Harvard Health Letter

Fiber on a winning streak

Results from the NIH-AARP Diet and Health Study reported in 2011 show that high intake of fiber is associated with a lower risk of dying from a heart attack or stroke. That's a little ho-hum: other studies have come to the same conclusion. More novel was the finding that linked a high-fiber diet to a lower risk of dying from infectious and respiratory diseases. And fiber from grain sources was associated with a lower risk of dying from any cause during the study's nine years of follow-up.

A few years ago, fiber seemed like another false hope after it fizzled in some important clinical trials as a colon cancer preventive. The NIH-AARP study also came to an ambiguous conclusion about fiber and cancer: high intake was protective in men but not in women. But aside from the cancer findings, fiber has been on a bit of a roll lately.

Explanations for protection against infectious and respiratory disease rely on educated guesses that fiber has anti-inflammatory effects. Reasons for the heart disease benefits are a little clearer. Fiber interferes with the absorption of cholesterol and blood sugar. Soluble fiber (the kind in beans, peas, oatmeal, and fruit) nudges down cholesterol levels by keeping bile salts from being absorbed. The positive influence on blood pressure may come from fiber's moderating effect on insulin levels.

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