In a new study, researchers found that supplementary vitamin D can provide a certain degree of protection against respiratory infections.
The research was conducted by a team from Karolinska Institutet and elsewhere.
Whether vitamin D can reduce the risk of infection is still an open issue.
Four years ago, a synthesis of the current research was published that showed that vitamin D supplementation can provide a certain degree of protection against respiratory infections.
In the study, the team expanded the earlier material with an additional 18 studies and carried out new analyses.
Their results are based on 43 studies on the possible link between vitamin D and respiratory infections involving almost 49,000 participants.
The material the researchers have drawn on comprised published as well as registered but as yet unpublished studies, and is the most comprehensive such compilation to date.
The study adds further information about vitamin D as a protection against respiratory infections but does not cover the question of whether vitamin D can protect against COVID-19.
While the total protective effect against respiratory infections was 8%, the researchers found, for example, that a daily dose of vitamin D is much more effective than one given every week or month. There is no reason, either, to exceed the recommended dose.
Those who received 400-1000 IU/day had the best response, as the group that received such a dose demonstrated a reduction in infection risk of 42%.
The team wants to stress that there were no signals in the study that normal doses of vitamin D were dangerous or caused adverse reactions.
They say that the healthcare services should be more alert to groups that have a known risk of vitamin D deficiency, such as people with dark skin, overweight people and the elderly.
The study is published in The Lancet Diabetes & Endocrinology. One author of the study is Peter Bergman.
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