Increasing Fiber in Western Diet Could Help Prevent Hypertension
Clinical studies of the blood pressure-lowering effect of dietary fiber supplementation have produced varying results. Now, a meta-analysis of data from 24 trials of fiber supplementation has concluded that this dietary modification has a small blood pressure-lowering effect and that increasing fiber in the general population could contribute to the prevention of hypertension.
Researchers from Wageningen University in The Netherlands identified randomized, placebo-controlled trials published between January 1, 1966, and January 1, 2003. A total of 1404 subjects took part in the trials, which lasted for a mean of 9 weeks. The mean age of the trial participants was 42 years, and their average baseline blood pressure was 133/82 mm Hg. Fiber intake was increased in 4 of the trials by dietary supplementation and in the remaining 20 trials by administration of soluble or insoluble fiber or a mixture of both. Fiber doses varied between 3.5 g and 42.6 g per day; average dose was 11.5 per day.
The overall effect of fiber supplementation in these 24 trials was calculated to be:
An average decrease of 1.13 mm Hg in SBP (nonsignificant)
An average decrease of 1.26 mm Hg in DBP (significant).
The blood pressure reductions were greater in populations with a mean age > 40 years than in those aged ≤ 40 years, but only significantly greater for SBP. Significantly greater reductions in blood pressure were seen in the hypertensive populations (in 8 trials) than in the normotensive populations, but this difference became nonsignificant after adjustment for the older age of the hypertensive populations (52 years vs 37 years for the normotensive populations). Changes in blood pressure were not related to duration of intervention, and they became less marked with increasing fiber dose. There was some evidence that water-soluble fiber had a greater blood pressure effect than insoluble fiber.
In their report, in the January 24 issue of Archives of Internal Medicine , lead researcher Johanna M. Geleijnse, PhD, and colleagues note that daily intake of fiber in Western countries is low, at about 15 g, despite recommendations that it should be between 25 g and 30 g. They also note that increasing dietary fiber intake could have other cardiovascular benefits, such as reducing LDL-cholesterol, and suggest that given the large segment of the population with inadequate fiber intake, demonstration of these beneficial effects could impact public health policy.
Medscape Cardiology. 2005;9(1) © 2005 Medscape
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