Head To Head

Should healthy people take a vitamin D supplement in winter months?

BMJ 2016; 355 doi: https://doi.org/10.1136/bmj.i6183 (Published 23 November 2016) Cite this as: BMJ 2016;355:i6183
  1. Tim D Spector, professor of genetic epidemiology1,
  2. Louis Levy, head of nutrition science2
  1. 1King’s College London, UK
  2. 2Public Health England, London, UK
  1. Correspondence to: T D Spector, tim.spector{at}kcl.ac.uk, L Levy dominique.lemon{at}phe.gov.uk

Yes—Louis Levy

Getting enough vitamin D to protect musculoskeletal health requires eating the right types of food and getting short bursts of daily sunshine in summer months. However, for many people this can be harder to achieve than it sounds, and some people will need to take supplements in autumn and winter.

The Scientific Advisory Committee on Nutrition (SACN) reviewed previous recommendations1 in the light of public health advice to stay out of the sun and wear sunscreen and accumulation of new evidence on vitamin D. It has recommended a reference nutrient intake—the amount that is sufficient to meet the needs of 97.5% of the population—for vitamin D of 10 μg a day to protect musculoskeletal health in people aged 4 years or older.2

Population protection

SACN based its recommendation on a review of the evidence on musculoskeletal health outcomes, concluding that there was insufficient evidence to make dietary recommendations on non-musculoskeletal outcomes and the risk of poor musculoskeletal health is increased at serum 25-hydroxyvitamin D concentrations below 25 nmol/L.2 This concentration is not diagnostic of disease but indicates the level below which risk of poor musculoskeletal health is increased; it represents a population protective level. On the basis of modelling work, SACN estimated that 10 μg/day is the amount of vitamin D needed for 97.5% of the population to maintain blood concentrations at or above 25 nmol/L when exposure to sunshine is minimal.2

SACN’s evaluation adhered to its framework for the evaluation of evidence,3 which is based on an evidence hierarchy used to judge the strength of each study according to design. Most weight is generally placed on randomised controlled trials since only this study type can demonstrate a causal relation between an intervention and …

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