Effect of dietary fiber intake on blood pressure: a meta-analysis of randomized, controlled clinical trials.

OBJECTIVE We conducted a meta-analysis of 25 randomized controlled trials published in English-language journals before February 2004, to assess the effect of dietary fiber intake on blood pressure (BP). DESIGN Using a standardized protocol, information on study design, sample size, participant characteristics, duration of follow-up and change in mean BP, was abstracted. The data from each study were pooled using a random effects model to provide an overall estimate of dietary fiber intake on BP. INTERVENTION Dietary fiber intake was the only significant intervention difference between the active and control groups. RESULTS Overall, dietary fiber intake was associated with a significant -1.65 mmHg [95% confidence interval (CI), -2.70 to -0.61] reduction in diastolic BP (DBP) and a non-significant -1.15 mmHg (95% CI, -2.68 to 0.39) reduction in systolic BP (SBP). A significant reduction in both SBP and DBP was observed in trials conducted among patients with hypertension (SBP -5.95 mmHg, 95% CI, -9.50 to -2.40; DBP -4.20 mmHg, 95% CI, -6.55 to -1.85) and in trials with a duration of intervention > or = 8 weeks (SBP -3.12 mmHg, 95% CI, -5.68 to -0.56; DBP -2.57 mmHg, 95% CI, -4.01 to -1.14). CONCLUSIONS Our results indicate that increased intake of dietary fiber may reduce BP in patients with hypertension and suggests a smaller, non-conclusive, reduction in normotensives. An intervention period of at least 8 weeks may be necessary to achieve the maximum reduction in BP. Our findings warrant conduct of additional clinical trials with a larger sample size and longer period of intervention to examine the effect of dietary fiber intake on BP.