A cross-sectional study of the association between plant-based diet indices and kidney stones among Iranian adults

There are limited studies on the relationship between plant-based diet indices (PDIs) including plant-based diet index (PDI), healthful plant-based diet index (hPDI) and unhealthful plant-based diet index (uPDI) and kidney stones (KS), especially in Middle Eastern populations. We aimed to investigate the relationship between these plant-based diet indices (PDI, hPDI, and uPDI) and KS in a large group of Iranian adults. This cross-sectional study was carried out on 9,839 adult participants aged 35-70 years. Dietary data were collected using a validated semi-quantitative 118-item food frequency questionnaire. The scoring method suggested by Satija et al. was applied to examine the adherence to the PDIs including PDI, hPDI, and uPDI. These indices are grounded in evidence linking plant-based foods to health outcomes such as obesity, diabetes, cancer, and cardiovascular disease. The history of KS was identified based on self-reported information provided by the participants. Approximately 16.4% (n = 1638) of study participants were found to have KS. After adjustment for a wide range of confounding variables, a significant positive association was observed between PDI and KS (OR: 1.17; 95% CI: 1.01-1.37). In the case of hPDI, we found no significant association between hPDI scores and risk of KS after adjustment for potential confounders (OR: 1.16; 95% CI: 0.98-1.38). Non-significant association was also observed for uPDI and risk of KS in the fully adjusted model (OR: 1.14; 95% CI: 0.95-1.35). In conclusion, findings of the present study showed that higher PDI score was positively associated with the risk of KS, whereas the hPDI and uPDI scores were not associated with the risk of KS. Further prospective studies are needed to establish causal relationships.