A human nutrition study reaffirmed the health benefits of substituting whole-grain foods like whole-wheat bread, oatmeal, barley, rye, and brown or wild rice for refined-grain products like white bread in the diet.
Scientists with the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA)—jointly run by the Agricultural Research Service (ARS) and Tufts University in Boston, Massachusetts—conducted the study to clarify the role of whole grains in helping regulate weight, blood sugar levels and calorie (energy) use, among other benefits. Unlike refined grains, which undergo extensive milling or other processing, whole grains are sold for eating with their bran and other constituents intact—all rich in vitamins, minerals, fiber and other nutrients.
According to Susan Roberts, director of the Center’s Energy Metabolism Laboratory, the study was the first to strictly control participants’ diet, weight and type of whole-grain products they consumed. Previous clinical trials didn’t incorporate these important study design criteria, leaving the benefits of whole-grain diets—especially on weight management—open to being questioned.
In the eight-week study, published last year in the American Journal of Clinical Nutrition, the researchers determined the weights and energy intake needs of 81 participants (healthy, nonsmoking men and women ages 40 to 65) and started them on a diet free of whole grains. At week two, the researchers randomly switched some participants to diets containing the daily recommended allowance of whole grains (a minimum of three ounces for women and four ounces for men every day).
Among the results, participants in the whole-grain group lost approximately 100 more calories per day than refined-grain eaters-the equivalent of walking briskly for 30 minutes. The researchers attributed the lost calories in the whole-grain group primarily to increased metabolic rate and increased fecal energy losses (calories excreted rather than burned or stored). The whole-grain diet also gave a moderate boost to beneficial gut bacteria that help stave off inflammation and pathogens.