Vitamin D may be an important factor in determining the severity of COVID-19 infections, new research from the Irish Longitudinal Study on Ageing (TILDA) at Trinity College Dublin has found.

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. Earlier this month, TILDA published a report which suggested that the vitamin plays an essential role in preventing respiratory infections, reducing antibiotic use, and boosting the immune system's response to infections.

According to these latest TILDA findings, there are major discrepancies in mortality rates related to vitamin D levels at different latitudes worldwide. Countries in the southern hemisphere, such as Australia, are recording relatively low COVID-related mortality, which the TILDA researchers state can no longer feasibly be related to the later appearance and spread of the virus.

They have pointed to the high prevalence of vitamin D deficiency in northern hemisphere countries, and the possible role of the vitamin in suppressing severe inflammatory responses seen in patients seriously ill with COVID-19.

The researchers explained that vitamin D deficiency correlates with poor sunlight exposure, increasing age, high blood pressure, diabetes, obesity and ethnicity. These are all features associated with an increased risk of severe COVID-19.

Currently, all countries that lie below a latitude of 35 degrees north have relatively low mortality from COVID-19. However, people in countries that lie 35 degrees north and above receive insufficient sunlight for adequate vitamin D levels in winter and spring. These include Italy and Spain, which have low population levels of vitamin D.

The researchers pointed out that mortality rates from COVID-19 are higher at these latitudes, with the exception of Nordic countries, where vitamin D supplementation is widespread and deficiency is much less common.

According to Prof Rose Anne Kenny principal investigator of TILDA, vitamin D benefits bone health, muscle health and the immune system, "in addition to a potentially critical role in suppression of the severe pro-inflammatory response which characterises severe COVID-19 complications".

As a result of their findings, the researchers are recommending that all nursing home residents in Ireland take Vitamin D.

"Public Health England, the Scottish and Welsh governments have issued recommendations for supplements for all adults from March to October, and supplementation all year round for adults living in care homes or nursing homes, who are required to wear clothes that cover most of the skin when outdoors, or who have dark skin.

"Similar public health recommendations are called for in Ireland. This advice is of importance given high mortality rates for COVID infection in our nursing home sector," she commented.

Meanwhile, Dr Eamon Laird of TILDA reminded people that vitamin D is present in foods such as oily fish (salmon, tuna, sardines), cheese, egg yolks and beef liver.

"However, supplementation is the best means of ensuring sufficient vitamin D blood levels. As the effects of coronavirus continue, many of us are limited in the time we can spend outdoors, so extra care is required to keep vitamin D levels healthy," he said.

The TILDA findings are published as an editorial in the current edition of the Journal of Alimentary Pharmacology and Therapeutics.