Vitamin D supplementation not associated with reduced cancer risk
Vitamin D supplementation should not be recommended as the primary strategy for cancer prevention.
Population-wide screening for vitamin D deficiency and subsequent widespread vitamin D supplementation should not currently be recommended as a strategy for primary cancer prevention, according to research published in the BMJ.
Vasiliki I Dimitrakopoulou, from the Department of Hygiene and Epidemiology, School of Medicine at the University of Ioannina in Greece, and colleagues retrieved summary data for the association between single nucleotide polymorphisms associated with vitamin D and cancer from 3 large genetic epidemiology networks. These networks were the Genetic Associations and Mechanisms in Oncology (GAME-ON), the Genetic and Epidemiology of Colorectal Cancer Consortium (GECCO), and the Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome (PRACTICAL) consortiums as well as the MR-Base platform.
Participants included 70,563 cancer patients: 22,898 prostate cancer, 15,748 breast cancer, 12,537 lung cancer, 11,488 colorectal cancer, 4,369 ovarian cancer, 1,896 pancreatic cancer, and 1,627 neuroblastoma, compared with 84,418 controls. Four single nucleotide polymorphisms (rs2282679, rs10741657, rs12785878 and rs6013897) associated with vitamin D were used to define a multi-polymorphism score for circulating 25-hydroxyvitamin D (25(OH)D) concentrations.
The primary outcomes were the risk of incident colorectal, breast, prostate, ovarian, lung, and pancreatic cancer and neuroblastoma, which was evaluated with an inverse variance weighted average of the associations with specific polymorphisms and a likelihood based approach. Secondary outcomes based on cancer subtypes by sex, anatomic location, stage, and histology were also examined.
The researchers found little evidence that the multi-polymorphism score of 25(OH)D was associated with risk of any of the 7 cancers or their subtypes. Specifically, the odds ratios per 25 nmol/L increase in genetically determined 25(OH)D concentrations were 0.92 for colorectal cancer, 1.05 for breast cancer, 0.89 for prostate cancer, and 1.03 for lung cancer. Based on Mendelian randomization analyses with either the inverse variance weighted method or the likelihood based method, there was little evidence that the multi-polymorphism scores for continuous 25(OH)D concentration were associated with risk of colorectal, breast, prostate, ovarian, lung, or pancreatic cancer and neuroblastoma.
“In summary, using a comprehensive Mendelian randomization study, we found little evidence for linear causal associations between genetic determinants of circulating vitamin D concentration and risk of colorectal, breast, prostate, ovarian, lung, and pancreatic cancer and neuroblastoma, but we cannot rule out the existence of causal clinically relevant effects of low magnitude,” the authors concluded.
Dimitrakopoulou VI, Tsilidis KK, Haycock PC, et al. Circulating vitamin D concentration and risk of seven cancers: Mendelian randomisation study. BMJ. 2017 Oct 31;359:j4761. doi: 10.1136/bmj.j4761