Why Whole Grains Reign


by Karen Baar

Looking for a diet to help beat Type 2 diabetes? Two long-term studies suggest there's more than a grain of truth in the tip to eat more brown rice, barley, buckwheat and oats.

A Harvard Medical School study, published in the American Journal of Public Health in September 2000, tracked the diets of 75,000+ women, ages 38 to 63, for 10 years. When the study began, none had a diagnosis of type-2 diabetes -- the increasingly common form of the disease, which often strikes in middle age.

A decade later, nearly 2,000 of them did.

Whole Grains Reduce Risk

Participants who ate about three servings of whole-grain foods each day were 27% less likely to develop diabetes.

Those who ate the most refined grains -- white rice, pasta, white bread -- had a 57% higher risk of developing the disease.

Similarly, a University of Minnesota School of Public Health study published in the April 2000 American Journal of Clinical Nutrition found that among the 35,000 older women enrolled in the Iowa Women's Health Study -- a long-term study of diet and disease -- those who ate the most whole grains were 21% less likely to develop diabetes over a six-year period.

Although these studies looked only at women, "there's a fair amount of evidence that the same things hold true for men," notes David Jacobs, Ph.D., professor of epidemiology at the University of Minnesota School of Public Health, and an author of the study.

A New Approach to Carbs

The idea that all carbohydrates are not created equal is a new theme in diabetes prevention -- in the past, brown bread and beans were lumped in the same category as crumb cakes and crullers.

"People haven't paid enough attention to the kind of carbohydrate when it comes to type-2 diabetes," says Simin Liu, M.D., Sc.D., principal author of the Harvard Medical School study.

How do whole grains protect? No one knows. But it is clear they offer a package of beneficial nutrients and phytochemicals that could be responsible, either individually or in combination.

"It could be dietary fiber or some of the minerals found in whole grains, such as magnesium, chromium or other minerals not yet studied," suggests Lawrence H. Kushi, Ph.D., an author of the Minnesota study and now Ella McCollum Vahlteich Professor in Nutrition at Teacher's College, Columbia University in New York.

Keeping Blood Sugar in Check

Experts also point to whole grains' positive effects on blood sugar, a key factor in diabetes. A diet that includes beans, vegetables and fiber-rich fruits raises blood sugar levels less dramatically than one heavier in refined grains, flour, sugar, and sugary sodas -- even if the absolute amount of carbohydrates is exactly the same.

Fiber -- especially the kind found in beans, barley and oats -- is one reason certain carbohydrate-rich diets raise blood sugar more slowly than others. Another is "particle size" -- for instance, it takes longer for your body to break down brown rice than brown rice flour.

Since 1981, researchers have been measuring the "glycemic index" -- the tendency of a given amount of food to raise blood sugar levels in the two hours after eating.

Carbohydrates that are slow to break down will release glucose into the bloodstream gradually, and have a lower glycemic index. But foods with a higher glycemic index tend to cause spikes in blood sugar, putting more strain on the pancreas.

"Glycemic load" looks at the total amount of carbohydrates you eat as well as their glycemic index. To reduce your glycemic load, improve the quality of your carbohydrates. In short, eat more whole fruits and vegetables.

Miavita Scientific Advisor Edward Giovannucci, M.D., Sc.D., a co-author of the Harvard study anticipates that "Whole grains and beans will be shown to be more and more important in preventing chronic disease in the coming years. There are a lot of studies in the pipeline."

"We now have solid evidence that diet matters," says Dr. Liu. "Diabetes is a very preventable disease."

Karen Baar writes about food and nutrition in Woodbridge, Conn.