Dietary Phytochemical Index and Its Relationship With Diminished Ovarian Reserve: Evidence From a Case–Control Study

INTRODUCTION: Diminished ovarian reserve (DOR) represents a significant contributor to female infertility and adverse reproductive outcomes. Although diet may play a role, the specific impact of phytochemical-rich dietary patterns remains underexplored. So, we aimed to investigate the association between adherence to a dietary phytochemical index (DPI) and the likelihood of DOR among women attending fertility clinics. METHODS: This case-control study enrolled 370 women, comprising 120 individuals diagnosed with DOR and 250 age- and body mass index (BMI)-matched controls with normal ovarian reserve. A validated semi-quantitative food frequency questionnaire (FFQ) was applied to assess dietary intakes and, accordingly, DPI was calculated as the proportion of total energy intake obtained from phytochemical-abundant foods. Antral follicle count (AFC) and serum anti-Müllerian hormone (AMH) measurements were utilized as indicators of ovarian reserve. The association between DPI and the odds of DOR was investigated using multivariable logistic regression models. RESULTS: Our findings showed that higher DPI was associated with a reduced odds of DOR (Q4 vs. Q1 OR: 0.79; 95% CI: 0.55-0.93; p-trend = 0.010). After adjustment for physical activity and energy intake, the association remained significant (OR: 0.80; 95% CI: 0.54-0.95; p-trend = 0.033). In the fully adjusted model, which included additional adjustments for fat mass and body mass index, women in the highest DPI quartile had 27% lower odds of DOR compared to those in the lowest quartile (OR: 0.73; 95% CI: 0.42-0.97; p-trend = 0.02). Besides, in the control group, AFC differed significantly across DPI quartiles (p < 0.001), with the highest mean in the second quartile. CONCLUSION: Our findings suggest that a phytochemical-rich diet may help reduce the odds of DOR, highlighting the role of diet in reproductive health. However, further prospective studies and mechanistic research are warranted to confirm these results and clarify underlying pathways.