title: Consumption of large amounts of Allium vegetables reduces risk for gastric cancer in a meta-analysis.
abstract: OBJECTIVE
  The chemopreventive effects of Allium vegetables (onions, garlic, shallots, leeks, chives, and so forth) have been studied extensively, although their effect on gastric cancer risk is controversial. We performed a meta-analysis of cohort and case-control studies to analyze this association.
  
  
  METHODS
  We searched MEDLINE for studies of Allium vegetable consumption and gastric cancer that were published in any language, from January 1, 1966, to September 1, 2010. We analyzed 19 case-control and 2 cohort studies, of 543,220 subjects. We pooled the relative risks from individual studies using a random-effects model and performed dose-response, heterogeneity, and publication bias analyses.
  
  
  RESULTS
  In a pooled analysis of all studies, consumption of large amounts of Allium vegetables (in a comparison of the highest and lowest consumption groups) reduced the risk for gastric cancer (odds ratio, 0.54; 95% confidence interval, 0.43-0.65). Specific analyses for onion, garlic, leek, Chinese chive, scallion, garlic stalk, and Welsh onion yielded similar results, except for onion leaf. The estimated summary odds ratio for an increment of 20 g/day of Allium vegetables consumed (approximately the average weight of 1 garlic bulb) was 0.91 (95% confidence interval, 0.88-0.94), based on case-control studies from the dose-response meta-analysis.
  
  
  CONCLUSIONS
  In a meta-analysis, consumption of high levels of Allium vegetables reduced the risk for gastric cancer risk. Because of potential confounding factors and exposure misclassification, further studies are required to establish this association.
authors.affiliation: Department of Gastrointestinal Surgery, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Wen
authors.initials: W
authors.lastname: Zhuang
authors.forename: Wen
authors.initials: W
authors.lastname: Hu
authors.forename: Guan-Jian
authors.initials: GJ
authors.lastname: Liu
authors.forename: Tai-Xiang
authors.initials: TX
authors.lastname: Wu
authors.forename: Xiao-Ting
authors.initials: XT
authors.lastname: Wu
mesh_terms: D000490:Allium; D015986:Confounding Factors, Epidemiologic; D004032:Diet / Q000009:adverse effects; D019317:Evidence-Based Medicine; D006801:Humans; D016017:Odds Ratio; D017594:Publication Bias; D018570:Risk Assessment; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D014675:Vegetables