Can Vitamin D Prevent Respiratory Tract Infections?

A new study finds that vitamin D supplementation is associated with lower rates of acute respiratory tract infections, especially in people who are vitamin D deficient. 

The study appears in the February 15 online issue of the BMJ.

This was a systematic review and meta-analysis of individual participant data from randomized, double-blinded, placebo controlled trials of vitamin D3 or vitamin D2 supplementation of any duration. Studies included in this analysis were collected from the following databases:  ClinicalTrials.gov, the International Standard Randomised Controlled Trials Number registry, Medline, Embase, the Cochrane Central Register of Controlled Trials, and Web of Science.

Led by Adrian Martineau, Ph.D., of Queen Mary University of London in the United Kingdom, the objective of the study was to evaluate the effect of vitamin D supplementation on developing acute respiratory tract infections and identify factors that may affect this relationship.

A total of 25 studies (out of 532 unique studies assessed for eligibility) were included in the final analysis, representing 11,321 participants ages 0 to 95. The time period for analysis was from inception through December 31, 2015.

The research team found that vitamin D supplementation reduced the risk of acute respiratory tract infections for all participants (adjusted odds ratio 0.88, 95% confidence interval 0.81 to 0.96; p <0.001). In people those taking daily or weekly vitamin D supplementation without extra bolus doses, protective effects were also observed (adjusted odds ratio 0.81, CI: 0.72 to 0.91). However, no protective benefit was seen in those receiving one or more bolus doses of vitamin D supplementation.

Another interesting finding is that among those who had daily or weekly vitamin D supplementation, the strongest protection against acute respiratory infections was observed in those with baseline 25-hydroxyvitamin D levels of <25 nmol/L (adjusted odds ratio 0.30, CI; 0.17 to 0.53) compared to those with baseline 25-hydroxyvitamin D levels ≥25 nmol/L (adjusted odds ratio 0.75, CI:0.60 to 0.95; P=0.006).

Baseline vitamin D status and dosing frequency modified the relationship between vitamin D supplementation and acute respiratory tract infections; however, age was not a factor.

Acute respiratory tract infections are responsible for approximately 10 percent of ambulatory and emergency room visits in the United States. In 2013, an estimated 2.6 billion deaths internationally were attributed to acute respiratory tract infections. To date, observational studies have shown an association between low serum levels of 25-hydroxyvitamin D and risk of developing acute respiratory tract infections. Given that 25-hydroxyvitamin D supports induction of antimicrobial peptides in response to bacterial and viral stimuli, it is hypothesized that vitamin D supplementation may be one way to protect against respiratory pathogens.

“Our study reports a major new indication for vitamin D supplementation:  The prevention of acute respiratory tract infection,” wrote Martineau and colleagues. “Our results add 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.”

Disclosures:

This research was supported by a grant from the National Institute for Health Research in the United Kingdom.

References:

Adrian R Martineau, David A Jolliffe, Richard L Hooper, et al. “Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data,” BMJ. Published online February 15, 2017.  DOI: 10.1136/bmj.i6583