US: New US research adds to the growing body of evidence that a diet rich in whole grains can have a beneficial effect on health, finding that the grains can help maintain a healthy weight, reduce blood sugar levels, and increase calorie (energy) use.
Carried out by scientists from 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, the study looked at 81 participants over an eight-week period to compare the effect of a diet free from whole grains to one rich in whole grains.
The researchers measured the weights and calorie (energy) intake needs of the participants, who were all healthy, non-smoking men and women ages 40 to 65, and put everyone on a whole grain-free diet.
In week two of the study some participants were switched onto a diet that included the daily recommended allowance of whole grains — a minimum of three ounces for women and four ounces for men.
During the eight weeks the researchers recorded the participants’ insulin and blood sugar levels, resting metabolic rates (energy expenditures while sedentary), and how well they stuck to either diet.
The results showed that participants in the whole-grain group lost around 100 more calories per day than those in the group eating refined grains — the equivalent of walking briskly for 30-minutes — possibly due to whole grains increasing metabolic rate and increasing energy loss through feces.
In a tandem study carried out by HNRCA’s Nutritional Immunology Lab, researchers also found that a whole grain rich diet had a beneficial effect on gut microbiota, inflammation, and immune defense.
The team pointed out that the whole grain diet followed in the study included products made from whole grain flour and only one type of grain and that consuming intact whole grain kernels rather than flour, or a mixture of grains, may bring even greater benefits.
Whole-grain foods include whole-wheat bread, oatmeal, barley, rye, and brown or wild rice. Unlike refined grains such as white rice and white flour, whole grains do not have their nutrients stripped away through processing and are rich in vitamins, minerals, fiber, carbohydrates, and phytonutrients.
The findings can be found published online in the American Journal of Clinical Nutrition.