title: Colorectal cancer and adenomatous polyps in relation to allium vegetables intake: a meta-analysis of observational studies.
abstract: METHODS
  To provide updated quantitative estimates of the associations between allium vegetables intake and risk of colorectal cancer and colorectal adenomatous polyps.
  
  
  RESULTS
  We combined all published data on the issue, using a meta-analytic approach. Pooled relative risks (RRs) were calculated using random-effects models. Sixteen studies (13 333 cases) were included in the meta-analyses of colorectal cancer. Seven studies provided information on garlic, six on onion, and four on total allium vegetables. The pooled RRs of colorectal cancer for the highest versus the lowest category of intake were 0.85 (95% confidence interval; CI, 0.72-1.00) for garlic (0.76 for case-control, 0.99 for cohort studies), 0.85 (95% CI, 0.70-1.04) for onion (0.74 for case-control, 1.04 for cohort studies), and 0.78 (95% CI, 0.56-1.08) for total allium vegetables. Significant heterogeneity was found for the three meta-analyses. The pooled RR of colorectal adenomatous polyps for the highest versus the lowest category of total allium vegetables intake was 0.88 (95% CI, 0.80-0.98, three studies), with no heterogeneity.
  
  
  CONCLUSIONS
  High garlic intake may reduce the risk of colorectal cancer. However, evidence of such protection derived mainly from case-control studies. High intake of total allium vegetables may be associated with a risk reduction of colorectal adenomatous polyps.
authors: Department of Epidemiology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors: Federica
authors: F
authors: Turati
authors: Valentina
authors: V
authors: Guercio
authors: Claudio
authors: C
authors: Pelucchi
authors: Carlo
authors: C
authors: La Vecchia
authors: Carlotta
authors: C
authors: Galeone
mesh_terms: D018256:Adenomatous Polyps / Q000517:prevention & control*; D000490:Allium; D015179:Colorectal Neoplasms / Q000517:prevention & control*; D004032:Diet; D006801:Humans; D064887:Observational Studies as Topic; D014675:Vegetables
keywords: Allium vegetables; Colorectal adenomatous polyps; Colorectal neoplasm; Diet; Garlic