Practice Uncertainties

Should adults take vitamin D supplements to prevent disease?

BMJ 2016; 355 doi: https://doi.org/10.1136/bmj.i6201 (Published 23 November 2016) Cite this as: BMJ 2016;355:i6201
  1. Mark J Bolland, associate professor1,
  2. Alison Avenell, professor2,
  3. Andrew Grey, associate professor1
  1. 1Department of Medicine, University of Auckland, Auckland 1142, New Zealand
  2. 2Health Services Research Unit, University of Aberdeen, Aberdeen AB25 2ZD, Scotland
  1. Correspondence to: M Bolland m.bolland{at}auckland.ac.nz

What you need to know

  • Meta-analyses of randomised controlled trials (RCTs) show that vitamin D supplementation alone does not improve musculoskeletal outcomes

  • Meta-analyses of randomised controlled trials of vitamin D on non-musculoskeletal outcomes suggest ongoing uncertainty:

    • There is no high quality evidence to suggest that it is beneficial for these outcomes

    • There is insufficient evidence to conclude firmly against small benefits, but RCT results exclude beneficial effects of a size suggested by observational studies

    • The clinical trials currently under way are unlikely to answer these uncertainties

The US Preventive Services Task Force recommends against vitamin D and calcium supplementation for fracture prevention in otherwise healthy postmenopausal women.1 However, despite high quality systematic reviews reporting ineffectiveness, many guideline groups continue to recommend vitamin D supplementation (with or without calcium) for fall or fracture prevention. Recently Public Health England recommended that everyone needs vitamin D equivalent to an average daily intake of 10 μg (400 IU) to protect bone and muscle health,2 and more than 30-50% of older people in some Western countries take vitamin D supplements.3 4 The role of vitamin D supplementation in individuals not at high risk of osteomalacia (box 1) has been extensively investigated in recent years, but some uncertainties remain.

BOX 1: Vitamin D facts

  • Vitamin D is a prohormone synthesised in the skin in response to ultraviolet-B radiation in sunlight

  • Dietary sources are limited and include oily fish, egg yolk, red meat, liver, and fortified breakfast cereals, fat spreads, and milk in some countries

  • Vitamin D is needed to ensure adequate intestinal absorption of calcium to maintain normal serum calcium levels

  • The best current test for vitamin D status is serum 25-hydroxyvitamin D

  • 25-hydroxyvitamin D level <25 nmol/L is classified as vitamin D deficiency. Classifications of vitamin D sufficiency vary, ranging from ≥50 nmol/L to ≥80 nmol/L

  • Those at high risk of vitamin D deficiency include people who …

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