Does vitamin D prevent heart attack or cancer?

A new UK study suggests that supplementation with vitamin D or calcium may have no impact on the chances of dying from cancer or vascular disease among seniors with a high risk of bone fractures. The researchers concede, however, that the study has weaknesses.

In the randomized controlled trial, 5,292 people over the age of 70 who had already suffered a bone fracture were divided into four groups: the first group took 800 International Units (IU) of vitamin D daily, the second took 1,000 milligrams of calcium each day, the third group took both supplements, and the fourth group took a placebo for two to five years (1). After up to three years, there were no significant differences in deaths from cancer or heart disease in the four groups.

The researchers commented that the study does not provide the final answer on whether vitamin D can help prevent heart disease or cancer. The dose of vitamin D and the number of participants might not have been high enough, and the study time probably not long enough to show an effect. In addition, the participants often stopped taking their supplements.

Recent research links vitamin D to a wide variety of health benefits. One meta-analysis of observational studies suggested a link between an increased risk of colorectal cancer and low vitamin D status (2). Another meta-analysis of randomized controlled trials suggested that vitamin D supplementation, given mainly for fracture prevention, may reduce all-cause mortality (3). In a large study, low vitamin D status was associated with an increased risk of developing cardiovascular disease (4). Other studies did not find conclusive evidence for such benefits (5, 6).

1. Avenell A. et al. Long-term follow-up for mortality and cancer in a randomized placebo- controlled trial of vitamin D3 and/or calcium (RECORD Trial). Journal of Clinical Endocrinology and Metabolism. Published online December 2011.
2. World Health Organization International Agency for Research on Cancer: Vitamin D and cancer. Working Group Report. 2008. Vol 5. Geneva: World Health Organization.
3. Autier P. andGandini S. Vitamin D supplementation and total mortality. A meta-analysis of randomized controlled trials. Arch Intern Med. 2007; 167:1730–1737.
4. Wang T. J. et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation. 2008; 117:503–511.
5. Freedman D. M. et al. Serum 25-hydroxyvitamin D and cancer mortality in the NHANES III study (1988–2006). Cancer Res. 2010; 70:8587–8597.
6. Cawthon P. M. et al. Osteoporotic Fractures in Men (MrOS) Research Group: Serum 25-hydroxyvitamin D, parathyroid hormone, and mortality in older men. J Clin Endocrinol Metab. 2010; 95:4625–4634.