Allium vegetable intake and gastric cancer : a case-control study and meta-analysis

Scope: To provide new epidemiological data and summarize evidence on the association between allium vegetable intake and gastric cancer risk. Methods and results: Data were from an Italian case-control study including 230 cases and 547 controls. Odds ratios were derived using multiple logistic regression. We combined results from all published studies using random-effect models. In our case-control study, the odds ratios were 0.59 (95% confidence interval, CI, 0.25-1.41) for ≥2 portions of onion per week, 0.69 (95% CI, 0.41-1.15) for high garlic intake, and 0.70 (95% CI, 0.39-1.28) for frequent use of both onion and garlic. Besides our study, 22 case-control and four cohort studies were included in the meta-analyses (>10 000 cases). The pooled relative risks for the highest versus lowest intake category were 0.78 (95% CI, 0.67-0.91) for allium vegetables (ten case-control and four cohort studies), 0.60 (95% CI, 0.47-0.76) for garlic (12 case-control studies), and 0.55 (95% CI, 0.41-0.73) for onion (13 case-control studies). The pooled relative risk for high allium vegetable intake from the four cohorts was 1.02 (95% CI, 0.88-1.18). Conclusion: High allium vegetable consumption is likely to reduce gastric cancer risk. This evidence is derived mainly from case-control studies. Further data from large cohorts are desirable for conclusive confirmation.