Monthly High-Dose Vitamin D and Cancer Risk


Key Points

  • High-dose monthly vitamin D supplementation without calcium was not associated with a reduced risk of cancer.
  • No reduction in cancer risk was observed in men or women.

In a study reported in JAMA Oncology, Scragg et al found that monthly high-dose vitamin D supplementation, without calcium, was not associated with a reduced risk of developing cancer.

Study Details

The current analysis is a post hoc analysis of the Vitamin D Assessment (ViDA) study, which assessed the effect of vitamin D supplementation on the incidence of cardiovascular disease. In the double-blind study, 5,110 participants (aged 50 to 84 years) from family practices and community groups in Auckland were randomized between April 2011 and November 2012 to receive vitamin D3 (n = 2,558) or placebo (n = 2,552). Oral vitamin D3 was given in an initial bolus dose of 200,000 IU followed by monthly doses of 100,000 IU, with study treatment continuing for a median of 3.3 years (range = 2.5–4.2 years). Study medication was discontinued in July 2015, and follow-up was completed in December 2015. The post hoc primary outcome was the number of all primary invasive and in situ malignant neoplasms (excluding nonmelanoma skin cancers). Participants had a mean age of 65.9 years, 58% were male, and 83% were of European or another race/ethnicity (96% European ancestry), with the remainder being Polynesian or South Asian.

Cancer Outcomes

At baseline, the mean deseasonalized 25-hydroxyvitamin D (25[OH]D) concentration was 26.5 ng/mL. In a random sample of 438 participants, the mean 25(OH)D concentration during follow-up was consistently > 20 ng/mL higher in the vitamin D group than in the placebo group. A total of 328 cancers were reported, with the most common being melanoma in situ (n = 71) and malignant melanoma (n = 55), followed by prostate (n = 64), colorectal (n = 38), breast (n = 36), and lymphoid and hematopoietic cancers (n = 36).

Cancers occurred in 165 participants (6.5%) in the vitamin D group vs 163 (6.4%) in the placebo group (hazard ratio [HR] = 1.01, P = .95). Results were similar in men (HR = 0.96, 95% CI = 0.74–1.25) and women (HR = 1.09, 95% CI = 0.75–1.59) in the 2 groups, as well as in participants with 25(OH)D < 20 ng/mL (HR = 1.01, 95% CI = 0.65–1.58) or ≥ 20 ng/mL (HR = 1.04, 95% CI = 0.81–1.33).

The investigators concluded, “High-dose vitamin D supplementation prescribed monthly for up to 4 years without calcium may not prevent cancer. This study suggests that daily or weekly dosing for a longer period may require further study.”

The study was funded by the Health Research Council of New Zealand and Accident Compensation Corporation of New Zealand.

Robert Scragg, MBBS, PhD, of the School of Population Health, University of Auckland, is the corresponding author of the JAMA Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.