Background: Even though dietary fiber has been hypothesized to reduce the risk of coronary heart disease, few large epidemiological studies have examined this relation with good methodology.
Methods and results: The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study was a randomized, double-blind, placebo-controlled trial with daily supplementation of alpha-tocopherol and/or beta-carotene. Of the participants, 21930 smoking men aged 50 to 69 years who were free of diagnosed cardiovascular disease and had completed a validated dietary questionnaire at baseline were followed for 6.1 years. We monitored the incidence of major coronary events (a combination of first nonfatal myocardial infarction and coronary heart disease death; n = 1399) and mortality from coronary heart disease (n = 635). Both entities had a significant inverse association with dietary fiber, but the association was stronger for coronary death. For men in the highest quintile of total dietary fiber intake (median, 34.8 g/d), the relative risk for coronary death was 0.69 (95% confidence interval, 0.54 to 0.88; P < .001 for trend) compared with men in the lowest quintile of intake (median, 16.1 g/d). With an adjustment for known cardiovascular risk factors, intake of saturated fatty acids, beta-carotene, vitamin C, and vitamin E did not materially change the result. Water-soluble fiber was slightly more strongly associated with reduced coronary death than water-insoluble fiber, and cereal fiber also had a stronger association than vegetable or fruit fiber.
Conclusions: These findings suggest that independent of other risk factors, greater intake of foods rich in fiber can substantially reduce the risk of coronary heart disease, and particularly coronary death, in middle-aged, smoking men.