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September 17, 2020

Could Vitamin D Help Protect Against COVID-19?

Could Vitamin D Help Protect Against COVID-19?

Updated on August 5, 2020 at 3:00pm EDT.

As the timeline for an effective coronavirus vaccine remains uncertain, the search for preventive strategies and treatments for COVID-19 is more urgent than ever.

One tantalizing candidate: vitamin D.

There is some evidence to suggest that healthy vitamin D levels are linked to better outcomes among those with COVID-19. The jury is still out on whether or not vitamin D could actually have a protective effect against the disease but the more we understand about this essential nutrient, the more we understand why it might help.

Foods with vitamin D
You may be surprised to learn that vitamin D isn’t actually a vitamin. It’s what’s called a prohormone—a substance the body converts to a hormone.

And unlike other vitamins, such as C and A, which are readily found in a wide range of fruits and vegetables, only about 10 percent of the vitamin D you need comes from food. In fact, it’s found only in small amounts in relatively few food sources, including fatty fish, such as tuna, salmon or sardines, and some dairy products, including egg yolks and cheese.

Milk, orange juice and other fortified foods and beverages provide most of the vitamin D in the American diet.

The role of the sun
With some help from the sun, your body makes most of the vitamin D it needs. Its production is triggered when the sun’s ultraviolet (UV) rays hit your skin. This is why the time of year, where you live, your skin tone, age and use of sunscreen and sun-protective clothing could all affect your vitamin D levels.

“If you’re living north of Atlanta, you’re far enough from the equator that you usually are not going to get enough vitamin D from routine exposure to sunlight,” says Joseph A. Aloi, MD, a professor of endocrinology and metabolism at the Wake Forest School of Medicine in Winston-Salem, North Carolina.

“You need 15 to 20 minutes a day of what I say is ‘bathing-suit exposure.’ Most of us aren’t getting that out gardening in hat and sleeves,” Dr. Aloi adds.

Moreover, dark-skinned people do not make as much vitamin D from sunlight exposure as fair-skinned people, Aloi notes. The melanin in dark skin blocks harmful UV rays, providing protection against sun damage and skin cancer but allowing for less vitamin D production.

People who cover more skin with clothing also make less vitamin D. Older people may be deficient as well because skin doesn’t make vitamin D as efficiently over time. Those who are obese may not get enough because body fat may prevent some vitamin D from getting into the blood. And, perhaps unsurprisingly, deficiencies are more widespread during the darker, shorter days of winter.

Due to concerns about skin cancer, the American Academy of Dermatology still recommends against using sun exposure to obtain vitamin D, advising instead that people get enough from their diet and supplements.

Vitamin D’s possible benefits
Many people link vitamin D to strong bones. It does help the body absorb calcium, which helps build and maintain bones. But its benefits don’t end there. Vitamin D also promotes calcium absorption in the intestines and allows the kidneys to control blood calcium levels as well. It plays a role in cell growth and muscle strength and also helps support the immune system and ease inflammation.

On the flip side, vitamin D deficiency has been linked to a variety of health issues. These include mood disorders, as well as bone conditions, diabetes, obesity, multiple sclerosis, heart disease and being at greater risk for infection.

In children, vitamin D deficiency can result in soft bones—a rare disorder called rickets. In adults, vitamin D deficiency can lead to osteomalacia, or the softening of bones.

Low levels of vitamin D may also lead older people to develop weak or brittle bones that break more easily—a condition called osteoporosis.

What about COVID-19?
Generally, vitamin D could reduce the risk of upper respiratory viral infection. It supports the production of antimicrobial proteins in the cells lining the respiratory tract. It also helps regulate the body’s inflammatory response to infection.

These beneficial properties have led some experts to suggest that taking vitamin D supplements during the pandemic could have a protective effect against COVID-19.

A June 2020 study published in the American Journal of Infection Control found that death rates from COVID-19 are lower in areas closer to the equator, where ultraviolet light is most intense and where the body can most readily produce vitamin D.

But the relationship between vitamin D is still not clear and remains under investigation. Other studies have found a variety of sometimes conflicting results.

Larger, more well-designed studies should help shed light on the topic over time.

How much do you need?
There is still a lot we don’t know about vitamin D, including exactly how much people need to get on a daily basis, according to Aloi.

“We’re really not sure what a normal serum vitamin D level is for optimal health,” he says.

Just as specialists disagree on whether sun exposure is advisable, there is also disagreement about optimal levels of vitamin D in the bloodstream. That’s in part because methods and precision vary from one lab to another.

“The question is whether the serum vitamin D blood level is an adequate measure of total body vitamin D,” Aloi explains. For that reason, he says, “our lab doesn’t list vitamin D as normal or abnormal. They list it as ‘sufficient’ or ‘insufficient.’”

In general, levels below 12 nanograms per milliliter (ng/mL) are too low for bone or overall health. Levels above 20 ng/mL are sufficient for most people, and levels above 50 ng/mL are probably too high.

For most purposes, Aloi says, “the range I’m looking for is 30-50, so that we don’t overshoot. With that, I think we’ve optimized bone health and probably everything else falls into place.”

Should you supplement?
It’s still unclear if taking a vitamin D supplement will help protect otherwise healthy people against COVID-19.

Routine supplementation with vitamin D alone has also not been shown to prolong life or cut the risk for heart disease or cancer. There are currently several trials underway to determine if taking vitamin D alone or with calcium could help reduce the risk for fractures.

Trials assessing the possible benefits of vitamin D supplements for the management of depression, fatigue, arthritis and chronic pain have been disappointing.

And when it comes to vitamin D, more is not necessarily better. Excess amounts could lead to high calcium levels in the blood or urine, kidney stones, calcifications in the body’s soft tissues and damage to the heart or kidneys.

Warning signs of vitamin D toxicity include:

  • Weight loss
  • Excessive urination
  • Abnormal heart rhythms

For people using over-the-counter vitamin D supplements as directed, however, the risk of toxicity is low, Aloi notes.

“My general recommendation for patients,” he says, “is that if you’re taking 2,000 international units (IU) per day of vitamin D, which you can easily get over the counter, you are unlikely to take too much.”

Medically reviewed in August 2020.

Sources:
Medscape. “Low Vitamin D Linked to Increased COVID-19 Risk.” Updated July 2020.
Anthony W Norman. “From vitamin D to hormone D: fundamentals of the vitamin D endocrine system essential for good health.” The American Journal of Clinical Nutrition. Volume 88, Issue 2, August 2008.
Hormone Health Network. “Vitamin D.” Updated November 2018.
U.S. Office of Dietary Supplements. “Vitamin C.” Updated December 2019.
U.S. Office of Dietary Supplements. “Vitamin A.” Updated February 2020.
U.S. Office of Dietary Supplements. “Vitamin D.” Updated March 2020.
Guo J, Lovegrove JA, Givens DI. “A Narrative Review of The Role of Foods as Dietary Sources of Vitamin D of Ethnic Minority Populations with Darker Skin: The Underestimated Challenge.” Nutrients. 2019;11(1):81. Published January 3, 2019.
American Academy of Dermatology. “Vitamin D.”
The National Multiple Sclerosis Society. “Vitamin D.”
Mitchell F. “Vitamin-D and COVID-19: do deficient risk a poorer outcome?” The Lancet Diabetes & Endocrinology. 2020;8(7):570.
Whittemore PB. “COVID-19 fatalities, latitude, sunlight, and vitamin D.” [published online ahead of print, 2020 Jun 26]. American Journal of Infection Control. 2020.
Ali N. “Role of vitamin D in preventing of COVID-19 infection, progression and severity.” [published online ahead of print, 2020 Jun 20]. Journal of Infection and Public Health. 2020;S1876-0341(20)30531-1.
Yao P, Bennett D, Mafham M, et al. “Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis.” JAMA Network Open. 2019;2(12):e1917789.
LeFevre ML, LeFevre NM. “Vitamin D Screening and Supplementation in Community-Dwelling Adults: Common Questions and Answers.” American Family Physician. 2018;97(4):254-260.

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