Published on 1st January 2017


Vitamin D supplements could help prevent acute respiratory infections such as colds, ‘flu, bronchitis and pneumonia, according to a study published in the British Medical Journal (BMJ).1

Analysing data from around 11,000 participants in 25 clinical trials of vitamin D supplementation, the researchers reported that daily or weekly vitamin D supplementation prevented respiratory tract infections, especially in those with the lowest baseline vitamin D levels (below 25 nmol/L).

They concluded that their results added “to the body of evidence supporting the introduction of public health measures such as food fortification to improve vitamin D status, particularly in settings where profound vitamin D deficiency is common”.

Professor Adrian Martineau, who led the study at Queen Mary University of London, said: "This major collaborative research effort has yielded the first definitive evidence that vitamin D really does protect against respiratory infections.”

Vitamin D is known to be important for bone and muscle health, and last year Public Health England (PHE) announced that adults and children over the age of one should consider taking a daily supplement containing 10 micrograms of vitamin D, particularly during the autumn and winter months when there is minimal sunshine exposure.2

However, not everyone agrees that widespread vitamin D supplementation is a good thing, and other studies have reported more conflicting results. Speaking of the findings of Martineau and colleagues, an editorial published in the same issue of the BMJ advises caution, saying that further trials are necessary before the results change clinical practice. The authors said: “We consider that current evidence does not support the use of vitamin D supplementation to prevent disease, except for those at high risk of osteomalacia [softening of the bones, often caused by a vitamin D deficiency], currently defined as 25-hydroxyvitamin D levels [an indicator of vitamin D status] less than 25 nmol/L.”

The studies included in the analysis were randomised, double-blind, placebo-controlled trials (i.e. the “gold standard” of epidemiologic studies) of supplementation with vitamin D3 or vitamin D2. The trials were conducted in 14 countries on four continents and enrolled participants of both sexes from birth to 95 years of age.


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  1. Martineau AR et al (2017). Vitamin D supplementation to prevent acute respiratory tract infections: Systematic review and meta-analysis of individual participant data. BMJ, 356, i6583.
  3. Bolland MJ & Avenell A (2017). Do vitamin D supplements help prevent respiratory tract infections? [Editorial]. BMJ, 356.