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Cancer risk in older women reduced 32 percent by 2,000 IU of Vitamin D plus Calcium – 4 year RCT Oct 2016

Vitamin D3 and calcium supplementation significantly decreases cancer risk in older women

American Public Health Association 2016 meeting Oct 31, 2016
Joan Lappe, Creighton University; Dianne Travers-Gustafson, Creighton University; Cedric Garland, University of California at San Diego; Robert Heaney, Creighton University; Robert Recker, Creighton University; Patrice Watson, Creighton University

Background/Purpose Strategies to help prevent cancer are sorely needed. A large body of epidemiological evidence links low vitamin D status to increased cancer risk. Further, underlying mechanisms of a vitamin D anticancer effect have been identified. We report here the first randomized clinical trial (RCT) of vitamin D supplementation analyzing cancer as a primary outcome. The study purpose was to determine the efficacy of vitamin D3 plus calcium supplementation in reducing risk of all non-skin cancers combined.

Methods This was a 4-year, double-blind, placebo-controlled RCT in a 31-county rural area. The subjects were a population-based sample of 2,302 healthy postmenopausal women 55 and older. Study groups were: 1) vitamin D3 (2000 IU/d) and calcium (1500 mg/d), or 2) vitamin D3 and calcium placebos. The primary outcome was all types of non-skin cancer combined.

Results/Outcomes 2064 subjects (90%) completed 4 years of study. Baseline serum 25(OH)D was 32.8±10.5 ng/mL. After one year of treatment, 25(OH)D in the group that received vitamin D and calcium increased to 43.9 ng/mL, while it was 31.6 ng/mL in the placebo group. During follow-up, 106 subjects (43 cases, 63 controls) developed at least one invasive or in situ cancer, confirmed by pathology reports. The effect of treatment group (placebo vs vitamin D/calcium) on incidence of cancer was evaluated using Kaplan-Meier survival analysis and proportional hazards regression. Time to first cancer diagnosis was modeled as a function of treatment group. Cancer incidence was lower in women who received vitamin D/calcium than in those who received the placebo (HR = 0.68, 95% CI = 0.46-0.99; P < 0.05).
When analysis was confined to cancers diagnosed after the first year, the HR for the group who received vitamin D/calcium was 0.65 (95% CI = 0.42 to 0.99; P <0.05). In proportional hazards modeling, both treatment group and serum 25(OH)D concentration after one year of intervention were significant predictors of cancer risk.

Conclusions Supplementing with 2000 IU/day of vitamin D3 and 1500 mg/day of calcium substantially reduced risk of all cancers combined. This finding provides great impetus for improving vitamin D status through advances in vitamin D nutritional policy.

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