Bean Institute

By Sruti Chandrasekaran and Nanette Steinle, MD

Excess energy intake, high intakes of saturated and transfatty acids and high intakes of fiber-depleted refined grain foods have been proposed as factors contributing to the development of type 2 diabetes mellitus. Diets high in fiber, especially soluble fiber, are associated with an improvement in serum lipid, glucose, and insulin concentrations among obese individuals and those with type 2 diabetes (1). Diets that include fruits, vegetables, whole grain cereals, dietary fiber, fish and polyunsaturated/ monounsaturated fatty acids may protect against the development of type 2 diabetes and improve measures of glucose homeostasis in both healthy subjects and those with the disease (1-3).

Type 2 diabetes is characterized by insulin resistance and hyperglycemia.  Obesity is present in up to 70% of individuals with type 2 diabetes.  Dietary factors that reduce obesity and improve insulin sensitivity are beneficial for individuals with diabetes.  High fiber and protein rich foods, including dry beans, promote satiety by stimulating hormones such as cholecystokinin, a gut derived hormone involved in the regulation of gastric emptying and mediating satiety signals in the central nervous system. Test meals including dry beans increase post prandial cholecystokinin (4). Postprandial rise in cholecystokinin has been associated with reduction of plasma glucose and insulin concentrations among individuals with diabetes (5).  Including dry beans in the diet may benefit individuals with diabetes by promoting satiety, energy balance, and by moderating postprandial glucose and insulin levels.
High fiber diets reduce post prandial glucose levels, may improve insulin sensitivity, and reduce inflammation (4).  One mechanism whereby postprandial glucose is improved by complex carbohydrate is thought to involve reduced carbohydrate absorption.  Most legumes contain amylase inhibitors, thus reducing hydrolysis of carbohydrate (6).  Amylase inhibition leads to reduced postprandial glucose and insulin levels, increased resistance of starch to digestion, and increased activity of colorectal bacteria. Dry beans are also rich in phytates, soluble fiber and tannins, all of which correlate inversely with carbohydrate digestion and glycemic response (7).
The study of the relationship between human health and microorganisms colonizing the human body is an emerging science.  Microorganisms living on and in the human body encode metabolic pathways that we as humans have not evolved on our own, suggesting that our microbial partners play key roles in maintaining human health. Compositional changes in animal and human gut microbiota have been linked to obesity and diabetes (8).  Host diet is one of the major determinants for the persistence of a given colonizing gastrointestinal bacterium (9,10), and alterations in dietary constituents influence the composition of the gut micro biome, as well as the genes those microbes express (11, 12). The unabsorbed starch from dry beans consists mainly of alpha-glucan molecules and oligosaccharides, key fuels of health promoting bacteria in the gastrointestinal tract (13).  One potential mechanism whereby dry beans benefit obesity and diabetes may be through altering the gut microbiome composition and their gene expression.  Human studies addressing this question will provide important insights into the mechanisms whereby dry beans improve metabolic parameters in obesity and diabetes via altering gut microbial content and activity.

Long standing diabetes can lead to chronic kidney problems and diabetic nephropathy. The pathogenesis of diabetic nephropathy is complex and dietary protein restriction appears to slow the progression of diabetic nephropathy (14). The acute effects of animal- compared with vegetable-protein meals in diabetic and control subjects are not very clear.  Clinical observations led to the soy-protein hypothesis that substitution of soy protein for animal protein may result in reduced hyperfiltration, reduced urinary albumin excretion, and protection from diabetic nephropathy (15, 16).  Additionally, an increase in HDL cholesterol and reducted total-to-HDL cholesterol ratio and improved LDL-to-HDL cholesterol ratio results from dry bean consumption, factors that should be beneficial for type 2 diabetic patients at increased risk of developing cardiovascular disease(16). It is advisable therefore, that persons with diabetes moderate their animal protein intake and substitute vegetable protein for animal protein. A diet including soybeans, lentils, and legumes is a good alternative to animal protein.

Dry beans and legumes are ideally suited to meet major dietary recommendations for individuals with diabetes, including increased consumption of complex carbohydrates and decreased fat.  Legumes supply vital nutrients to the diet, yet are low in fat and sodium and contain no cholesterol.  Legumes are also a cost effective ingredient in sustaining human nutrition.

Source: http://www.dietbites.com/Diet-2/beans-calories-nutrition-info.html

About the Authors

Dr. Nanette I. Steinle, MD, is an assistant professor of medicine at the University of Maryland, Baltimore, where she teaches in the medical school.  She is co-course director of cell and molecular biology, she teaches nutrition in the physiology and therapeutics course, and she also works in the clinical components of the medical curriculum.

Dr. Steinle’s major research interests are the molecular and genetic aspects of blood pressure regulation, obesity, metabolic syndrome, and eating behavior.  She published the first genome-wide scan of eating behavior traits.  Currently, she is studying candidate genes which may regulate eating behavior.

Sruti Chandrasekran completed an internal medicine residency at the University of Buffalo, New York, and is board certified in internal medicine. She is currently an endocrinology fellow at the University of Maryland, Baltimore.

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