Mechanisms of the effects of grains on insulin and glucose responses

Consumption of a number of grains and grain extracts has been reported to c ontrol or improve glucose tolerance and reduce insulin resistance. The inab ility of the body to maintain normal glucose levels or to require excessive levels of insulin to do so has been called glucose intolerance, impaired g lucose tolerance and insulin resistance. These conditions are associated wi th obesity and may be preliminary steps in the progression to type 2 diabet es mellitus. Although dietary goals recommend the consumption of three serv ings of whole grains per day, average consumption in the United States is l ess than one serving per day. There are a number of mechanisms by which gra ins may improve glucose metabolism and delay or prevent the progression of impaired glucose tolerance to insulin resistance and diabetes. These mechan isms are related to the physical properties and structure of grains. The co mposition of the grain, including particle size, amount and type of fiber, viscosity, amylose and amylopectin content all affect the metabolism of car bohydrates from grains. Increasing whole grain intake in the population can result in improved glucose metabolism and delay or reduce the risk of deve loping type 2 diabetes mellitus. Whole grains can provide a substantial con tribution to the improvement of the diets of Americans. A number of whole g rain foods and grain fiber sources are beneficial in reduction of insulin r esistance and improvement in glucose tolerance. Form, amount and method of cooking of these foods as well as the health characteristics, age and gende r of the group of subjects studied are all important factors in the effecti veness of the foods in altering these responses. Dietary recommendations of health organizations suggest consumption of three servings a day of whole grain foods; however, Americans generally fall below this standard. Recent research using various grains and grain products effective in improving ins ulin resistance or lowering glycemic index will be discussed below by possi ble mechanisms of action.