title: Serum 25-Hydroxyvitamin D Concentrations ≥40 ng/ml Are Associated with >65% Lower Cancer Risk: Pooled Analysis of Randomized Trial and Prospective Cohort Study.
abstract: BACKGROUND
  Higher serum 25-hydroxyvitamin D [25(OH)D] concentrations have been associated with a lower risk of multiple cancer types across a range of 25(OH)D concentrations.
  
  
  OBJECTIVE
  To investigate whether the previously reported inverse association between 25(OH)D and cancer risk could be replicated, and if a 25(OH)D response region could be identified among women aged 55 years and older across a broad range of 25(OH)D concentrations.
  
  
  METHODS
  Data from two cohorts representing different median 25(OH)D concentrations were pooled to afford a broader range of 25(OH)D concentrations than either cohort alone: the Lappe cohort (N = 1,169), a randomized clinical trial cohort (median 25(OH)D = 30 ng/ml) and the GrassrootsHealth cohort (N = 1,135), a prospective cohort (median 25(OH)D = 48 ng/ml). Cancer incidence over a multi-year period (median: 3.9 years) was compared according to 25(OH)D concentration. Kaplan-Meier plots were developed and the association between 25(OH)D and cancer risk was examined with multivariate Cox regression using multiple 25(OH)D measurements and spline functions. The study included all invasive cancers excluding skin cancer.
  
  
  RESULTS
  Age-adjusted cancer incidence across the combined cohort (N = 2,304) was 840 cases per 100,000 person-years (1,020 per 100,000 person-years in the Lappe cohort and 722 per 100,000 person-years in the GrassrootsHealth cohort). Incidence was lower at higher concentrations of 25(OH)D. Women with 25(OH)D concentrations ≥40 ng/ml had a 67% lower risk of cancer than women with concentrations <20 ng/ml (HR = 0.33, 95% CI = 0.12-0.90).
  
  
  CONCLUSIONS
  25(OH)D concentrations ≥40 ng/ml were associated with substantial reduction in risk of all invasive cancers combined.
authors.affiliation: GrassrootsHealth, Encinitas, California, United States of America.
authors.forename: Sharon L
authors.initials: SL
authors.lastname: McDonnell
authors.affiliation: GrassrootsHealth, Encinitas, California, United States of America.
authors.forename: Carole
authors.initials: C
authors.lastname: Baggerly
authors.affiliation: GrassrootsHealth, Encinitas, California, United States of America.
authors.forename: Christine B
authors.initials: CB
authors.lastname: French
authors.affiliation: GrassrootsHealth, Encinitas, California, United States of America.
authors.forename: Leo L
authors.initials: LL
authors.lastname: Baggerly
authors.affiliation: Department of Family Medicine and Public Health, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Cedric F
authors.initials: CF
authors.lastname: Garland
authors.affiliation: Department of Family Medicine and Public Health, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Gorham
authors.affiliation: Department of Medicine, Creighton University, Omaha, Nebraska, United States of America.
authors.forename: Joan M
authors.initials: JM
authors.lastname: Lappe
authors.affiliation: Department of Medicine, Creighton University, Omaha, Nebraska, United States of America.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Heaney
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009369:Neoplasms / Q000097:blood / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D