A new study suggests that substituting whole grains for refined grains in the diet increases calorie loss by reducing calories retained during digestion and speeding up metabolism and improves healthy gut microbiota and certain immune responses.
The research team analyzed the results from an eight-week randomized, controlled trial with 81 participants to see what effect a diet rich in whole grains, as opposed to a diet rich in refined grains, would have on immune and inflammatory responses, gut microbiota and stool frequency in healthy adults.
“Many previous studies have suggested benefits of whole grains and dietary fiber on chronic disease risk. This study helps to quantify how whole grains and fiber work to benefit weight management and lend credibility to previously reported associations between increased whole grains and fiber consumption, lower body weight and better health,” says Phil J. Karl, PhD, first author of the study, alumnus of the Friedman School of Nutrition Science and Policy at Tufts, former research assistant in the Energy Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at Tufts University in Boston and current nutrition scientist at the U.S. Army Research Institute of Environmental Medicine in Natick, MA.
“The strength of the study is that we found modest effects of whole grain on gut microbiota and measures of immune function in the context of a controlled energy and macronutrient diet where all food was provided to participants, allowing them to maintain their body weight constant, thus eliminating the confounding effect of weight loss associated with increasing fiber consumption on immune and inflammatory markers. Additionally, our study incorporated markers of diet adherence and whole grain consumption, allowing us to more confidently determine the effect whole grains have on the gut microbiota and inflammatory responses,” said corresponding and senior author Simin Nikbin Meydani, D.V.M., Ph.D., director of the nutritional immunology laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston (HNRCA).
The study was published online in the journal American Journal of Clinical Nutrition.