Objective: To analyze the relationship between onion and garlic intake and benign prostatic hyperplasia (BPH), using data from a multicenter case-control study conducted in Italy.

Methods: A multicenter case-control study of 1369 patients with BPH and 1451 controls, admitted to the same hospitals for a wide spectrum of acute, non-neoplastic conditions, was conducted in Italy between 1991 and 2002. Information was collected by trained interviewers using a validated and reproducible food frequency questionnaire. Multivariate odds ratios (ORs) and 95% confidence intervals (CIs) were obtained after allowance for recognized confounding factors and energy intake.

Results: Compared with nonusers, the multivariate ORs for the highest category of onion and garlic intake were 0.41 (95% CI 0.24 to 0.72) and 0.72 (95% CI 0.57 to 0.91), respectively. The combined OR for frequent users versus nonusers of both onion and garlic was 0.65 (95% CI 0.49 to 0.86). The inverse relationships were consistent across age strata.

Conclusions: This uniquely large data set from European populations showed an inverse association between allium vegetable consumption and BPH.

https://pubmed.ncbi.nlm.nih.gov/17991535/