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Vitamin D May Not Stop Respiratory Infections But It Can Ease Them, New Study Suggests


Tom Hale

Senior Journalist

clockJan 15 2021, 18:52 UTC
Vitamin D.

Vitamin D is naturally present in a few foods and produced by the body in response to skin being exposed to sunlight. Image credit: FotoHelin/

New research has weighed in on the much-hyped topic of Vitamin D and whether it can help to prevent respiratory infections. While the study found that Vitamin D supplements do not protect most people from developing colds, flu, and other acute respiratory infections, they might help to reduce the length and ease the severity of the illness.

Scientists at the QIMR Berghofer Medical Research Institute in Australia analyzed data on 16,000 people in Australia aged between 60 and 84. The participants were given either 60,000 international units of vitamin D or a placebo, every month for up to five years and were asked to complete an annual health report, as well as a winter diary, to keep track of how many illnesses they caught.


"Our clinical trial showed that people who took vitamin D supplements were infected with colds and flus at the same rate as those who were given placebos. Those who got the supplements did, however on average, report a small reduction in the number of days they experienced symptoms (on average about half a day)," Professor Rachel Neale, lead researcher and head of QIMR Berghofer's Cancer Aetiology and Prevention group, said in a statement.

"The findings suggest that vitamin D might give the immune system a little boost, but supplementing the general population with vitamin D is unlikely to protect people from getting sick in the first place and won't markedly improve the speed of recovery.”

The findings were reported this week in The Lancet Diabetes and Endocrinology.


However, the researchers were quick to point out a few caveats to their study. Primarily, vitamin D deficiency is not a widespread problem in Australia, where this study was carried out, but many countries report a very high prevalence of low vitamin D status. They argue that this has some potential to skew their results.

“It is possible that a greater protective effect would be seen in countries where a high proportion of the population is vitamin D deficient,” added Professor Neale.

Vitamin D is a fat-soluble vitamin that is naturally present in a few foods and produced by the body in response to skin being exposed to sunlight. It plays many vital roles in the body, not least some effects involving immune functions. Deficiency has been linked to an increased risk or severity of viral infections and disease. However, its ability to prevent common colds is not quite clear cut.


Recent months have seen a lot of debate about whether vitamin D can be used in the fight against COVD-19. Overall, the evidence supporting this idea is mixed, but some studies have suggested vitamin D may have some ability to manage severe cases of COVID-19.

This new study was carried out before the COVID-19 pandemic emerged, so it can’t make any reliable conclusions about its relationship with Vitamin D. After all, common respiratory infections are very different to COVID-19 and not easily comparable.

Professor Neale noted that anyone who was concerned about their vitamin D levels should speak to their doctor.

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