Vitamin D Fails To Reduce Cancer Risk in Postmenopausal Women

Supplementation with vitamin D₃ and calcium did not significantly reduce the risk of cancer among postmenopausal women, according to a randomized, controlled study published in JAMA.¹

Some studies showed an inverse relationship between vitamin D levels and cancer risk. The purpose of this trial was to evaluate the effect of vitamin D₃ supplementation on cancer risk.

This trial randomly assigned 2303 postmenopausal women to receive 2000 IU of vitamin D₃ and 1500 mg of calcium per day or placebo for 4 years, with follow-up up visits every 6 months.

At baseline, the mean age was 65, 99% were non-Hispanic Caucasian, and the mean serum 25-hydroxyvitamin D level was 33 ng/mL.

The mean serum 25-hydroxyvitamin D levels rose to 43.9 ng/mL by 12 months and was maintained during the 4-year study. In the placebo group, the mean serum 25-hydroxyvitamin D level remained around 31 ng/mL throughout the study.

At 4 years, 3.89% of women in the vitamin D₃ group and 5.58% in the placebo group were diagnosed with cancer (difference, 1.69%; 95% CI, -0.06-3.46%; P = .06), resulting in an incidence of 0.042 (95% CI, 0.032-0.056) and 0.06 (95% CI, 0.048-0.076; P = .06), respectively.

Vitamin D supplementation was not associated with reduced cancer risk with a hazard ratio of 0.70 (95% CI, 0.47-1.02). The lack of association may be a result of the higher baseline serum levels of 25-hydroxyvitamin D compared with the general US population, according to the authors.

The data from this study suggest that vitamin D₃ and calcium supplementation does not reduce the risk of cancer among postmenopausal women, though the authors wrote that “further research is necessary to assess the possible role of vitamin D in cancer prevention.”

Reference

1. Lappe J, Watson P, Travers-Gutafson, et al. Effect of vitamin D and calcium supplementation on cancer incidence in older women. A randomized clinical trial. JAMA. 2017 Mar 28. doi: 10.1001/jama.2017.2115 [Epub ahead of print]