Molecular Diversity in Pulse Seed Starch and Complex Carbohydrates and Its Role in Human Nutrition and Health

Seven major pulse crops account for approximate to 90% of global pulse production. Pulses are an important component of human nutrition as sources of proteins, carbohydrates, and minor nutrients such as vitamins and minerals. The major pulse seed storage polysaccharide is starch, which is made up of highly branched amylopectin and sparsely branched amylose. Pulse starches generally contain a higher concentration of amylose as compared to cereal and tuber starches. The nonstarch complex carbohydrates are major components of dietary fiber including cellulose, hemicellulose, and pectic polysaccharides with considerable structural diversity. Diets rich in pulses are associated with health benefits such as reduced calorific content, reduced or no effect on blood glucose levels (low glycemic index), and improved heart health. These health benefits have been attributed to the high amylose concentration (>30%) that gives rise to resistant starch that, along with dietary fiber, remains undigested in the small intestine but is fermented by the microbiota in the colon. Colonic fermentation increases the growth of beneficial bacteria and production of short chain fatty acids which have been associated with reduced risk of colon cancer. Clinical trials with human subjects to confirm the beneficial effects of diets rich in pulses are inconclusive. Advances in genetic strategies to develop pulse seeds with desired carbohydrate concentration and composition, carbohydrate structure characterization, combined with utilization of in vitro and in animal models may be helpful to identify carbohydrate structure function relationship responsible for beneficial effects on human health associated with pulse consumption.