Dietary Fiber, C-Reactive Protein, and Leisure-Time Physical Activity among U.S. Adults

Background: Some evidence suggests an inverse association between increased fiber intake and C-reactive protein (CRP). However, few studies have examined the associations among CRP, dietary fiber, and leisure-time physical activity (LTPA) in a nationally representative sample of U.S. adults. Methods: Sample (n = 8372) included adults (≥20 years of age) who participated in the 2007-2010 National Health and Nutrition Examination Survey. Tertiles of reported fiber intake were created. The dependent variable was elevated CRP (>3-10 mg/L). Logistic regression models were stratified by LTPA participation and adjusted for age, gender, race, waist circumference (WC), and standing height. Results: In adults reporting any volume of LTPA participation, increased fiber intake was significantly (P < 0.05 for the upper tertile of fiber intake) associated with lower odds of having an elevated CRP concentration when compared with the lowest tertile. Similar associations were not revealed in analyses limited to adults reporting no LTPA participation. After additional adjustment for WC and standing height, this protective association was no longer statistically significant. Conclusions: Results suggest that WC and standing height may mediate the beneficial association between increased fiber intake and lower odds of elevated CRP in adults reporting LTPA participation.