High doses of vitamin D supplementation cannot prevent, treat COVID-19: Study

There is currently insufficient scientific evidence to show that vitamin D can be beneficial in preventing or treating COVID-19, scientists say, warning against health risk due to high doses of supplementation. Following unverified reports that high doses of vitamin D could reduce the risk of contracting COVID-19, scientists, including those from the University of Manchester in the UK, assessed current scientific evidence base on the vitamin's use in treating infections.

"Until there is more robust scientific evidence for vitamin D, we strongly caution against the use of high vitamin D supplementation," the scientists wrote in a report, published in the journal BMJ Nutrition, Prevention and Health. The report noted that vitamin D is a hormone, produced in the skin during exposure to sunlight, and helps regulate the amount of calcium and phosphate in the body. These minerals, according to the researchers, are needed to keep bones, teeth and muscles healthy.

"An adequate level of vitamin D in the body is crucial to our overall health, too little can lead to rickets or the development of osteoporosis but too much can lead to an increase in calcium levels in the blood which could be particularly harmful," said Sue Lanham-New, lead author of the study from the University of Surrey in the UK. However, the researchers found no evidence of a link between high dose supplementation of vitamin D in helping to prevent or successfully treat COVID-19.

They cautioned against over-supplementation of the vitamin, without medical supervision, due to health risks. Assertions about the benefit of the vitamin in treating the virus are not currently supported by adequate human studies, and are based on findings from studies that did not specifically examine this area, they said. When the scientists assessed previous research on the link between vitamin D levels and respiratory tract ailments, they found that lower vitamin D status is associated with acute infections.

However, the researchers said, the findings from the majority of these studies were based on data gathered from population groups in developing countries, which cannot be extrapolated to all humans. According to the scientists, there is currently no firm link between vitamin D intake and resistance to respiratory tract infections. "Most of our vitamin D comes from exposure to sunlight, however for many people, particularly those who are self-isolating with limited access to sunlight during the current pandemic, getting enough vitamin D may be a real challenge," study co-author Carolyn Greig from Birmingham University in the UK.

In this context, while supplementing with vitamin D is recommended, it should be done under medical guidance, the scientists said. "Although there is some evidence that low vitamin D is associated with acute respiratory tract infections, there is currently insufficient evidence for vitamin D as a treatment for COVID-19 and over-supplementing must be avoided as it could be harmful," Greig added. The researchers said levels of the vitamin in the body can also be supplemented by a nutritionally balanced diet including foods that provide the vitamin, such as oily fish, red meat, and egg yolk. Fortified foods such as breakfast cereals, and safe sunlight exposure can also boost vitamin D status, they added.