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Interest in vitamin D growing in the age of COVID-19

A critical nutrient for immune system health, outdated fears of dietary cholesterol have steered Americans away from healthy sources of Vitamin D in animal foods and toward supplements, while the need for sheltering indoors has reduced everyone's sun exposure during the pandemic. COVID-19 has only raised the stakes for a widespread vitamin D deficiency in population health.

Vitamin D supplements spill out onto a table
Study shows connection between low levels of vitamin D and chronic inflammation
Oleg Dudko / Dreamstime / TNS

ROCHESTER, Minn. — Thanks to its potent anti-inflammatory and immune system properties, vitamin D has become a supplement of high interest during the COVID-19 pandemic.

A hormone created from exposure to sunlight — or after eating dairy, eggs, fish, mushrooms or organ meat — the body will make enough vitamin D without dietary supplements.

Thanks to poor diets and lack of sunshine, however, deficiencies abound.

Fortunately, you can test for vitamin D levels, as it is believed that over 40% of the U.S. population is lacking in the nutrient. That's especially true among the elderly.

Because the nutrient is stored in fat, body fat can sequester it from use. That has led to even greater deficiencies among those with obesity. Drugs for indigestion and constipation lower vitamin D as well.

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Some of the highest rates of vitamin D deficiency occur among women in the Middle East and North Africa, where ample sunshine cannot overcome cultural practices of covered dress, desert sun avoidance, and the use of sunblock.

Melanin is good for blocking UVA radiation at equatorial zones but can be a liability for persons of color in northern climates. Caucasian persons need 10 minutes in the noonday sun to get enough vitamin D, but Blacks living in sun-deprived parts of northern America need 20 to 25 .

Fifteen- to twentyfold deficiencies of vitamin D among people of color living in northern latitudes have posed a concern for health officials.

The hormone is needed to absorb calcium, making it critical to cardiovascular health. This has led some to believe vitamin D deficiency could be linked to higher rates of asthma and other forms of chronic illness among Black Americans.

Outdated fears of dietary cholesterol have steered Americans away from healthy sources of vitamin D in animal foods, while the need for sheltering indoors has reduced everyone's sun exposure during the pandemic. COVID-19 has only raised the stakes for vitamin D deficiency in population health.

A JAMA Network Open study published in March 2021 found that Black individuals deficient in vitamin D had over two and a half times the rate of COVID-19 infection as did Black individuals with sufficient levels.

Last fall, researchers in England reported that vitamin D deficiency doubled the odds of hospitalization from the virus.

Globally, a separate study has learned that 16% of a country's COVID-19 mortality can be predicted by its latitude, with death from the illness rising as you move farther from the equator.

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These factors and others have some asking whether supplementing vitamin D — often at very high levels — is a safe and effective way to protect yourself from COVID-19.

For now, the answer is no. That's because, besides not having been shown as effective, many believe that excess vitamin D may cause the body to form kidney stones.

Can vitamin D be protective against COVID-19?

The natural way to get vitamin D is through animal foods or sunshine. Supplements at low doses are beneficial, but a deficiency identified during testing can sometimes benefit from medically supervised high dose supplementation.

At the start of the pandemic, health officials in England offered free supply of low dose vitamin D — 400 International Units (IU) daily vitamin D to all residents at risk of poor outcomes. Whether such supplementation helps stave off severe COVID-19 has been hard to establish, however.

Its uses in disease prevention are unproven. Last year, a team of Harvard researchers reported the results of VITAL, a 5-year, 25,000-person trial of 2,000 daily IU of vitamin D for reducing incidence of cancer or heart attacks. Those results came back negative.

Nor has the best evidence established that taking vitamin D in high quantities is effective in treating COVID-19. That was the finding in February 2021, when a group of Brazilian researchers writing in the journal JAMA reported on mega-dosing vitamin D in patients hospitalized with the virus.

The researchers found that giving sick COVID-19 patients 200,000 IU of vitamin D — 300 times the recommended daily intake — had no effect on length of stay, mortality, or other clinically important outcomes.

"So far there has been insufficient evidence for the Centers for Disease Control and Prevention to recommend either for or against vitamin C or D in the treatment or prevention of COVID-19," said Mayo Clinic urologist Dr. Kevin Koo. "In some cases, studies (of the vitamins) were stopped early due to the apparent futility of these treatments in patients with COVID."

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The public remains attracted to the perceived advantages of so-called "natural" measures conferred by aggressive use of dietary supplements, and that's making some doctors frustrated.

"I'm telling you. Vitamin C and D 'MEGADOSING' is causing so many stones right now," is how Dr. Ashley Winter recently put it on Twitter. "I'm tired. Everyone stop it!"

A Board-certified urologist practicing in Portland, Oregon, Winter drew over 900 replies to the post. The tweet was accompanied by a lengthy explanation of how too much vitamin D can cause hypercalciuria, a condition capable of leading the body to form kidney stones.

"I am not against high ...dosing in vitamin D deficiency with medical oversight," Winter wrote. "But don't take high doses for 'IMMUNE BOOSTING.'"

The replies grew heated at times, and included that of an Italian researcher who had recently learned those with a nutrient deficiency can tolerate the 600,000 IUs of vitamin D over three months.

Vitamin D supplementation and kidney stones: real?

Though it's clear it raises calcium in your urine, the data are mixed on whether taking higher amounts of vitamin D will give you kidney stones.

The Recommended Daily Allowance for vitamin D is 600-800 IU daily, and Mayo Clinic says adverse effects are possible at over 4,000 IUs daily. That said, supplement vendors offer bottles of vitamin D gel tablets containing from 5,000 to an eye-popping 50,000 IUs a dose.

Koo, an expert on the use of supplements and kidney stones, says Mayo is seeing more cases of patients presenting with the calcifications, but does not attribute them to any one cause.

"Vitamin D (is a) part of metabolic pathways that regulate calcium," he says, and large concentrations "can substantially increase levels of calcium in bloodstream and urine."

"Having excess vitamin D and consequently excess calcium circulation in the bloodstream and urine can lead to the urine being saturated with calcium, which can increase the risk of calcium stone formation."

"We've been very busy in our department since the initial wave of the pandemic," Koo said, "and the volume of patients who have been coming to Mayo Clinic for kidney stones has been no exception."

Though he says patients coming in "do appear to have complex stones or larger stones," he believes the issue could be due to a combination of factors including delayed care, changes in diet and possibly taking supplements like vitamin C or D in response to the COVID pandemic.

"Some patients have reported taking more dietary supplements or vitamins during the pandemic," he said, "but it's hard to say whether this has led to ... new stone formation or accelerating stone occurrence ... it's difficult to pinpoint one specific reason, and most likely it's a combination of factors."

"Sometimes our patients may think that if some is good, more must be better," Koo says. "But in fact we know that in the cases of patients who are at risk of forming kidney stones, excess doses of vitamin C and D may increase their risk unnecessarily."

Related Topics: CORONAVIRUS
Paul John Scott is the health reporter for NewsMD and the Rochester Post Bulletin. He is a novelist and was an award-winning magazine journalist for 15 years prior to joining the FNS in 2019.
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