Vitamin D and Health

6.286 Support for an immunomodulatory role has also been suggested by ecological studies showing
associations between seasonal variations in serum 25(OH)D concentration and incidence of various
infectious diseases including respiratory infection (Grant, 2008) and influenza (Cannell et al., 2006).
6.287 Possible mechanisms for the role of vitamin D in host resistance to pathogens is considered further in
a review by Lang et al. (2013). The review concludes that current epidemiological data suggest that
vitamin D deficiency increases susceptibility to various pathogens; however the underlying
mechanisms still require clarification and further investigation, including the role of inherited
polymorphisms in DBP, CYP27B1 and VDR genes.
6.288 IOM Report: The IOM considered the effect of vitamin D on tuberculosis (TB), influenza and upper
respiratory infections. It noted that results from RCTs and observational studies were inconsistent and
that prospective studies were limited by potential confounding. It concluded that overall the evidence
was not consistently supportive of a causal role for vitamin D in reducing the risk of developing
infectious disease.
Evidence considered since IOM report (Tables 50-52, Annex 2)
6.289 There is some evidence to suggest that vitamin D supplementation can influence the risk of
developing infectious disease; however, most of the evidence on vitamin D and infection relates to
use of vitamin D as a therapeutic agent in patients with pre-existing disease and considers whether
vitamin D supplementation reduces severity or progression of the disease.
6.290 Another difficulty that potentially complicates interpretation of the data on vitamin D and infection is
the reported decrease in serum 25(OH)D concentration during the acute phase response to
inflammation that occurs with infection (Silva & Furlanetto, 2015) (see paragraph 4.10).
Tuberculosis
6.291 TB is an infection caused by the bacterium Mycobacterium tuberculosis which typically affects the
lungs and is transmitted by inhalation of airborne particles. A person exposed to TB will not
necessarily develop the disease. Instead, the infection can remain inactive for many years; this is
known as latent TB infection (LTBI). If the host immune system becomes weakened the infection can
develop into active TB and spread to the lungs or other parts of the body, with symptoms developing
within a few weeks or months. The tuberculin skin test (TST) conversion is the standard method used
to determine whether a person is infected with M tuberculosis.
RCTs
6.292 Most RCTs have tested whether vitamin D therapy improves TB outcomes and might be used as an
adjunctive treatment. Only 1 feasibility trial on vitamin D supplementation for the prevention of
active TB in those with a latent infection could be identified. Ganmaa et al. (2012) assessed effects of
daily vitamin D supplementation (20 µg/800 IU) on resistance to TST conversion among healthy school
children in Mongolia (n=120; age, 12-15y). At baseline, mean serum 25(OH)D concentration was
18 nmol/L; 16 children in the vitamin D group and 18 in the placebo group were TST positive (p=0.7).
After 6 months of intervention, mean serum 25(OH)D concentration increased in the vitamin D
supplementation group (50 nmol/L) and decreased in the placebo group (10 nmol/L). TSTs converted
to positive in 5 (11%) children receiving vitamin D compared with 11 (27%) receiving placebo but this
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