title: Prediagnostic plasma vitamin C and risk of gastric adenocarcinoma and esophageal squamous cell carcinoma in a Chinese population.
abstract: BACKGROUND
  China has some of the highest incidence rates for gastric adenocarcinoma (GA) and esophageal squamous cell carcinoma (ESCC) in the world. Prospective studies suggested that vitamin C may reduce risks; however, associations are unclear because of limited sample size.
  
  
  OBJECTIVE
  The objective was to examine the relation between prediagnostic plasma vitamin C and the risk of GA and ESCC.
  
  
  METHODS
  A case-cohort study was used to assess the association between prediagnostic plasma vitamin C and incidence of GA (n = 467) and ESCC (n = 618) in the General Population Nutrition Intervention Trial. With the use of multivariate Cox proportional hazards models, we estimated the HRs and 95% CIs. We also conducted a meta-analysis of the literature up to 1 October 2012 on the relation between circulating vitamin C and gastric cancer incidence. Two cohort studies and the current study were included to assess the body of evidence.
  
  
  RESULTS
  For GA, each 20-μmol/L increase in plasma vitamin C was associated with a 14% decrease in risk (HR: 0.86; 95% CI: 0.76, 0.96). Compared with individuals with low plasma vitamin C concentrations (≤28 μmol/L), those with normal concentrations (>28 μmol/L) had a 27% reduced risk of GA (HR: 0.73; 95% CI: 0.56, 0.94). No association between vitamin C concentrations and ESCC was seen. Meta-analysis showed that the risk of incident GA among those with the highest concentration of plasma vitamin C was 31% lower (random-effects-pooled-odds ratio 0.69; 95% CI: 0.54, 0.89) than those in the lowest category.
  
  
  CONCLUSIONS
  Our data provide evidence that higher circulating vitamin C was associated with a reduced risk of incident GA, but no association was seen for ESCC.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Genetic Epidemiology Branch (TKL and PRT), Nutritional Epidemiology Branch (NDF, SMD, and CCA), and the Division of Cancer Control and Population Sciences, Epidemiology and Genomics Research Program (TKL), Rockville, MD; and the Cancer Institute, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People's Republic of China (J-HF and Y-LQ).
authors.forename: Tram Kim
authors.initials: TK
authors.lastname: Lam
authors.forename: Neal D
authors.initials: ND
authors.lastname: Freedman
authors.forename: Jin-Hu
authors.initials: JH
authors.lastname: Fan
authors.forename: You-Lin
authors.initials: YL
authors.lastname: Qiao
authors.forename: Sanford M
authors.initials: SM
authors.lastname: Dawsey
authors.forename: Philip R
authors.initials: PR
authors.lastname: Taylor
authors.forename: Christian C
authors.initials: CC
authors.lastname: Abnet
mesh_terms: D001205:Ascorbic Acid / Q000008:administration & dosage / Q000097:blood*; D044466:Asian People; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology* / Q000517:prevention & control; D002681:China / Q000453:epidemiology; D004938:Esophageal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D000077277:Esophageal Squamous Cell Carcinoma; D006801:Humans; D015994:Incidence; D016017:Odds Ratio; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000453:epidemiology* / Q000517:prevention & control
chemical_list: D001205:Ascorbic Acid
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