L-shaped association of dietary inflammatory index (DII) and chronic diarrhea: results from NHANES 2005-2010

Background: Since diet is a known modulator of inflammation, the Dietary Inflammatory Index (DII), which quantifies the inflammatory potential of an individual's diet, becomes a significant parameter to consider. Chronic diarrhea is commonly linked to inflammatory processes within the gut. Thus, this study aimed to explore the potential link between DII and chronic diarrhea.

Methods: This research utilized data from the National Health and Nutrition Examination Survey (NHANES) 2005-2010. The DII was calculated according to the average intake of 28 nutrients using information gathered from two 24-hour recall interviews. The Bristol Stool Form Scale (BSFS) was adopted to describe chronic diarrhea, identifying stool Type 6 and Type 7. Multivariate logistic regression models examined the causal connection between DII and chronic diarrhea. Additionally, subgroup analyses and interaction tests were conducted.

Results: The study encompassed 11,219 adults, among whom 7.45% reported chronic diarrhea. Initially, multivariate logistic regression analysis revealed a positive association between DII and chronic diarrhea. Nevertheless, this connection lost statistical significance (OR = 1.00; 95% CI, 0.96-1.05; P = 0.8501) after adjusting for all confounding variables. Stratified by sex, the analysis revealed a notable rise in the risk of chronic diarrhea with increasing DII among female participants (all P for trend < 0.05). This tendency remained constant even after full adjustment (P for trend = 0.0192), whereas no significant association was noted in males (all P for trend > 0.05). Furthermore, an L-shaped association emerged between DII and chronic diarrhea, with an inflection point of -1.34. In the population with DII scores below -1.34, each unit increase in DII correlated with a 27% reduction in the probability of chronic diarrhea (OR = 0.73; 95% CI, 0.57-0.93), whereas in the population with DII scores above -1.34, the risk increased by 4% (OR = 1.04; 95% CI, 0.98-1.10). Merely, the gender interaction was shown to be statistically significant based on subgroup analyses and interaction tests.

Conclusions: A favorable association between DII and chronic diarrhea exists in adults in the United States. Nevertheless, additional long-term prospective studies are required to confirm and solidify those findings.