Vitamin D Prevents Respiratory Infections, Says New Study

A large-scale meta-analysis using more than 10,000 participants concludes that vitamin D supplementation may help prevent a major cause of global death - acute respiratory tract infections.

Including anything from the common cold to pneumonia and bronchitis, they were the cause of an estimated 2.65 million deaths globally in 2013.

Respiratory tract infections have a wide array of risk factors, including overcrowding, a damp living environment, air pollution, and parental smoking.

A number of observational studies have also reported a nutritional risk factor -vitamin D deficiency. Some researchers have concluded that vitamin D has the ability to trigger an immune response to certain viruses and bacteria, medicalnewstoday.com reported.

The study was published this week in the BMJ.

The analysis, carried out by an international group of researchers, is the first to use individual participant data (IPD), rather than the aggregate methodology that was used in earlier meta-analyses. In this way, changes measured at different points in time within each participant of each trial can be accounted for, rather than taking a summary (aggregate) of the data. IPD is considered the “gold standard” of systematic review.

The team used data from 25 randomized controlled trials investigating vitamin D supplementation. In total, data from 11,321 participants were analyzed.

After adjusting for potentially confounding variables, such as sex, age, and study duration, they found that vitamin D supplementation produced a 12% reduction in the proportion of individuals experiencing at least one acute respiratory tract infection.

In simple terms, if 33 people took vitamin D supplements, one acute respiratory tract infection would be prevented. If these results are confirmed, vitamin D supplementation could potentially prevent millions of respiratory infections each year.

When the team drilled further into the data, they found that the positive effect was more pronounced in participants who took daily or weekly vitamin D without additional large doses. The effect was also stronger for individuals with more severe vitamin D deficiencies - only 1 in 4 people in this group would need to take vitamin D regularly to prevent one acute respiratory tract infection.

The authors said “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.”

The team also concluded that vitamin D was safe to consume as a supplement; side effects were rare.