“A pulse a day keeps the doctor away”

recent studies show the nutritional interest of pulses if new fiber and bioactive peptide properties have been found. These results encourage researchers to proceed in a fractionation process with a view to developing enriched healthy foods for different groups of people.

Author: Paascale Mollier

INRA – L’Institut National de la Recherche Agronomique

Starch and Fiber

Legumes are high in starch and fiber. This means that they have a low glycemic index (1), around 40, while the glycemic index of white bread is 100, that of rice 90 and that of potatoes 110. Fiber has other benefits as well. Soluble fiber lowers cholesterol. This effect has been clearly demonstrated by a meta-analysis of the findings in various publications (Bazzano et al., 2011). This fact was recently proven in a study in which two servings a day of legumes were given to elderly patients (150g / day) for two months. (Abeysekara et al., 2012). Insoluble fiber produces buitrate when fermenting, this can reduce the incidence of colorectal cancer. Another recent study emphasized the positive effects of insoluble fiber in lupins on gut function (Fechner et al., 2013).

Micronutrients

Legumes contain iron, potassium, calcium, selenium, magnesium, polyphenols, and vitamins B1, B3, and B6.

Proteins for the future

The growing world population, together with a higher standard of living in developing countries, will lead to a global increase in the demand for protein, mainly of animal origin. Prospective studies have shown that demand cannot be met. Among other possible sources of protein, including insects and algae, legumes are the most realistic alternative for now, as they are already available.

Quick and easy digestion of legume proteins

Legume flours and isolates have high digestibility (2). Anti-nutrients such as protease inhibitors, tannins and lecithins, which could negatively affect digestibility, are destroyed by cooking.

The digestion rate is a new criterion to consider when determining the nutritional quality of proteins. Those that are digested quickly are beneficial for the growing population of older people who need a higher intake of amino acids to activate protein synthesis and fight against muscle loss and sarcophénia (Dardevet et al., 2013). However, differences in the digestion rate of legume proteins have yet to be measured, especially compared to the digestion rate of animal proteins.

Complementary relationships between the different types of plant proteins

Legumes are high in arginine and lysine, but low in methionine and cysteine. Therefore legumes can be associated with other sources of prorteins – cereals in particular, which are low in lysine but are well balanced in other amino acids – in combinations such as: chickpea / durum wheat or kidney beans / corn. With this objective, INRA studies are being carried out to develop formulas to make pasta that combine durum wheat and legumes (3), for example a pasta made with beans. This research has demonstrated the technological possibility of producing pasta with a certain content of legumes (35%), while maintaining the standard production methods.

Bio-active amino acids and peptides

New research has shown that certain amino acids and peptides derived from protein digestion have various properties that influence the central nervous and vascular systems. It is currently well known that some amino acids act as signals, stimulating protein synthesis in the case of leucine or synthesizing nitrogen oxide (NO) in the case of arginine, which produces beneficial peripheral vasodilation in cases of hypertension. Legume proteins are rich in this amino acid. Currently there are many projects underway to study the anti-hypertensive effect of legume protein hydrolysates (lentils, soybeans, peas, lupins) by inhibiting angiotensin-transforming enzymes (Boscin et al., 2014)

The nutritional benefits of legume proteins are an incentive to carry out complementary studies, and to investigate the extraction and fractionation processes to develop specially enriched foods for various population groups, such as the elderly or people with great physical activity.

(1) Glycemic index: ability of a food to release glucose into the blood more or less quickly after ingestion. It allows diabetics to monitor their diet by choosing foods with a low glycemic index (International Table Foster-Powell et al., Am J Clinic Nutr 2002, 76 5-56).

(2) UMR Physiology of Nutrition and Food Behavior AgroParis Tech (Daniel Tomé’s Team).

(3) Pastaleg program.