Background: C-reactive protein (CRP), a sensitive marker of inflammation, is an independent predictor of future cardiovascular disease (CVD), which is a major cause of death worldwide. In epidemiological trials, high-fiber intakes have consistently been associated with reduction in CVD risk and CRP levels.
Objective: The objective of this study was to assess the influence of dietary fiber (DF) on C-reactive protein in clinical trials.
Data sources: Databases were searched from the earliest record to April 2008 and supplemented by crosschecking reference lists of relevant publications.
Study selection: Human adult intervention trials, at least 2 weeks in duration, with an increased and measurable consumption of dietary fiber were included and rated for quality.
Data synthesis: Seven clinical trials were included, and six of these reported significantly lower CRP concentrations of 25% to 54% with increased dietary fiber consumption with dosages ranging between 3.3 and 7.8 g/MJ [grams per megajoule; 1 megajule equaling about 239 calories consumed]. The seventh trial with psyllium fiber supplementation failed to lower CRP levels significantly in overweight/obese individuals.
Weight loss and altered fatty acid intakes were present in most of the studies.
Conclusions: In the presence of weight loss and modified saturated, monounsaturated and polyunsaturated fat intakes, significantly lower CRP concentrations (reductions of 25% to 54%) are seen with increased fiber consumption (>/=3.3 g/MJ).
Mechanisms are inconclusive but may involve the effect of dietary fiber on weight loss, and/or changes in the secretion, turnover or metabolism of insulin, glucose, adiponectin, interleukin-6, free fatty acids and triglycerides.
Clinical studies of high- and low-fiber diets are needed to explore the potential favorable effects as observed epidemiologically, and to understand individual susceptibility to its anti-inflammatory effect and long-term cardiovascular reduction.
Source: European Journal of Clinical Nutrition, Feb 18, 2009. [E-pub in advance] PMID: 19223918, by North CJ, Venter CS, Jerling JC. School of Physiology, Nutrition and Consumer Sciences, North-West University, Potchefstroom, South Africa. [E-mail: