Higher dietary fiber intake after MI helps reduce mortality risk

Higher dietary fiber intake among myocardial infarction (MI) survivors lowers the risk of subsequent all cause and cardiovascular mortality, according to a prospective study published April 29 in BMJ.

Lead author Shanshan Li, a doctoral candidate at Harvard School of Public Health, Boston, Mass. and colleagues undertook an analysis of two large cohort studies of women and men-the Nurses’ Health Study and the Health Professional Follow-up Study-to evaluate the association of dietary fiber intake before MI, during the period following MI, and any changes that occurred before MI to after MI on survival.

The primary outcomes of study participants (2258 women and 1840 men) were all cause and cardiovascular (CVD) mortality that included death from stroke, MI, and coronary heart disease.  During the 32-year follow-up period in women, 336 of 2258 women died of CVD. In the 22-year follow-up of men, 222 of 1840 men’s deaths were associated with CVD. Total deaths in analysis were 682 women and 451 in men. The median follow-up following MI for women was 8.7 years and for men was 9.0 years, Li and colleagues reported.

“Higher post-MI fiber intake was significantly associated with lower all cause mortality in age-adjusted models for both men and women,” the authors noted.

The researchers evaluated the association of specific fiber intake with all cause and CVD mortality and found that cereal fiber intake had the strongest inverse association with lower all cause (Hazard ratio=0.73; 95% CI, 0.58-0.91) and CVD (HR=0.72; 95% CI, 0.52-0.99) mortality.

In addition, the authors found that on average, women and men in the study increased dietary fiber intake after MI. Those study participants who increased their dietary fiber intake and were in the highest third before and after MI had the lowest all cause mortality (HR=0.73; 95% CI, 0.54-0.99; P=.01 for women and HR:0.81; 95% CI, 0.58-1.13; P=.16 for men).

“Overall, the benefits from increased fiber intake were strongest for fiber from cereal and grain sources,” Li and colleagues reported.

Why beneficial?

A high fiber diet may have a beneficial effect on coronary heart disease and mortality for a number of potential reasons, such as the ability to reduce systemic inflammation, lower serum low-density lipoprotein cholesterol, reduce lipid peroxidation, improve insulin sensitivity, and provide better glycemic control, the authors noted.

A diet high in fiber from regular consumption of whole grains has been shown to reduce the risk of coronary heart disease by up to 40%. However, the authors noted that not even 5% of U.S. population consumes the recommended minimum amount of daily fiber, which is 25 g for women and 38 g for men.

“In our study, the association with all cause mortality was stronger than with cardiovascular mortality,” Li and colleagues noted. “This may occur because patients who have experienced MI are initially and increasingly targeted for intensive medical and therapeutic management to reduce their risk of recurrent cardiovascular events, and less so for the many other causes of death.”

The study was supported by the National Institute of Health.