A new Irish report has highlighted the key role vitamin D plays in preventing respiratory infections, which could have important implications for the fight against COVID-19 (coronavirus).

The report, Vitamin D Deficiency in Ireland - Implications for COVID 19, was released by researchers from the Irish Longitudinal Study on Ageing (TILDA) at Trinity College Dublin.

TILDA is an ongoing study of people over the age of 50 in Ireland.

According to the report, vitamin D plays an essential role in preventing respiratory infections, reducing antibiotic use, and boosting the immune system's response to infections.

However, an estimated 27% of Irish adults who are over the age of 70 and are currently cocooning as part of the COVID-19 response, are deficient in this key vitamin.

Vitamin D is known as the sunshine vitamin because it is produced in the skin by exposing the body to just 10-15 minutes per day of sunshine. In Ireland, vitamin D can only be produced in the skin between late March and late September. It cannot be produced in winter.

Even in summer, getting a sufficient amount of Vitamin D can pose a challenge, due to things like cloud cover, rainy weather and a lack of sunshine.

However, people can ensure they are not deficient by consuming an adequate amount of vitamin D-rich foods and by supplementation. Vitamin D is readily found in foods like eggs, liver and oily fish, such as salmon and mackerel, as well as fortified foods such as cereals and dairy products.

The TILDA report revealed that an estimated 27% of adults over the age of 70, who are currently cocooning, are deficient in the vitamin, while 47% of all adults over the age of 85 are deficient in winter.

A further one in eight adults over the age of 50 are deficient all year round, yet just 15% of women and 4% of men take a vitamin D supplement.

People most at risk of vitamin D deficiency are those who get little sun exposure and/or eat inadequate amounts of fortified foods, particularly those who are currently housebound or confined to their homes. Other high-risk groups include people with asthma or other chronic lung diseases, and obese or physically inactive people.

The TILDA researchers recommend that all adults over the age of 50 should take vitamin D supplements all year round if they do not get enough sun. Those who are cocooning should also take supplements.

"We have 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 supplements.

"Though we do not know specifically the role of Vitamin D in COVID 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," insisted TILDA principal investigator, Prof Rose Anne Kenny.

She also noted that while cocooning is a necessity at this time, it will reduce physical activity.

"Muscle deconditioning occurs rapidly in these circumstances and vitamin D will help to maintain muscle health and strength in the current crisis," she said.

Meanwhile, according to the report's co-author, Dr Eamon Laird, a research fellow in medical gerontology, these findings clearly show that Vitamin D deficiency is common, "which could have a significant negative impact on people's immune response to infection".

"There is an even larger risk now of deficiency with those cocooning or confined indoors. However, vitamin D deficiency is not inevitable. Eating foods such as oily fish, eggs, vitamin D-fortified cereals or dairy products, and a daily 400 IU (10ug) vitamin D supplement, can help avoid deficiency.

"However, Ireland needs a formal vitamin D food policy/recommendation, which we are still lacking. For instance, Finland has such a policy and has virtually eliminated deficiency in its population," he added.

Vitamin D is available without prescription.

The report can be viewed here.