This systematic review and meta-analysis investigated the use of vitamin D supplementation as a way of preventing acute respiratory tract infections such as flu, bronchitis and pneumonia. The vaccine created to protect against influenza, by comparison, has a rate of protection of roughly one person for every 40 people who have received the vaccine, according to a 2014 study.
There's preliminary evidence that adequate amounts of vitamin D might help lower rates of respiratory infections. A number of clinical trials have been conducted to investigate the protective ability of vitamin D supplementation; but while some found a protective effect, others did not.
The use of Vitamin D supplements can help to protect against acute respiratory infections, according to a new study.
It's always been known that Vitamin D helps protect our bones, but evidence of the benefits of taking Vitamin D supplements to help guard immunity has been more controversial.
Technically, two different vitamins - D2, which mainly comes from supplements and food, and D3, which comes from the sun - the fat-soluble vitamin D works in our bodies to help build up bone strength.
Acute respiratory tract infections are responsible for 10 percent of ambulance and emergency room visits in the United States. For the new study, a meta-analysis published in The BMJ, researchers looked at individual data from almost 11,000 people who had participated in randomized controlled trials in more than a dozen countries.
"Vitamin D fortification of foods provides a steady, low-level intake of vitamin D that has virtually eliminated profound vitamin D deficiency in several countries", he explained.
Vitamin D is thought to protect against illness by boosting levels of natural, antibiotic-like peptides in the lungs. And pregnant and nursing women, as well as women with osteopenia or osteoporosis, often need more vitamin D to maintain bone health.
But people with higher baseline vitamin D levels also benefited, although the effect was more modest, equalling a 10 per cent risk reduction. The only health problem that can be prevented by vitamin D supplements is osteomalacia.
"We consider that current evidence does not support the use of vitamin D supplementation to prevent disease, except for those at high risk of osteomalacia, now defined as 25-hydroxyvitamin D levels less than 25 nmol/L", they wrote. Daily or weekly supplementation with vitamin D sure did have a positive effect on those who were deficient in the vitamin. Taking vitamin D supplements would even be more effective than a flu vaccination, the research suggested, sparing infection for one person in every 33, compared with one in 40 who receive a flu vaccination.
And in 2014, the U.S. Preventive Services Task Force said there's not enough evidence of benefit for all people to be routinely tested for vitamin D deficiency.