Editorials

Low vitamin D levels as a risk factor for cancer

BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j4952 (Published 31 October 2017) Cite this as: BMJ 2017;359:j4952
  1. Despoina Manousaki, paediatric endocrinologist1,
  2. J Brent Richards, endocrinologist and associate professor1 2 3
  1. 1Centre for Clinical Epidemiology, Department of Epidemiology, Lady Davis Institute for Medical Research, Jewish General Hospital, McGill University, Montreal, Quebec, Canada
  2. 2Departments of Medicine, Human Genetics, Epidemiology and Biostatistics, Jewish General Hospital, McGill University Montreal, Quebec, Canada
  3. 3Department of Twin Research and Genetic Epidemiology, King’s College London, London, UK
  1. Correspondence to: J B Richards brent.richards{at}mcgill.ca

New evidence challenges the benefits of vitamin D supplementation for cancer prevention

Arguably, to date the most clinically effective way to reduce the burden of cancer has been through primary prevention.1 One promising such strategy has been to target vitamin D insufficiency as epidemiological and animal studies have found that low levels of vitamin D are associated with an increased risk of cancer.23 Furthermore, vitamin D insufficiency affects 40% of the general population,4 is easily diagnosed by a simple blood test, and can be treated safely and inexpensively. This may partially explain the 60-fold increase in the use of vitamin D supplements in the US general population between 2000 and 2014, where 18% currently take ≥1000 IU of vitamin D daily.5

Limiting bias

Yet the most prudent way to test the efficacy of vitamin D would be through large scale randomised controlled trials because observational studies may be biased by residual confounding (vitamin D levels are confounded by known drivers of cancer risk, such as smoking, obesity, and the healthy user effect6). Yet such trials are …

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