Effect of Physical Activity on the Association Between Dietary Fiber and Constipation: Evidence From the National Health and Nutrition Examination Survey 2005-2010

Background/Aims The effect of physical activity on the relationship between dietary fiber intake and constipation has not been comprehensively studied. This study aims to explore the impact of physical activity. Methods Data were obtained from 3 cycles of the National Health and Nutrition Examination Survey (NHANES) 2005-2010 and included a total of 13 941 participants aged >= 20 years. Multiple logistic regression analysis was used to investigate the independent association between dietary fiber and constipation. Interaction analysis was also performed to analyze the relationship between dietary fiber and constipation in different physical activity groups. Results Among non-active participants, dietary fiber intake did not associate with stool consistency (OR, 1.02; 95% CI, 0.98-1.05; P = 0.407). For physically active participants, 1-gram unit increase in dietary fiber intake reduced the risk of stool consistency by 3% (OR, 0.97; 95% CI, 0.94-0.99; P = 0.020). Moreover, the relationship between dietary fiber intake and stool consistency was significantly different for groups with different levels of physical activity (P interaction = 0.044). However, dietary fiber intake was not related to stool frequency among non-active participants (OR, 0.99; 95% CI, 0.94-1.05; P = 0.767) nor physically active participants (OR, 1.01; 95% CI, 0.97-1.04; P = 0.751). Conclusions Increasing dietary fiber intake was associated with stool consistency-related constipation among physically active participants, but not among non-active participants. However, increasing dietary fiber intake is not significantly associated with stool frequency in different physical activity groups.