July 25, 2002

(American Journal of Clinical Nutrition) -- Diets rich in whole grains protect against cardiovascular disease (CVD), type 2 diabetes, and certain cancers through their favorable effects on risk factors such as high cholesterol and insulin resistance. As part of a long-term community-based study published in the American Journal of Clinical Nutrition, McKeown et al. examined the associations between whole-grain consumption and metabolic indicators of disease risk. The study suggest that high intakes of whole grains may reduce the risk of type 2 diabetes and CVD and may have particular benefits for overweight or obese individuals with diabetes.

Participants in the Framingham Offspring study included 5,135 individuals who were enrolled in 1971 and have been examined every 3 to 4 years since that year. A subset of the original cohort, consisting of 2941 subjects (1338 men and 1603 women) with an average age of 54 years, provided detailed information about their diets and blood samples between 1991 and 1995. All subjects reported a higher average weekly consumption for refined grains (20 servings/week) than of whole grains (8 servings/week). While intake of refined grains had no independent worsening effect on CVD risk, consumption of whole grains was associated with decreased disease risk. Most reported consuming whole grains in the form of cold cereals, dark bread, and popcorn. When the subjects were divided into quintiles according to lower or higher regular servings of whole grains, those in the highest quintile of whole-grain consumption tended to have associated healthy lifestyle habits such as not smoking; taking multivitamin supplements; consuming less meat, alcohol, and saturated fat; and eating more fruits and vegetables. Higher consumption of whole grains was also associated with a lower waist-to-hip ratio, lower total and LDL cholesterol, and lower fasting insulin concentration.

The highest fasting insulin concentrations were found among subjects who were overweight or obese and who were in the lowest quintile of whole-grain consumption. The authors propose that some components of whole grains, such as fiber and magnesium, may play a role in improving insulin sensitivity that could be particularly helpful in preventing and managing type 2 diabetes. In addition, the high fiber content of a diet rich in whole grains may prevent weight gain or promote weight loss by providing a longer feeling of satiety