Tag Archives: Calcium

Yet Another Null Result on Vitamin D and Calcium Supplementation in Older Women

Hard on the heels of the results of a systematic review in a recent blog,[1] yet another RCT of calcium and vitamin D in healthy people.[2] This time the end-point is cancer, and again the result is null. The authors call for yet more research but, again, one wonders whether this topic should not just be put to bed. It is true, of course, that exposure to sunlight is associated with lower risk of cancer, but this might not be a causal relationship, and even if it is, sunlight and oral vitamin D are not the same thing, just as oral and ovarian oestrogen are not equivalent.

— Richard Lilford, CLAHRC WM Director

References:

  1. Lilford RJ. Effects of Vitamin D Supplementation. NIHR CLAHRC West Midlands News Blog. 24 March 2017.
  2. Lappe J, Watson P, Travers-Gustafson D, et al. Effect of Vitamin D and Calcium Supplementation on Cancer Incidence in Older Women. A Randomized Clinical Trial. JAMA. 2017; 317(12): 1234-43.

Effects of Vitamin D Supplements

Bolland and colleagues have written a lovely summary of the evidence on the effects of vitamin D supplements, with or without calcium, on health.[1] Their careful and comprehensive systematic overview based on a large sample, and providing narrow confidence limits, finds that there is no evidence that vitamin D, with or without calcium, reduces the risk of fractures in elderly people with no known bone disease. It is, as expected, efficacious in people with established osteomalacia. Systematic reviews of lower quality or based on per protocol analyses, tend to find the more optimistic results, but the data, taken in the round, yield a null result. The reviewers find that additional research is unlikely to further clarify the issue, as an effect of more than a 10% reduction in fracture has been ‘excluded’ by the existing studies. From a Bayesian perspective, further data are unlikely to have much effect on credible limits. The studies do not find any evidence that calcium plus vitamin D have either harmful or beneficial effects on the other (non-skeletal) outcomes, such as cancer or heart disease. Perhaps this is an example of the horizon of science; science cannot prove a null result, merely exclude a positive or negative effect beyond certain limits. We will never know everything, but let’s just forget about the use of vitamin D and calcium as prophylaxis in healthy people as any benefit must be nugatory – less than 10% relative risk reduction, which equates to a very small absolute reduction.

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Bolland MJ, Leung W, Tai V, et al. Calcium intake and risk of fracture: systematic review. BMJ. 2015; 350: h4580.