Q: Does vitamin D help protect against COVID-19? A: Some scientists have hypothesized vitamin D might be helpful, but there is no direct evidence that vitamin D can prevent COVID-19 or lessen disease severity. Nevertheless, it should be part of a healthy lifestyle.
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Does Vitamin D Protect Against COVID-19?
By
Jessica McDonald
Posted on June 8, 2020
Q: Does vitamin D help protect against COVID-19?
A: Some scientists have hypothesized vitamin D might be helpful, but there is no direct evidence that vitamin D can prevent COVID-19 or lessen disease severity. Nevertheless, it should be part of a healthy lifestyle.
FULL QUESTION
Could vitamin D help decrease the chance of covid 19?
FULL ANSWER
As the coronavirus has spread around the globe, some scientists have proposed that vitamin D could help with COVID-19, the disease caused by the virus.
Former Centers for Disease Control and Prevention Director Dr. Tom Frieden, for example, published a March 23
column on Fox News’ website suggesting that vitamin D could reduce a person’s COVID-19 risk.
“There are many crackpot claims about miracle cures floating around,” he wrote, “but the science supports the possibility – although not the proof – that Vitamin D may strengthen the immune system, particularly of people whose Vitamin D levels are low.”
The idea stems in part from experiments that have found that the vitamin, which is synthesized in the skin after sun exposure and is found in select foods, is
used by the immune system. Some
research also suggests vitamin D supplements might protect against respiratory infections, especially if someone is deficient in the vitamin. And many of the people most affected by the coronavirus, such as the elderly and minority populations, tend to have lower vitamin D levels.
But experts caution against overinterpreting preliminary correlations or hypothetical mechanisms. As Pennsylvania State University
nutrition researcher A. Catharine Ross told us, associations are not the same as cause and effect, and the evidence either for or against vitamin D and COVID-19 is “extremely weak.”
A
rapid review from Oxford University’s Centre for Evidence-Based Medicine found “no clinical evidence” that vitamin D could prevent or treat COVID-19, and another
review on the topic published by nearly two dozen nutrition experts in
BMJ Nutrition, Prevention & Health recommended avoiding vitamin D deficiency, but warned against taking high doses of the vitamin.
“As a key micronutrient,” the authors wrote, “vitamin D should be given particular focus—not as a ‘magic bullet’ to beat COVID-19, as the scientific evidence base is severely lacking at this time—but rather as part of a healthy lifestyle strategy to ensure that populations are nutritionally in the best possible place.”
Thus, while it’s a good idea to get enough vitamin D — pandemic or not — it’s too early to say that a lack of vitamin D makes COVID-19 worse, or that supplementing with vitamin D provides any protection against the disease.
Vitamin D Basics
Although called a vitamin, vitamin D acts as a hormone in the body, and is best known for building strong bones, which is done in large part by promoting
absorption of calcium and phosphorus in the intestine.
“It’s actually a prohormone, and of all the nutrients that we have, it’s the only nutrient where the main source is not diet,” said
Susan Lanham-New, a vitamin D researcher at the University of Surrey in the U.K.
Instead, she told us, most of a person’s vitamin D is made in the skin upon exposure to sunlight, which is why darker-skinned people are
more likely to have lower levels of the vitamin, and why people who go outside less frequently, including those who are older or less healthy, are susceptible to deficiencies.
For vitamin D to be used by the body, it must be converted into an active form, typically by the liver and kidney, according to a National Institutes of Health
fact sheet. The nutrient is found naturally in only a few foods, such as eggs and oily fish, but is more widely available in the U.S. in food that has been fortified, including milk and cereals.
While there is a
debate about exactly how much vitamin D a person needs, and what constitutes a deficiency, Lanham-New said a commonly used metric for deficiency is a blood level below 25-30 nanomoles per liter. Too little vitamin D can
lead to rickets in children or osteomalacia in adults — conditions in which bones become soft and deformed.
More is not always better, however, since vitamin D is fat-soluble, and is stored in the body. “You can get what we call hypercalcemia if you take too much vitamin D,” Lanham-New said, referring to elevated levels of calcium in the blood that can be
especially dangerous for those with kidney diseases.
Vitamin D and Immunity
Beyond its role in bone health, vitamin D is also known to function in the immune system, which is a key reason why some think it’s plausible the nutrient might impact COVID-19.
Lanham-New, for example, said that vitamin D receptors are present on immune cells, and some immune cells make enzymes that help convert the nutrient into an active form.
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