Association between dietary inflammatory index and polycystic ovary syndrome: a meta-analysis of case-control studies
TL;DR
Existing evidence supports DII as a potential tool for estimating PCOS status associated with diet, and the small effect size observed in this study indicates a significant association between DII and PCOS.
Abstract
Objective This study aimed to systematically analyze the association of the dietary inflammatory index (DII) with polycystic ovary syndrome (PCOS) status, thus offering evidence-based support for dietary interventions in the management of PCOS. Methods Four databases were systematically searched to collect case-control studies on DII and PCOS published up to December 21, 2025. The Newcastle-Ottawa Scale (NOS) was utilized to assess the risk of bias in the included studies. Using Stata 15.0, we conducted a meta-analysis to compare DII scores in PCOS patients versus those in healthy controls. Subgroup analyses were conducted to identify sources of heterogeneity. An exploratory meta-regression was conducted, but due to the small number of studies, the results could not be interpreted. Results Six case-control studies involving 1,554 participants were ultimately included. Meta-analysis revealed slightly but statistically significantly higher DII scores in the PCOS group than in healthy controls (standardized mean difference [SMD]: 0.23; 95% confidence interval [CI]: 0.06–0.40; P = 0.008). Sensitivity analyses suggested robustness of the results. Egger’s test showed no statistical evidence of publication bias (P = 0.611); however, with only six studies the statistical power was very low, so publication bias cannot be excluded, and this analysis should be regarded as exploratory. Conclusion Pro-inflammatory dietary patterns are modestly associated with PCOS. Although causality inference is impossible due to the design of included studies, existing evidence supports DII as a potential tool for estimating PCOS status associated with diet. The small effect size observed in this study indicates a significant association between DII and PCOS. However, statistical association does not necessarily imply practical clinical relevance, and further studies are warranted to replicate and validate this relationship. Systematic Review Registration https://www.crd.york.ac.uk/PROSPERO/view/1239576, identifier CRD420251239576.