Vitamin D supplements don't lower risk of acute respiratory tract infection: Lancet

Australia: Monthly doses of vitamin D supplementation (60000 IU) does not reduce the risk of acute respiratory tract infection but slightly reduced the duration of symptoms, according to a recent study. The findings of the study, published in the journal Lancet: Diabetes and Endocrinology, suggest that routine supplementation of vitamin D in vitamin D replete people, is unlikely to have clinically relevant effect on acute respiratory tract infection.

Observational studies have shown vitamin D deficiency to be linked to acute respiratory tract infection but results obtained from randomized controlled trials have been heterogeneous. Hai Pham, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia, and colleagues aimed to determine if supplementation with monthly doses of vitamin D reduces the duration, risk, and severity of respiratory tract infections. 

For the purpose, the researchers used data from the D-Health Trial -- a double-blind, placebo-controlled trial of monthly vitamin D supplementation. The pre-specified of the trial was acute respiratory infection.

Between Jan 13, 2014, and May 26, 2015, 421 207 invitations were sent, 40 824 people were interested in participating, and 21 315 participants were recruited and randomised. Of the 16 000 participants selected for potential analysis of survey data, 15 373 were included in the analysis; 295 in the vitamin D group and 332 in the placebo group who were missing data for all five annual surveys were excluded from the analysis. Of the 3800 selected for potential analysis of diary data, 3070 were invited to complete the diaries because 730 had already withdrawn. 2598 people were included in the analysis; 218 people in the vitamin D group and 254 in the placebo group were missing data and were therefore excluded from the analysis. 

"Monthly bolus doses of 60 000 IU of vitamin D did not reduce the overall risk of acute respiratory tract infection, but could slightly reduce the duration of symptoms in the general population," wrote the authors.

"These findings suggest that routine vitamin D supplementation of a population that is largely vitamin D replete is unlikely to have a clinically relevant effect on acute respiratory tract infection," they concluded. 

"The effect of vitamin D supplementation on acute respiratory tract infection in older Australian adults: an analysis of data from the D-Health Trial," is published in the journal Lancet: Diabetes and Endocrinology.

DOI: https://www.thelancet.com/journals/landia/article/PIIS2213-8587(20)30380-6/fulltext