June 03, 1999
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JoAnn Manson, associate professor of medicine and of epidemiology, studies how a high-fiber diet can lower the risk of heart disease. Photo by Kris Snibbe.

HARVARD GAZETTE ARCHIVES

Breakfast of Champions

Cereal Reduces Heart Attack Risk For Women

By William J. Cromie

Gazette Staff

Whole-grain cereals beat bagels and muffins as the best breakfast for women trying to protect themselves against heart disease, according to a Harvard study.

Any diet high in fiber reduces the risk of heart attacks and death from heart disease, the researchers found, but cereal fiber is particularly effective. This conclusion comes from a 10-year study of 68,782 women between the ages of 37 and 64 years.

"Our results provide evidence that an increase in food high in dietary fiber, especially cereal products, may be protective against coronary heart disease in women," the researchers reported in the June 2 issue of the Journal of the American Medical Association. "This provides further reason to replace refined forms of starch with whole-grain foods."

Previous studies of men concluded that food rich in fiber, particularly cereals, also protect them against heart disease. However, "we found a stronger apparent effect of cereal fiber among women in our study than previously reported for men," said JoAnn Manson, co-director of women's health at Brigham and Women's Hospital in Boston and Harvard Medical School.

Heart disease is the biggest killer of both males and females in the United States. Worldwide it killed more than 7 million people last year.

Fiber and Cancer

Earlier this year, another Harvard study concluded that high- fiber diets do not reduce the likelihood of colon and rectal cancer. But researchers urged people not to stop eating the recommended 25 to 35 grams of fiber a day because of evidence that it protects against heart disease, diabetes, and digestive disorders.

This latest study increases the weight of that evidence. Alicja Wolk of the Karolinska Institute in Sweden worked at Harvard with Manson and other colleagues at the Harvard School of Public Health, Harvard Medical School, and Brigham and Women's Hospital to analyze questionnaires completed by 68,782 nurses from 1984 to 1994. The questionnaires covered diet, fiber intake, and heart disease. More than 400 of the women suffered heart attacks and 162 died from heart disease during the study.

Answers given by the women showed that those who consumed a median of 23 grams a day of fiber had a 47 percent lower risk of major heart disease compared with those who ate half that amount, or a median of 11.5 grams a day. Even after accounting for differences in age, smoking, exercise high blood pressure, use of multivitamins and other factors, those who ate the most dietary fiber enjoyed a 23 percent lower risk than those who ate the least amount.

The researchers then separated different sources of fiber -- cereals, vegetables and fruit -- to determine if one was more effective than the others. Breakfast cereals took the prize.

One cup, or serving, of a wheat, oat, or rice bran cereal has about 5 grams of fiber. Other foods high in cereal fiber include oatmeal, whole-wheat breads, whole-grain rice, and barley.

Fiber reduces levels of total cholesterol and of its most harmful component (low density lipoprotein). But, the researchers noted, that benefit does not fully account for the large reduction in heart-disease risk found in their study.

Other plausible mechanisms, they say, could include increased sensitivity to insulin and lower levels of blood fats known as triglycerides. "These factors may be especially important in women," Manson points out, "because diabetes and high levels of triglycerides appear to be stronger risk factors for coronary heart disease in women than in men. There may be other biological mechanisms involved as well, including a reduction in the risk of blood clotting."

 


Copyright 1999 President and Fellows of Harvard College