The study was conducted by researchers from Trinity College Dublin in Ireland and the University of Edinburgh (UoE) in Scotland. It has been published in the journal Scientific Reports.
Previous studies have found a strong link between vitamin D deficiency and increased susceptibility to viral and bacterial respiratory infection. Other studies have also found a strong correlation between COVID-19 and vitamin D deficiency.
But many of these studies have been ignored or belittled, with scientists attempting to argue that the increased susceptibility could be due to other factors such as older age, obesity or chronic illness. (Related: Since COVID-19 vaccines are said to be free for the "health of the nation," why aren't they giving away vitamin D and other vital supplements?)
To make sure detractors can't mistake the effects of vitamin D for other demographic, health and lifestyle factors, the researchers found a way to calculate vitamin D levels of the study's participants based on their genetics.
This method is known as Mendelian randomization. According to The BMJ, it "uses genetic variation to investigate the relations between modifiable risk factors and health outcomes in observational data."
This approach gave the researchers a way to properly investigate any causal link between vitamin D and COVID-19.
The study involved nearly half a million individuals in the United Kingdom. The researchers looked at the vitamin D levels of the participants as predicted by their genetics and by UVB.
UVB rays are very important to vitamin D production in the skin. UVB rays from the sun hit cholesterol in skin cells, which provides the energy for vitamin D synthesis to occur.
The Mendelian randomization analysis was inconclusive, and the researchers believe the number of COVID-19 cases in the study is too small to convincingly determine a causal effect between genetically predicted vitamin D levels and COVID-19.
But the researchers did find that ambient UVB radiation at the place of residence of a person before a COVID-19 infection helped determine a person's chances of getting hospitalized or even dying from the coronavirus.
This strongly suggests that sunlight exposure, and therefore vitamin D, protects people against severe COVID-19 cases and even death.
Evropi Theodoratou, senior study researcher and professor of cancer epidemiology and global health at UoE, believes the study should convince the mainstream medical community that they need to be more accepting of studies that show vitamin D's effects against COVID-19.
"Given the lack of highly effective therapies against COVID-19, we think it is important to remain open-minded to emerging results from rigorously conducted studies of vitamin D," said Theodoratou.
Lina Zgaga, senior researcher on the study and associate professor in epidemiology at Trinity College's School of Medicine, believes another study needs to be conducted. She believes this study needs to be a randomized controlled trial that studies the relationship between vitamin D supplementation and COVID-19 infections.
"Our study adds further evidence that vitamin D might protect against severe COVID-19 infection," said Zgaga. "Conducting ap properly designed [experiment] … is critical. Until then, given that vitamin D supplements are safe and cheap, it is definitely advisable to take supplements and protect against vitamin D deficiency, particularly with winter on the horizon."
Learn more about the positive effects of vitamin D in fighting against the coronavirus by reading the latest articles at VitaminD.news.