UNC Health Care

Can Vitamin D Help Prevent COVID-19?

Since the beginning of the coronavirus disease 2019 (COVID-19) pandemic, people have turned to vitamins and other supplements to boost their immune systems in hopes of fighting off COVID-19. Vitamin D, in particular, has received attention as a potential safeguard against infection.

In recent studies that examined the effect of vitamin D on COVID-19, one found that people who had a vitamin D deficiency were more likely to test positive for the virus that causes COVID-19 than those who had normal levels of vitamin D. Another study found high rates of vitamin D deficiency in people with COVID-19 who experienced acute respiratory failure.

However, at this point, there is not enough data to recommend the use of vitamin D to prevent or treat the virus, according to the National Institutes of Health.

“Researchers did some small observational studies that showed an inverse association between vitamin D levels and COVID-19, meaning the lower the vitamin D levels, the higher the COVID-19 cases,” says UNC Health family medicine physician Sarah Ruff, MD. “But common risk factors for both COVID-19 and vitamin D deficiency are age and obesity.”

In other words, vitamin D deficiency is more common in people who are older and people who have a body mass index of 30 or higher (obesity), and these factors also increase the risk of severe COVID-19 symptoms.

“There’s no clear evidence that vitamin D supplementation would decrease your risk or the severity of COVID-19,” Dr. Ruff says. “That being said, regardless of COVID-19, everybody should make sure that they’re getting enough vitamin D.”

That’s because vitamin D supports the immune system by fighting off harmful bacteria and viruses in addition to helping with bone health. Vitamin D also:

  • Helps regulate how much calcium is in your bloodstream, which helps with heart function, among other roles
  • Corrects mineral imbalances to keep your kidneys healthy
  • Improves muscle function
  • Keeps nerves and nerve receptors healthy to encourage good brain-body communication
  • Reduces inflammation

Dr. Ruff says you should try to get 800 to 1,000 units of vitamin D per day. So how do you do that? She offers three tips for boosting vitamin D:

1. Spend some time in the sun every day.

The most natural way to get vitamin D is with sunlight. Brief exposure to the sun without sunscreen—15 minutes daily—is the most efficient way to spur the production of vitamin D in the body.

“Vitamin D is actually produced in our bodies,” Dr. Ruff says. “The sun’s energy turns a chemical in your skin into vitamin D, and that goes into the liver and then the kidneys, where it becomes active and your body can actually use it.”

Although sun exposure increases your risk of skin cancer, Dr. Ruff says the recommended time per day needed to get adequate vitamin D is probably not enough to cause skin cancer.

“Now that we’re all very worried about skin cancer, we don’t get the sun like we did in the olden days, and in order to get the vitamin D activation from the sun, you have to have bare arms, bare face and no sunscreen for 15 minutes a day,” Dr. Ruff says.

2. Eat lots of eggs and fish.

If spending time in the sun is not an option, you can try to get vitamin D through your diet, though it’s nearly impossible to get an adequate amount through diet alone. Egg yolks and some types of fish contain vitamin D. Salmon is the best choice, Dr. Ruff says.

“If you just wanted to get it naturally from fish and egg yolks, you have to eat a ton,” Dr. Ruff says. “One egg yolk is only 20 units. To get 400 units from fish, you’d have to have a 5-ounce salmon, 7 ounces of halibut, 30 ounces of cod or two 8-ounce cans of tuna every day.” That’s obviously not feasible.

Although there are other ways to get vitamin D through our food, such as fortification in milk and cereals, each serving is typically about 100 units. So even if you get 100 to 400 units a day from the foods that you eat, that’s not enough.

3. Take a vitamin D supplement.

“Most patients should take a vitamin D supplement, especially in the winter,” Dr. Ruff says.

Dr. Ruff recommends vitamin D3, because that’s the kind the human body naturally makes. Vitamin D3 is animal-derived, whereas vitamin D2 is from plants. Both can help increase vitamin D levels in your body.

Also, don’t take more than the recommended amount.

“It is a fat-soluble vitamin, which means if you take too much of it, you can’t urinate it out like a water-soluble vitamin, so it can build up in your fat in your body if you have too much,” Dr. Ruff says. “And it can cause toxicity (meaning it can make you very sick).”


Think you may have a vitamin D deficiency? Talk to your doctor or find one near you.

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