You may have heard it before, but it bears repeating: eating high-fiber, whole-grain foods, such as whole-wheat bread and whole-grain breakfast cereal, may be protective against type 2 diabetes. Among the latest evidence is a study that finds a lower risk of type 2 diabetes in men who had a high intake of whole grains. The results are published in the American Journal of Clinical Nutrition.

Studying male health professionals

Boston-area researchers used data from the Health Professionals Follow-up Study, which began in 1986 with more than 50,000 male health professionals aged 40-75. Of those initially recruited, 42,898 qualified for this study; at the study's start, none had a history of diabetes, cancer, or heart disease.

The subjects completed detailed dietary questionnaires three times (every 4 years) over a period of 12 years. At the 12-year point, 1,197 men had developed type 2 diabetes.

Whole grains associated with lower risk for type 2 diabetes

To find an association between whole-grain intake and risk for diabetes, the researchers grouped the men according to their intake of whole-grains. In looking at the data, they accounted for other factors that could affect the risk of diabetes, such as age, physical activity, cigarette smoking, alcohol intake, and a family history of diabetes.

The men with the highest intake of whole grains - an average 3.2 servings per day - had a 42% lower risk for type 2 diabetes, compared with men who ate only about ½ serving per day. In the group with the highest intake of whole grains, cereal was the most common source of whole grains.

More evidence that we should be eating whole grains

It's not possible from this type of study to say for sure what led to the reduced rate of diabetes among men who ate a whole grain-rich diet. These men also tended to eat more produce and less fat and were less likely to smoke - all good habits that would help them stay healthy.

Nevertheless, the authors offer several possible explanations for their findings. Whole grain foods substantially boost fiber intake, and a high-fiber diet may help control high blood insulin levels. Whole grains are also a good source of magnesium, a mineral linked in previous studies to better insulin and blood sugar control.

How to get your whole grains

To increase your intake of whole grains, try replacing refined grains, such as white rice and white bread, with whole-grain versions, such as brown rice and whole-wheat bread. (Make sure the first ingredient in the bread is whole grain, since some products are made with refined flour and then darkened with molasses for color.)

When making muffins, breads, or pancakes from scratch, substitute whole-wheat flour for some or all of the white flour. And for breakfast, opt for whole-grain hot and cold cereals, instead of English muffins, waffles, and pastries.

As you increase your intake of whole-grains, you may need to increase your fluid intake as well, to help your digestive system process the extra fiber you'll be eating.