Vitamin D-plus-calcium supplementation does not appear to significantly cut cancer risk in older women

By Bruce Sylvester

Diet supplementation with vitamin D3 and calcium does not appear to significantly lower risk of cancer in healthy postmenopausal women, researchers reported on March 28, 2017 in JAMA/Journal of the American Medical Association.

The new study was double-blind, placebo-controlled, population-based and randomized clinical.

The investigators randomized 2,303 healthy postmenopausal women 55 years or older to supplement treatment for 4 years (1156) or to placebo for 4 years (1147).  The active treatment subjects received 2000 IU/d of vitamin D3 and 1500 mg/d of calcium. The placebo subjects received identical placebos.

The primary outcome was the comparative incidence of all-type cancer (excluding non-melanoma skin cancers).

The investigators reported a new cancer diagnosis in 109 subjects, 45 (3.89%) in the vitamin D3 + calcium group and 64 (5.58%) in the placebo group, which was not, by using standard statistical analysis, significant ( p =.06).

Adverse events included renal calculi (16 in the vitamin D3 + calcium group and 10 in the placebo group), and elevated serum calcium levels (6 in the vitamin D3 + calcium group and 2 in the placebo group).

“Among healthy postmenopausal older women with a mean baseline serum 25-hydroxyvitamin D level of 32.8 ng/mL, supplementation with vitamin D3 and calcium compared with placebo did not result in a significantly lower risk of all-type cancer at 4 years. Further research is necessary to assess the possible role of vitamin D in cancer prevention,” the authors concluded.

In an accompanying Editorial, the authors noted, “Fortunately, large-scale, general-population, high-dose vitamin D supplementation trials designed to overcome many of the limitations of previous trials are ongoing. The largest of these trials, the Vitamin D and Omega-3 Trial (VITAL; NCT01169259), a 5-year trial of supplemental vitamin D (2000 IU/d) for the primary prevention of cancer and cardiovascular disease in a racially/ethnically diverse cohort of nearly 26,000 men and women across the United States, is expected to provide results soon regarding the role of supplementation for nonskeletal outcomes and the overall balance of benefits and risks. As ongoing large-scale trials report their findings, an improved understanding of these important relationships should come to light.”