title: Dietary intake of flavonoid subclasses and risk of colorectal cancer: evidence from population studies.
abstract: OBJECTIVE
  To systematically evaluate the relationship between flavonoids intake and colorectal cancer risk by conducting a meta-analysis.
  
  
  RESULTS
  Our meta-analysis included 18 studies involving 16,917 colorectal cancer cases in 559,486 participants in relations to flavonoids intake during six to twenty-six years of follow-up. Our results indicated that specific flavonoid subclasses, such as procyanidins (OR = 0.75; 95% CI, 0.66-0.86) and isoflavones (OR = 0.87; 95% CI, 0.78-0.98), showed protective effects against colorectal cancer risk. There was no enough evidence indicating that increased consumption of total flavonoids were significantly associated with reduced risk of colorectal cancer (OR = 0.94, 95% CI, 0.81-1.09). There was no publication bias across studies.
  
  
  METHODS
  We performed a systematic search of PubMed, Web of Science and the Cochrane Library databases for relevant articles before December 2015. A random-effects model was used to estimate summary odds ratios and 95% confidence intervals (CIs) for associations between flavonoids and colorectal cancer risk. We assessed heterogeneity among studies by the Cochran Q and I2 statistics.
  
  
  CONCLUSIONS
  Our meta-analysis provides comprehensive evidence and partly supported the hypothesis that higher habitual intake of foods rich in procyanidins and isoflavones may potentially decrease colorectal cancer incidence. More prospective studies are warranted to verify this protective association.
authors.affiliation: Department of Gastroenterology, Sir Run Run Shaw Hospital, Zhejiang University Medical School, Hangzhou 310016, China.|Institute of Gastroenterology, Zhejiang University (IGZJU), Hangzhou 310016, China.
authors.forename: Xingkang
authors.initials: X
authors.lastname: He
authors.affiliation: Department of Gastroenterology, Sir Run Run Shaw Hospital, Zhejiang University Medical School, Hangzhou 310016, China.|Institute of Gastroenterology, Zhejiang University (IGZJU), Hangzhou 310016, China.
authors.forename: Lei-Min
authors.initials: LM
authors.lastname: Sun
mesh_terms: D015179:Colorectal Neoplasms / Q000453:epidemiology*; D004032:Diet; D005419:Flavonoids; D006801:Humans; D012307:Risk Factors
chemical_list: D005419:Flavonoids
keywords: colorectal cancer; flavonoids; isoflavones; procyanidins