Since ages soya beans are a part of the human dietary list. Soya beans are widely cultivated not only for its oil production but also for its rich lipid profile which makes it a healthy legume. The nutrient profile of soya beans includes several important nutrients like high-quality protein, polyunsaturated fatty acids, carbohydrates and dietary fibers.  The bioactive phytochemicals present in soya beans are isoflavones, phytosterols, lecithins, soluble fibers, saponins, and polysaccharides. These phytonutrients solely or collectively follow different mechanism of action to provide exclusive health benefits [4].

Improves lipid profile

The lecithins and saponins contents of soya beans actively participate in lipid metabolism.  Phytosterols and linoleic acid reduce total cholesterol level and control hypercholesterolemia. Soya protein can reduce LDL (bad) cholesterol level which provides multiple health benefits including cardioprotective, antioxidant and renal functioning improvement. The LDL- lowering effect of Soya protein assist to improve endothelial functioning and thus reduce the cardiac and renal load. Research studies showed that combination of soy fibers and soy proteins provide an additive effect to produce hypocholesterolemic effect [4].    

Estrogen-mimetic effect

Isoflavones content in Soya beans is unique flavonoids, which are mainly classified under phytoestrogens. Daidzein, genistein, and glycitein are the three isoflavones that elicit estrogenic effects by increasing estrogen concentration in the blood and provide several significant physiological effects in mammalians4.  

Cardio-protective effect

Phytoestrogens of Soybeans reduce the risk of CVD after menopause by increasing the estrogen level. A study performed in Chinese women revealed a significant reduction of blood pressure, plasma triglycerides, and C - reactive protein concentrations after incorporating soy in diet [4].  

Anti-hypertensive

Isoflavones act as an antihypertensive. Estrogen-mimetic effect of Isoflavones improve endothelial nitric oxide production and provides vasodilation. They also increase renal blood flow, sodium excretion and inhibit ACE activity. In addition, a higher level of arginine in comparison to lysine also assist to regulate blood pressure [4].  

 Antidiabetic

Isoflavones present in soybeans can reduce the pancreatic β- cell damage. The antioxidant effect of genistein improves insulin secretion by inhibiting tyrosine kinase. In addition, genistein also positively alter β cell proliferation, insulin secretion and prevents apoptosis by modifying cAMP/PKA signaling and regulating gene expression. Phenolic compounds control postprandial blood glucose level by inhibiting α-amylase and α-glucosidase enzymes. The human trial report provides the evidence that soya beans can reduce blood glucose level [4].

Anti-inflammatory

Genistein isoflavones downregulate pro-inflammatory genes expression and inhibit ROS production. Daidzein activates PPAR-α and γ and inhibits JNK pathway for modulating inflammatory gene expression. Isoflavones have pro-inflammatory cytokines and chemokines lowering effect. However, the combination of these phytochemicals present in soy has a more potent anti-inflammatory effect than individual phytochemicals. The anti-inflammatory and antioxidant effect of soy is effective to control CVD and diabetes [4].

Anti-obesity

Obesity has a link with inflammation. Anti-inflammatory effect of soy isoflavones controls obesity. Isoflavones have anti-adipogenic effects and also up-regulates PPAR-α and γ, which promote the breakdown of fatty acids by stimulating β-oxidation. Black soy isoflavones can reduce liver mass, body mass, control blood glucose level, total cholesterol, and serum leptin concentration level. Few study results also showed that soy diet can give satiety effect and reduce appetite [4].

 

Chickpeas

The scientific name of chickpeas is Cicer arietinum L. Albumins and globulins are the main protein sources present in Chickpeas. A smaller amount of glutelins and prolamines are also present in it.

Nutritional profile

Chickpeas spread provides 50 kcal energy, 4.29 carbohydrates, 2.37 protein, 2.88 total fat (with minimal saturated fat), 1.8g fibers and 114 sodium per 2 tablespoonful servings. The natural nutrient-rich score of chickpeas is 98.42, which is much more than other dietary ingredients including cheese, peanut butter or cream.[5] Following are health benefits obtained from Chickpeas:

Weight management   

Low energy density, high fiber, and moderate protein content make an anti-obesity property of Chickpeas. It also provides a low glycemic index. [5]

Anti-diabetic

The dietary fat content delays the carbohydrate absorption, slow down the gastric emptying. Thus, it maintains the low glycemic index and lowers the blood glucose level. It also improves insulin response.  [5]

Cardiovascular disease protection

Chickpeas reduce adiposity and inhibit hepatic enzyme activities to reduce the cholesterol synthesis in the liver. Thus, it lowers down total cholesterol and LDL level. [5]

Anticancer

Chickpeas consumption increases Butyrate level, which is a short chain fatty acid and can suppress cell proliferation and initiate apoptosis. Thus, Chickpeas may decrease colorectal cancers risk. Lycopene, Biochanin A, and saponins are bioactive phytochemicals present in chickpeas which render anticancer effect. Chickpea seed coat fiber has an antioxidant effect and reduces lipid peroxidation and toxic effect. [5]

Improve Gastro-intestinal functioning

Chickpeas is an adequate source of insoluble dietary fibers and prevent constipation by improving bowel movement without producing any habitual effect.[5]

 

References

  • Antigone Kouris-Blazos, Regina Belski, Health benefits of legumes and pulses with a focus on Australian sweet lupins. Asia Pac J Clin Nutr 2016;25(1):1-17
  • Kumar Ganesan, Baojun Xu, Polyphenol-Rich Lentils and Their Health Promoting Effects. Int. J. Mol. Sci. 2017, 18, 2390; doi:10.3390/ijms18112390
  • Chon SU. Total polyphenols and bioactivity of seeds and sprouts in several legumes. Curr Pharm Des. 2013;19(34):611224.
  • D. Dan Ramdath, Emily M. T. Padhi, Sidra Sarfaraz, Simone Renwick, Alison M. Duncan. Beyond the Cholesterol-Lowering Effect of Soy Protein: A Review of the Effects of Dietary Soy and Its Constituents on Risk Factors for Cardiovascular Disease. Nutrients 2017, 9, 324; doi:10.3390/nu9040324
  • Taylor C. Wallace, Robert Murray, Kathleen M. Zelman. The Nutritional Value and Health Benefits of Chickpeas and Hummus. Nutrients 2016, 8, 766; doi:10.3390/nu8120766.