The Last Word on Fiber and Heart Attack?

Summarized by Robert W. Griffith, MD
June 18, 2004

Introduction

By now everyone knows that eating plenty of fiber is good for you, but it doesn't hurt to review the benefits on heart health. Fiber can reduce the risk of coronary artery disease by several possible mechanisms - improving blood lipid profiles, lowering blood pressure, improving insulin sensitivity, and by a fibrinolytic (anti-clotting) activity. A group of eminent researchers have analyzed the results of 10 controlled studies on the role of dietary fiber in the risk of developing coronary heart disease. Their findings are published in the Archives of Internal Medicine, and are summarized here.

What was done

Ten major studies have been published that examine the association between dietary fiber intake and the risk of coronary heart disease. The researchers retrieved the raw data from each study so that they could be pooled for the analysis.

Diets were measured in each study at baseline using food frequency questionnaires. Total fiber intake was calculated, as well as fiber intake from three different food groups (cereals, fruits, and vegetables) and from insoluble (e.g. cellulose) and soluble sources (pectins, gums, etc).

All reported cases of fatal and non-fatal heart attack in study subjects were established using standard criteria. The relative risk (RR) of having a heart attack (myocardial infarction, or MI) was calculated for each 10-gram per day increase in the different types of fiber eaten.

What was found

There were over 91,000 men and 251,000 women in the pooled analysis. Their ages at baseline ranged from 35 to 98, with an average age of 52 years. The duration of follow-up varied from study to study, between 6 and 10 years; there were over 2.5 million person-years of follow-up all together.

Statistical analyses were used to make adjustments for age, energy intake, smoking, body mass index, physical activity, education level, alcohol use, vitamin use, high cholesterol, and high blood pressure.

After these adjustments, it was seen that each 10-gram daily increase in total fiber was linked to a 14% reduction in the risk of having a fatal or non-fatal heart attack. That is to say, a person eating 10 grams more of fiber daily was 0.86 times as likely to have a heart attack as someone eating an average amount of fiber.

For the same increase in total fiber consumption, there was a 27% reduction in the risk of having a fatal heart attack, i.e. the RR here was 0.73.

For cereal, fruit, and vegetable fiber intake, the RRs were 0.90, 0.84 and 1.00, respectively, for all heart attacks, and 0.75, 0.70 and 1.00, respectively, for fatal heart attacks. This shows that fiber from cereal and fruit had a protective effect, while vegetable fiber didn't.

What the numbers mean

Pooling these ten studies provided a very large data base, so that considerable confidence can be placed in the results of analysis. Quite clearly, eating more dietary fiber obtained from cereals and fruits will provide a measure of protection form heart attacks - both non-fatal and fatal. While the fiber obtained from vegetables isn't protective in this way, vegetables contain so many vitamins and minerals that they clearly belong in everyone's diet.

This analysis provides good reason to eat plenty of fiber, every day; if in doubt about the fiber content of your cereal, read the label!

Source

• Dietary fiber and risk of coronary heart disease. MA. Pereira, E. O'Reilly, K. Augustsson,  et al., Arch Intern Med, 2004, vol. 164, pp. 370--376

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