Vitamin D supplementation has been linked to numerous benefits, from preventing rickets to improving immune function and cardiovascular health. While the function of vitamin D in bone growth and maintenance is clear, the debate on its role in lowering the odds of developing respiratory tract infection has been going on. Different studies have yielded mixed results. One more study has further escalated the discussion.
A five-year clinical trial, led by Brisbane's QIMR Berghofer Medical Research Institute, concluded that vitamin D supplements will not protect from catching colds, flus and other respiratory infections. The trial, involving 16,000 Australians aged between 60 and 84, is claimed to be the largest of its kind to study the relationship between vitamin supplements and respiratory infections.
Half of the participants were given a vitamin D capsule once a month for five years, while the other half were given a placebo or sugar tablet for the same period. The researchers found that while taking vitamin D did not stop people from getting respiratory tract infections, it reduced the length and severity of infection in some cases.
Based on these findings, lead researcher Professor Rachel Neale said that taking vitamin D is unlikely to stop people from getting a head cold or the flu, if they are not vitamin D deficient.
"It may reduce the length of it a little bit, but not enough to really warrant taking vitamin D if you're not already vitamin D deficient," ABC News quoted Neale as saying.
Vitamin D: More is not better
The findings of this study suggest that more is not better, noted Neale cautioning against unnecessary supplementation. This means if you're not vitamin D deficient and if you're getting a bit of sun exposure particularly during summer, you don't need to run out and get a supplement, she elaborated.
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However, Neale pointed out that being aware of avoiding vitamin D deficiency is important.
The Institute's five-year trial concluded just before the coronavirus pandemic strikes the world. Though they didn't measure coronavirus, Professor Neale said the study results may be still relevant in the current situation.
According to Neale, their finding of a reduced length and severity of infection, albeit a small reduction, indicates that perhaps vitamin D does influence the immune system in people.
"And that means that in people who are vitamin D deficient, if we were to treat their deficiency, that might have some benefit for their immune system and arguably some benefit for the coronavirus," she was quoted in the ABC News report.
The study results were published in The Lancet Diabetes & Endocrinology.
Vitamin D and coronavirus infection
There are also different opinions regarding the efficiency of vitamin D in fight against the novel coronavirus. A study by researchers from the Tabriz Health Services Management Research Center, Tabriz University of Medical Sciences, and the Shahid Beheshti University of Medical Sciences suggested that vitamin D supplement can help reduce Covid-19 mortality rate, its severity and serum levels of inflammatory markers.
The research, published on the medRxiv* server, cited three studies that found the mortality rate is lower among patients who received vitamin D supplementation than the control group. The intervention group had a lower rate of admission in the intensive care unit (ICU) as well as a substantial reduction in serum levels of fibrinogen, which rises in any condition that causes inflammation or tissue damage.
Low Vitamin D level has been associated with reduced immune function, which may increase the risk of severe COVID-19 complications. While some researchers postulate vitamin D supplementation may reduce complications in people with COVID-19, multiple clinical trials are still investigating the effects of vitamin D supplementation.
Take away: It's advisable to have your healthcare provider test your vitamin D levels before you consider taking supplements.