Vitamin D can help build resistance to Covid-19, two crucial Irish scientific studies have found.
One of the studies, published in the Irish Medical Journal, calls for the immediate vitamin D supplementation of hospital inpatients, nursing home residents and older people.
It suggests that vitamin D supplementation in the wider adult population, particularly in frontline healthcare workers, may further limit infection and flatten the Covid-19 curve.
Researchers from Technological University Dublin and Trinity College Dublin, recommend that Irish adults take 20 to 50 micrograms of vitamin D every day.
Vitamin D deficiency is prevalent in Ireland, especially in older people, and may significantly increase the risk and severity of viral respiratory infections.
The authors believe vitamin D supplementation was important in the absence of a vaccine and evidence of effective drug treatment for Covid-19.
Another report from the Irish Longitudinal Study on Ageing (TILDA) at TCD emphasises the importance of increasing vitamin D by older people who are staying at home or cocooning.
Their report finds that vitamin D plays a critical role in preventing respiratory infections, reducing antibiotic use and boosting the immune system response to infections.
With one in eight Irish adults under 50 deficient in vitamin D, the report highlights the importance of increasing intake.
Vitamin D is produced in the skin by exposing the body to just 10-15 minutes per day of sun. In Ireland, vitamin D can only be made between late March and early September.
People who get little sun exposure or eat inadequate amounts of fortified foods are most at risk, especially those currently house-bound or confined to their homes.
TILDA researchers recommend that adults over 50 should take supplements, not just in winter but all year round if they don't get enough sun.
Those who are currently cocooning should also take supplements.
TILDA principal investigator, Prof Rose Anne Kenny, said they have “very strong evidence” to support a role for vitamin D in the prevention of chest infections, particularly in older adults who have low levels.
“In one study vitamin D reduced the risk of chest infections to half in people who took the supplement,” she said.
"Though we do not know specifically of the role of vitamin D in Covid-19 infections, given its wider implications for improving immune responses and clear evidence for bone and muscle health, those cocooning and other at-risk cohorts should ensure they have an adequate intake of vitamin D.”
Prof Kenny said cocooning is also reduced physical activity.
"Muscle deconditioning occurs rapidly in these circumstances and vitamin D will help to maintain muscle strength in the current crisis."
Prof Kenny said there is also good evidence that vitamin D helps the mood.
“If you have low vitamin D you are more likely to have a low mood.”
Co-author of the report, Eamon Laird, said vitamin D was not inevitable because eating oily fish, eggs, vitamin D-fortified cereals or dairy products with a daily 400 IU (10ug) vitamin D supplement could help avoid it.
“However, Ireland needs a formal vitamin D food policy or recommendation, which we are still lacking,” he said.
He pointed out that Finland had such a policy and had virtually eliminated deficiency in their population.