Seasonal declines in mean vitamin D levels were followed by seasonal increases in TB notifications.
Extended sun exposure was a major component of the pre-antibiotic era treatment of tuberculosis (TB) in sanitariums, based on Nobel Prize–winning work showing that cutaneous TB responds to light therapy. Now, a cross-sectional study in Cape Town, South Africa, once again points to a role for vitamin D in TB.
Investigators measured vitamin D levels in 370 adults with latent or active TB between April 2005 and January 2010; about half of the participants were HIV positive. Vitamin D deficiency was highly prevalent, with 63% of the study population having serum 25-hydroxyvitamin D levels <50 nmol/L. Patients with active TB had significantly lower mean vitamin D levels than those with latent TB, with the association appearing even stronger for HIV-positive than for HIV-negative individuals. Vitamin D levels varied substantially by season — and TB notifications followed suit. The reporting of new TB cases was lowest in the months that immediately followed seasonal summer peaks in vitamin D levels — and highest in the months that followed seasonal troughs.
Comment: The authors acknowledge that, given the study design, they cannot exclude the possibility that the observed association is due to active TB lowering vitamin D levels. However, the study results are supported by in vitro work showing that the antimicrobial activity of macrophages is dependent on vitamin D. Clinical trials on the potential of vitamin D to prevent and treat TB seem warranted.
ARYAN'S BLOG 