A recent study by Israeli scientists found “striking” differences in the chances of contracting severe COVID-19 illness between individuals with sufficient levels of vitamin D prior to catching the virus and those who did not.
Half the vitamin-deficient people developed severe, life-threatening illness compared to fewer than 10 percent of those who had normal levels. The study is the first to examine existing vitamin levels in people before they contracted COVID. “We found it remarkable, and striking,” said the lead author, “to see the difference in the chances of becoming a severe patient when you are lacking in vitamin D compared to when you’re not.”
The data come from 253 people who were admitted to a hospital between April 7, 2020 and February 4, 2021—a period of time before the highly-infectious Omicron variant appeared. The results, however, are “equally relevant” for Omicron as for previous strains, say the study authors.
Vitamin D is largely synthesized naturally in human skin and requires direct exposure to sunlight (specifically, UV-B). Artificial light, no matter how bright, doesn’t cut it. Given how the pandemic has kept many people primarily indoors for over two years, it is easy to see how a considerable number of individuals might have fallen below the threshold for adequate vitamin levels—which conventionally is at least 20 nanograms per milliliter of blood.
New data, however, indicate that even this is too low. A minimum level of 50 mg/mL is now advised. Levels below his are said to cause weak innate immune responses to common that which cause post-operative infections.
Diet plays a much lesser role in the vitamin’s intake and maintenance. It is soluble in fat rather than water, and found in foods such as fresh fatty fish, mushrooms, egg yolks, full-fat yoghurt, beef liver, and duck. According to Prof. Robin Wright of Victoria, Australia, the quantity of Vitamin D3 is food is quite small.
For most people with inadequate sun exposure “the only practical way of ensuring good levels … is vitamin D3 supplements,” says Prof. Wright.
Throughout the life span the vitamin regulates the metabolism of calcium, which is crucial for the development and maintenance of healthy bones. It prevents rickets in children and osteoporosis in adults. The latter results in brittle bones and, correspondingly, otherwise avoidable fractures.
Muscle and bone weakness also render individuals prone to falls. Its active metabolite acts as a hormone that targets the kidney and other organs, giving it a role in heart disease, diabetes, cancer, and immune cells (this last is a complex topic beyond the scope of this column).
Research published in The Lancet and compiled before the emergence of COVID varieties found that, compared to dummy drugs, adequate vitamin D also reduced the risk of contracting other respiratory infections.
The Israeli researchers cautioned that vitamin D was only “one piece of the complex puzzle” underlying cases of severe COVID-19. It alone doesn’t constitute proof of cause. Yet it does seem to serve as a useful marker to flag individuals who may go on to develop serious illness.