Boston University study finds Vitamin D reduces COVID-19 risk

BOSTON — A vaccine for COVID-19 may be months away, but a new study finds there is something already on the market that would appear to reduce the risk of coronavirus infection.

It’s Vitamin D.

“Vitamin D modulates your immune system,” said Michael F. Holick, MD, PhD, professor of medicine, physiology, and biophysics at Boston University School of Medicine. "It improves your ability to fight infectious diseases, including viral infections.

The study, which appears in PLOS ONE, compared COVID-19 infection rates against blood levels of 25-hydroxyvitamin D in more than 190,000 U.S. patients. Holick called the findings ‘remarkable.’

“If you’re Vitamin D deficient, you have a 54% higher risk of acquiring this infection compared to people who were Vitamin D sufficient,” he said. “This was for all ages, for all ethnicities and for all latitudes in the United States in all 50 states. So whether you’re in California, Florida, or Alaska this still remained the same.”

Exposure to the sun’s UVB rays triggers a reaction in skin cells which makes Vitamin D. How then, to explain, that the three states with the highest number of COVID-19 cases are also among the sunniest: California, Texas, and Florida?

“You only get Vitamin D from the sun from about 10 a.m. until about 3 p.m.,” Holick said. “And there’s been a lot of controversy about sun exposure so people put sunscreen on that basically prevents you from making Vitamin D.”

Holick said Vitamin D insufficiency is actually very common in Florida and California because of sunscreen use -- and the fact many avoid the midday sun.

“You might think well, if you have a healthy diet you’re getting all the nutrients and Vitamin D you need... not true,” Holick said. “Because only oily fish like wild-caught salmon, mushrooms exposed to sunlight, and cod liver oil are the only natural forms of Vitamin D in your diet.”

Milk and fortified orange juice can add additional small amounts of Vitamin D, but Holick said that still doesn’t add up to enough.

He said supplementation is a safe and effective way to maintain healthy levels of Vitamin D.

“Infants 400 to 1000 units a day, children 600 to 1000 units a day. And teenagers, in my opinion, should be treated like adults: 1500-2000 units a day,” Holick said. “If you’re obese you need two to three times more.”

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