Association between dietary protein intake and constipation: Data from the National Health and nutrition examination survey 2005-2010.

Background: The association between dietary protein intake and constipation remains inconclusive. The aim of this study was to investigate whether dietary protein intake is associated with constipation.

Methods: This cross-sectional study included 13,941 adults from the 2005 to 2010 National Health and Nutrition Examination Survey. A weighted logistic regression analysis was used to control for confounding factors. In addition, weighted interaction and stratified analyses were conducted to ascertain the potential modifying factors.

Results: The prevalence of constipation was 7.5% when constipation was defined by stool consistency and 3.5% when constipation was defined by stool frequency. After adjusting for covariates, an increase in dietary protein intake of 10 g was not associated with constipation, as defined by stool frequency (OR = 0.94, 95% CI = 0.54, 1.62) or stool consistency (OR = 1.02, 95% CI = 0.75, 1.39). Subgroup analyses revealed that dietary protein intake was associated with an increase in constipation defined by stool consistency risk in participants who consumed a low amount of carbohydrates (OR = 1.08, 95% CI = 1.02-1.14 for every 10-g increase in protein intake), but a decrease in risk in participants in the moderate-carbohydrate group (OR = 0.94, 95% CI = 0.89-0.99 for every 10-g increase in protein intake), suggesting a significant interaction (p = 0.001).

Conclusion & Inferences: Dietary protein intake is not associated with stool consistency or frequency-defined constipation. However, the association between dietary protein intake and constipation defined by stool consistency in participants with a low carbohydrate intake differed from that in participants with a moderate carbohydrate intake.