title: Magnesium intake, plasma C-peptide, and colorectal cancer incidence in US women: a 28-year follow-up study.
abstract: BACKGROUND
  Laboratory studies suggest a possible role of magnesium intake in colorectal carcinogenesis but epidemiological evidence is inconclusive.
  
  
  METHODS
  We tested magnesium-colorectal cancer hypothesis in the Nurses' Health Study, in which 85 924 women free of cancer in 1980 were followed until June 2008. Cox proportional hazards regression models were used to estimate multivariable relative risks (MV RRs, 95% confidence intervals).
  
  
  RESULTS
  In the age-adjusted model, magnesium intake was significantly inversely associated with colorectal cancer risk; the RRs from lowest to highest decile of total magnesium intake were 1.0 (ref), 0.93, 0.81, 0.72, 0.74, 0.77, 0.72, 0.75, 0.80, and 0.67 (P(trend)<0.001). However, in the MV model adjusted for known dietary and non-dietary risk factors for colorectal cancer, the association was significantly attenuated; the MV RRs were 1.0 (ref), 0.96, 0.85, 0.78, 0.82, 0.86, 0.84, 0.91, 1.02, and 0.93 (P(trend)=0.77). Similarly, magnesium intakes were significantly inversely associated with concentrations of plasma C-peptide in age-adjusted model (P(trend)=0.002) but not in multivariate-adjusted model (P(trend)=0.61). Results did not differ by subsite or modified by calcium intakes or body mass index.
  
  
  CONCLUSIONS
  These prospective results do not support an independent association of magnesium intake with either colorectal cancer risk or plasma C-peptide levels in women.
authors.affiliation: Department of Medicine, Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School, 401 Park Drive, Boston, MA 02115, USA. xuehong.zhang@channing.harvard.edu
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: E L
authors.initials: EL
authors.lastname: Giovannucci
authors.forename: K
authors.initials: K
authors.lastname: Wu
authors.forename: S A
authors.initials: SA
authors.lastname: Smith-Warner
authors.forename: C S
authors.initials: CS
authors.lastname: Fuchs
authors.forename: M
authors.initials: M
authors.lastname: Pollak
authors.forename: W C
authors.initials: WC
authors.lastname: Willett
authors.forename: J
authors.initials: J
authors.lastname: Ma
mesh_terms: D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood*; D002118:Calcium; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D004032:Diet; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D008274:Magnesium; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
chemical_list: D002096:C-Peptide; D007328:Insulin; D008274:Magnesium; D002118:Calcium