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High-Fiber Diet Lowers Insulin

People who eat more unrefined carbohydrates have lower insulin levels and, therefore, a lower risk of heart disease, according to the 10-year Coronary Artery Risk Development in Young Adults study that tracked the evolution of risk factors among young adults in four parts of the country.

David Ludwig, M.D., Ph.D., of Children's Hospital in Boston studied 2,909 healthy adults, both black and white, ages 18 to 30. The study population was divided into five smaller groups according to a ratio of dietary fiber to caloric intake. Among both blacks and whites, the higher the ratio, the lower the insulin levels.

Elevated circulating insulin levels are thought to contribute to several heart disease risk factors including high blood pressure, obesity and high LDL cholesterol levels. A meal high in refined carbohydrates is quickly absorbed, and sends insulin levels soaring. Unrefined carbohydrates such as whole grains, starchy vegetables or fruit remain in the stomach longer, which delays insulin increases.

These results raise the interesting possibility that fiber may play a greater role in determining cardiovascular disease risk than total or saturated fat, says the author.

This study did not determine the dietary source of fiber or whether it was soluble or insoluble. Nor did researchers assess the nutrients found in fiber, such as phytochemicals, magnesium or vitamin E.

—Journal of the American Medical Association 1999 Oct 27; 282:1539-46.