Recent research suggests that vitamin D deficiencies — suffered disproportionately by African Americans — may worsen COVID-19 outcomes. The question is: Why?
Andi Fielder was prescribed high doses of vitamin D to relieve symptoms of multiple sclerosis in 2017. She became an advocate for vitamin D when she learned that as an African American she was predisposed to vitamin D deficiency.
“I’m a big vitamin D advocate,” the 37-year-old Coloradan said. “It’s a big problem with Black people in the US, because we don’t have enough sun.”
Recent research indicates that a deficiency in vitamin D, known for its potential physical and mental impacts, may also increase the likelihood of worsened COVID-19 symptoms, particularly for African Americans, like Fielder.
Dr. David Meltzer, director of the Center for Health and the Social Sciences at the University of Chicago and one of the foremost researchers on vitamin D-related outcomes for African Americans with COVID-19, said that studying vitamin D is a “wildly complex system.”
His 2021 study found that African Americans with extremely low levels of vitamin D (20 ng/mL or lower) were 164 percent more likely to test positive for COVID-19 than those with vitamin D levels of 40 ng/mL or above. But to Meltzer, the reasons behind this correlation are still uncertain.
“We don’t know that the vitamin D levels themselves are always associated with a degree of protection [from COVID-19] yet,” Meltzer said. “One of the complexities in these observational studies is what else could be going on other than the levels you’re measuring.”
Fielder believes that increased vitamin D intake may have strengthened her immune system and prevented infection.
“COVID has capitalized on a weak population,” Fielder says. “I have not had COVID — and I’m in school systems where people have had it — because my vitamin D levels are decent.”
Vitamin D deficiency is a global public health concern, according to researchers at the University of Puerto Rico. It affects 41 percent of Americans, and of those an estimated 76 to 86 percent are African American.
While it might be difficult to determine the exact links between darker skin color, vitamin D, and COVID-19 given the available data, researchers have determined why African Americans suffer from vitamin D deficiencies.
“African Americans are more likely to be vitamin D deficient because of melanin in their skin,” said Dr. Bess Dawson-Hughes of the Jean Mayer USDA Human Nutrition Research Center on Aging’s Bone Metabolism Lab at Tufts University, in Boston.
Melanin is a pigment in the skin, hair, and eyes that determines skin color depending on its type and levels in the body. Ninety percent of the body’s vitamin D is produced in the skin through UVB exposure. While it defends against cancer-causing ultraviolet A (UVA) rays by preventing sunburn, it also prevents the skin from absorbing ultraviolet B (UVB) rays that produce vitamin D.
Whereas people of all races are able to convert UVB rays to vitamin D, Meltzer said, those with darker skin have higher levels of vitamin D-binding proteins. This prevents vitamin D from being absorbed in large doses, as ancestrally darker-skinned populations had to evolutionarily adjust to sunny southern climates.
Much like melanin naturally protects against sunburn, these binding proteins protect against a vitamin D overdose due to increased sun exposure.
“Black people need more sunlight, like a palm tree,” Fielder said. “Is a palm tree going to thrive in a pine tree world? Not without more sun.”
Dawson-Hughes noted other factors affecting vitamin D levels, like seasons, supplement use, and diet. But along with sun exposure, she added, the other main factor in vitamin D deficiency among African Americans is body mass index (BMI).
As vitamin D deficiency is such a universal problem and the risks of taking a supplement are so low, Dawson-Hughes said it’s safe to start an over-the-counter supplement.
“A given supplement dose or food intake is dependent on and inversely related to BMI,” Dawson-Hughes said. “African Americans, in general, have a higher BMI. That would predict a lower [vitamin] D level in addition to darker skin.”
Ashlee Radney also takes vitamin D supplements — she began four years ago to combat seasonal depression, but it has turned into a steady habit that positively affects her mood and energy levels year round.
“I didn’t realize how important it was to take vitamin D until I moved [to Portland, OR],” said 26-year-old Radney about the city’s cloudy and rainy winters. “I chose to keep taking the vitamins even after the winter months, and I’m really happy with how much more clear-headed I am.”
Recent studies about taking vitamin D supplements to prevent the worsening of COVID-19 symptoms yield conflicting results — to Meltzer, race is the missing piece in some of the more inconclusive studies.
In a 2020 study from Spain, patients treated with vitamin D were 70 percent less likely to be admitted to the ICU, while ICU patients were 70 percent less likely to die. In contrast, a 2021 study from Brazil found that a single high dose of vitamin D yielded no effect on a COVID-19 patient’s outcome.
“There’s statistically significant reductions in bad outcomes of COVID-19 for people given vitamin D, and it goes back to the story of race,” Meltzer said. He added that the data from the latter study didn’t consider Brazil’s racially diverse population, which absorbs vitamin D at differing rates due to varying levels of vitamin D-binding protein in their systems.
“I don’t think vitamin D-binding protein is a bad thing, and it’s not that you want to reduce it,” Meltzer said. “You want to give vitamin D the right way for your physiology regardless of what your binding protein is.”
Elizabeth Duran, who is African American, began taking a multivitamin with added vitamin D after researching cures for wintertime fatigue. The 26-year-old New Yorker was unaware of her predisposition to vitamin D deficiency.
“By and large, I see doctors so infrequently,” Duran said. “It’s only so surprising that vitamin D hasn’t been a staple of discussion.”
“I know that African Americans have a jaded relationship when it comes to the health field,” Radney said. “A lot of dark history and current aggressions, which keeps many of us at bay from being properly checked up regularly or educated on our health.”
As vitamin D deficiency is such a universal problem and the risks of taking a supplement are so low, Dawson-Hughes said it’s safe to start an over-the-counter supplement.
“I don’t think it’s cost-effective to get bloodwork done,” Dawson-Hughes said, as vitamin D tests cost between $76 and $400. “And most people who are in the insufficient range don’t usually get symptoms.”
“When you’re getting no effective sun exposure, take [20–25 micgrograms] per day.”
