Association between the composite dietary antioxidant index and risk of infertility: Evidence from NHANES 2013-2020 and a Mendelian randomization study.

Objective: The Composite Dietary Antioxidant Index (CDAI) measures the antioxidant capacity of the diet, which is believed to provide protection against various diseases, including depression, osteoporosis, and papillomavirus infection, by neutralizing harmful oxidative stress. However, the relationship between CDAI and infertility is not well understood. This research aims to explore the potential correlations between CDAI and the risk of infertility.

Methods: This research harnessed data from the National Health and Nutrition Examination Survey (NHANES) to execute a cross-sectional analysis involving 8263 US women aged 20-45. Each participant was subjected to two distinct 24-h dietary recall interviews. We calculated the CDAI using average daily antioxidant intake. Infertility was assessed using a standardized questionnaire. The association between CDAI and infertility was examined using weighted multiple logistic regression models, while nonlinear correlations were explored through restricted cubic splines. To affirm the robustness of our findings, sensitivity and subgroup analyses were performed using unweighted logistic regression. Additionally, to ascertain the causal influence of circulating antioxidant levels on infertility, a two-sample univariable Mendelian randomization (MR) analysis was conducted, using the inverse variance weighted (IVW) method as the primary analytic approach.

Results: Participants who were infertile exhibited lower CDAI levels compared to their fertile counterparts. When confounding variables were accounted for in the multivariate weighted logistic regression model, an inverse relationship was observed between CDAI and infertility, with the odds ratio for the highest versus lowest quartile being 0.55 (0.33-0.90, P = 0.02). However, the IVW method indicated that genetically predicted elevated levels of CDAI did not significantly correlate with infertility.

Conclusion: Cross-sectional observational studies indicate that antioxidants from diets might diminish infertility risks. However, findings from MR studies do not confirm a causal connection. Additional prospective research is required to elucidate this association further.