Effect of a high-fiber diet vs a fiber supplemented diet on C-reactive protein level.

A growing body of evidence has shown that inflammation plays a significant role in the development of cardiovascular disease (CVD).  Elevated levels of C-reactive protein (CRP), a key marker of inflammation, has been linked to insulin resistance, hypertension, development of diabetes, metabolic syndrome, as well as other CVD risk factors.  Results from epidemiologic studies have shown that diet may play an integral role in lowering markers of inflammation.  In particular, dietary fiber has been suggested to favorably impact levels of CRP and other inflammatory markers.  The objective of the present study was to investigate the effects of a diet naturally high in dietary fiber, as well as a diet supplemented with dietary fiber (psyllium), on markers of inflammation including CRP. 

Thirty-five individuals (women = 28; men = 7) aged 18-49 years participated in this randomized crossover intervention trial.  Participants included 18 lean normotensive, and 17 obese hypertensive men and women.   The two intervention diets included a diet naturally high in dietary fiber (30g/d; the Dietary Approaches to Stop Hypertension (DASH)), and a diet supplemented with psyllium.  Each diet was designed to reach 30g/d of dietary fiber.  Experimental diets were randomized in a 2-period crossover design.  Caloric composition of both diets were planned and regulated to supply 50% carbohydrate, 34% fat, and 16% protein.  In the supplemented group, psyllium was added to the usual diet to match the naturally high fiber DASH diet.   Participants were first evaluated while consuming their usual diets, and again following randomization to the experimental diets.  To ensure dietary compliance, participants were required to photograph all food and beverages consumed for 3 days each week of each 3-week dietary period.  Serum samples were obtained at baseline, and at the end of each dietary period for subsequent analysis of inflammatory markers. 

The mean fiber intake in the baseline diet was 11.9g/d.  Mean fiber intake for the DASH diet was 27.7g, and 26.6g for the psyllium supplement diet. CRP levels decreased from 4.4mg/L at baseline to 3.8mg/L (-13.7%) following the DASH diet, and to 3.6mg/L (-18.1%) in the pysillium supplemented group. A reduction in CRP levels was observed for the 18 lean normotensive participants, with no significant change in CRP observed in the obese hypertensive individuals.  Weight, triglyceride levels, cholesterol level, and insulin resistance status did not change in either intervention groups. Diets high in fiber (both naturally occurring and supplemented) appear to be effective in reducing levels of inflammation.