Photo: Richard Chance

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Deneen Sherrod knew something wasn’t right. “I was having pain in my joints, and I was aching all over,” said the 56-year-old IT specialist who lives near Baltimore. A two-time breast cancer survivor, Sherrod saw her doctor right away. Tests for lupus, Lyme disease, and rheumatoid arthritis all came back negative.

Then the results of her blood panel came back. “She said, ‘Your vitamin D is severely low,’” said Sherrod, who is Black. She was surprised when D2 supplements eased her pain. “I was like, really? Vitamin D [deficiency] is going to be causing pain like this?” she said. “At first I didn’t believe it because I had never heard that before.” She’d thought only babies needed vitamin D supplementation for bone development.

For more than 100 years, conventional medical wisdom held that people only needed the “sunshine vitamin” for building healthy bones and avoiding diseases like rickets. It doesn’t take much vitamin D to do that, and for some people, that’s where vitamin D’s usefulness ends. For other people, however, the standard vitamin D recommendations are insufficient and can result in serious health consequences.

Though a handful of large vitamin D supplementation studies have had inconclusive results, scientists now can point to many studies demonstrating that vitamin D has wide-ranging health effects. Supporting immune function and preventing chronic, nonskeletal diseases seems to demand a higher blood level of vitamin D. “There has been an explosion of data about the adverse consequences of vitamin D deficiency,” said Walter Willett, MD, Ph.D., professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health. Willett points to a slew of studies linking low vitamin D status with a higher risk for breast, prostate, and colon cancers as well as Type 2 diabetes, multiple sclerosis, low birth weight, and dementia — conditions that also disproportionately affect Black Americans.

If you’re Black or have dark skin, and you don’t take supplements, there’s a very good chance you’re deficient in vitamin D. A large 2009 analysis found that 97% of Black Americans and 90% of Latinx people had low vitamin D levels.

Leading infectious disease experts think this chronic vitamin D deficiency has doomed generations of Black Americans to poor health. Scientists in the U.K., Philippines, and U.S. have written papers identifying vitamin D deficiency as a possible underlying risk factor for severe cases of Covid-19, which has killed Black Americans at about three times the rate of white people.

These experts, including Bruce Hollis, Ph.D., who has studied the effects of vitamin D for 35 years, think making sure more Black people are vitamin D replete could be life-changing. “The Black population in northern latitudes suffer incredible health disparities which include hypertension, diabetes, obesity, cancer, and birth complications,” Hollis, of the Medical University of South Carolina (MUSC) said via email. “I and others believe that a major factor underlying all of these afflictions is a lifelong chronic deficiency of vitamin D. If this one thing, vitamin D deficiency, could be corrected in the Black population, [many] of the health disparities they are currently experiencing could be largely alleviated.”

While poor access to medical care plays a role, Hollis isn’t alone. “If you went on a campaign for sufficiency, I think a lot of the disparities would decrease,” said Adam B. Murphy, MD, an assistant professor of urology and preventative medicine at Northwestern University in Chicago whose research found that low vitamin D levels increased prostate cancer aggressiveness. “Increased incidence and increased aggressiveness I believe would improve.”

How Much Vitamin D Is Enough?

The Endocrine Society, which issues guidelines for doctors, recommends a vitamin D blood level of 30 ng/mL for good health. Levels of 21 to 29 are called insufficient while 20 or under is deficient. The Endocrine Society advises that people who are deficient may need to take 1,000 to 2,000 IU daily to reach the target level. If people are obese, the group recommends 6,000 to 10,000 IU daily to get their blood level up to 30 ng/mL because fat binds with vitamin D, so there’s less in the bloodstream.

They also recommend that people at high risk, including Black Americans and Latinx people, get screened for deficiency, and that adults in these groups who are deficient take 50,000 IU of vitamin D per week, or 6,000 IU daily, for eight weeks to catch up.

That catch-up prescription is typically vitamin D2. It comes from plants, and it’s used to fortify foods. D3 comes from animal sources, like fish oil, and it’s available over the counter.

But here’s where things get complicated. The National Academy of Medicine (NAM) is a private nonprofit think tank designed to provide unbiased recommendations to the U.S. government. Its mission includes “improving health equity.” When the Food and Nutrition Board of this organization (then called the Institute of Medicine) set a target for vitamin D blood levels in 2011, they chose 20 ng/mL since that’s sufficient for bone health. They determined that 12 to 19 ng/mL is inadequate for bone health while levels under 12 are deficient. To achieve the 20 ng/mL target, they recommend people get at least 600 IU a day from food, sun, and supplements.

The conflict between the two sets of recommendations has created confusion and may leave Black people vulnerable. Indeed, there’s evidence that people who follow the NAM guidelines aren’t getting enough vitamin D. A 2007 study of 40 mostly Black women and their newborns found that even though the women took the recommended 600 IU of vitamin D and drank two glasses of milk daily during pregnancy, 50% were still deficient, and so were 65% of their babies. Another prostate cancer study found that a dose of 4,000 IU a day was required to equalize blood levels in Black and white subjects. In the discussion, the author notes that the federally recommended dose wouldn’t have been enough.

These small studies jive with Murphy’s research, which shows 600 IU a day isn’t enough for Black people. He found that for Black men in Chicago, where he conducts research, even if they were getting that amount, they were still deficient. He believes Black people need at least 2,000 IU of vitamin D a day, period.

Unfortunately, when governing bodies make sweeping public health policies, he says minorities often get shortchanged. “So from the perspective of structural racism, the way we do guidelines, it’s set up so that the general population, which is made up of mostly whites in these studies, leads you to biased results that put others at risk,” he said.

Consider the sweeping U.S. public health recommendation to avoid sun exposure sans sunscreen. It’s designed to prevent skin cancer, which is more common among light-skinned people. Yet, both avoiding the sun and faithfully applying sunscreen may have unintended negative health effects, especially for dark-skinned people. The health recommendation to avoid UV exposure was based on observational data rather than a randomized controlled trial, which would be unethical.

“When it comes to the effect of sunlight and skin cancer, we don’t need a randomized controlled trial to give [white] people advice on that. But if it’s about Black people, we need research,” says Tom Weishaar, Ph.D., a postdoctoral fellow with the Center for Health Equity at Teachers College at Columbia University. “It’s not about people being evil; this is what systemic racism looks like.”

Why Does Vitamin D Matter So Much?

You can get vitamin D from your diet: It’s found in eggs, fatty fish, and fortified milk, yogurt, and juice. And of course, our bodies make vitamin D when our skin is exposed to direct sunlight (hence the nickname “the sunshine vitamin”). If you have pale skin, you can produce a whopping 20,000 IU of vitamin D with just 20 minutes in full sun. Windows block all vitamin D production; so does sunscreen.

Melanin acts like a natural sunscreen, so the more you have, the less vitamin D you make from the sun. So for a dark-skinned person to make the same amount of vitamin D as someone fair-skinned, Willett said they’d need to get about six times as much sun exposure. That simple fact has left Black people, especially in northern latitudes, deficient in this crucial nutrient for generations. “It’s one of the legacies of slavery,” said Willett. When Africans, whose dark skin was perfect for their sunny equatorial home, were enslaved and taken north, many developed diseases like tuberculosis and rickets, both linked to vitamin D deficiency.

Poor health has plagued Black Americans for generations. Even before researchers identified vitamin D, around 1915, they realized that something was causing Black infants in Columbus Hill, a primarily West Indian neighborhood, to die at three times the rate of white babies in New York City. Of the Black children who survived infancy, 90% had rickets, a bone deformity. Clinical nutrition researcher Alfred F. Hess, MD, discovered that cod liver oil, which is rich in vitamin D, could prevent or lessen the chances of rickets; so did exposure to sunlight and quartz mercury-vapor lamps. Hess developed a public health campaign and clinic to supplement babies with cod liver oil in 1917.

As 1.6 million Black Americans left the South seeking a better life in cooler northern cities during the Great Migration, their poor health continued. Researchers noted that in 1910, Black Americans in northern cities died from tuberculosis infections at three times the rate of white people. By 1933, the Black death rate disparity had risen to five times. They blamed this disparity on shared living conditions where disease can spread easily. It seems fitting that a 2006 study led by Philip Liu used tuberculosis bacteria and blood cells from Black Americans low in vitamin D to demonstrate that vitamin D is critical to mounting an effective immune response.

Vitamin D is not actually a vitamin but a steroid hormone that tells cells to do certain things, just like testosterone or estrogen. Most of our cells have vitamin D receptors so they can get signals from vitamin D circulating in our bloodstream. The same way testosterone affects libido, hair growth, energy, and bone strength, vitamin D plays a role in many critical body systems. “It has a rather significant effect on your burden of disease,” or how healthy you are, said Carol L. Wagner, MD, a neonatologist and researcher at MUSC. “If you came up with … this drug that was vitamin D, it would be worth billions.”

Researchers are still discovering ways that vitamin D can improve health for all people. It’s been shown to reduce the chance of acute viral respiratory infections and overall cancer mortality. It’s also shown benefits for reducing the risk of Type 1 diabetes in children, and a 2019 trial found vitamin D supplements increased insulin sensitivity in people who were pre-diabetic or newly diagnosed with Type 2 diabetes. Shani Davis, NP, a diabetes specialist in Tallahassee, Florida, says having sufficient vitamin D levels helps her patients have better outcomes. “It can play a role in inflammation reduction and also decreases their risk for chronic health complications,” which can include amputations and kidney disease, Davis says.

It seems to be critical for pregnant and lactating women, too. Black and Latinx women usually have higher rates of preeclampsia, low birth weight, and gestational diabetes. But when Wagner and research partner Hollis give women enough vitamin D, Wagner says, “the health disparities we see disappear.” Wagner and Hollis did a 2011 controlled trial showing that with vitamin D blood levels of 40 ng/mL, the risk of early delivery dropped by 45% for Black women and 79% for Hispanic women. Another trial established that taking 4,000 IU of vitamin D3 daily was safe for both pregnant women and their fetuses. Wagner said adequate vitamin D intake during pregnancy has the biggest effect on overall health in a child’s first 1,000 days of life.

However, several large trials of whether vitamin D supplementation offers benefits beyond bone health have had mixed results, although some experts question the way these studies were designed. That includes VITAL, a trial of 26,000 people that tracked vitamin D’s effect on cancer, heart disease, and stroke. Overall, the trial found limited benefits to taking 2,000 IU of vitamin D and 1 gram of omega-3 fatty acid daily other than a signal for reduction in cancer deaths and, for African Americans, a 23% reduction in cancer risk. JoAnn Manson, MD, one of the VITAL directors, says other potential benefits are still under study in the trial, but the supplements did not appear to be a magic bullet. She doesn’t believe there’s sufficient evidence that vitamin D supplementation would resolve Black health disparities, though “it may narrow some of them.”

Manson, chief of preventative medicine at Brigham and Women’s Hospital, and a professor at Harvard University, said right now, it’s wise for everyone to take 1,000 to 2,000 IU of vitamin D a day. “I do think there are several lines of evidence that avoiding vitamin D deficiency is important to lower your risk during this pandemic,” she said. But based on her research, there’s no clinical trial evidence to support a public health recommendation that most Americans take more than 600 to 800 IU daily outside of the pandemic.

Murphy, of Northwestern University, agrees — in part. He said large vitamin D studies often fail to show benefits because when the vast majority of study participants are white and not short on vitamin D, giving them more doesn’t help. For example, in the recent D2D Study into the role of vitamin D in diabetes prevention, 80% of the 2,400 subjects already had vitamin D levels of 20ng/mL or more. In hindsight, authors realized that may be why taking 4,000 IU of vitamin D didn’t significantly lower diabetes risk.

When you look at the disease state of Black Americans, especially in northern cities like Chicago, Murphy says you’re seeing the effect of being consistently deficient for generations, which acts as a control. “You need to study these kinds of things in poor UV environments, and you need to enrich the sample for African Americans and dark-skinned people so you can find the associations better,” he said.

Aside from his role at Northwestern, Murphy works part time at Chicago’s Cook County Hospital and the local VA hospital, so he has access to a large pool of Black subjects. “I’m always trying to focus on Blacks and Hispanics and how we bring them along,” he said. “It’s worth it, but it’s not easy.”

What Needs to Change?

Murphy believes it’s high time for clinical studies and nutritional recommendations to be tailored to the specific needs of vulnerable minority populations. Jewel L. Crawford, MD, an assistant professor of preventive medicine and community health at Morehouse School of Medicine, points to the widely criticized Body Mass Index as an example. A decade ago, it became clear that BMI measures developed using white people were overestimating obesity in Black people, who often have denser bones or more muscle. The Endocrine Society suggested race-specific measures for healthy body weight and composition.

Policy changes are needed to drive an increase in Black Americans’ vitamin D levels. “The policy can influence the individual behavior,” said Crawford, who studies social determinants of health. Public health campaigns could raise awareness of the importance of having a healthy vitamin D level, along with exercise and a diet rich in green vegetables and fruit, she says. Many Black people are lactose intolerant, so they don’t drink much milk. And while vitamin D is relatively affordable, with a typical bottle of 200 capsules costing $10, it’s not in the budget for many Americans. Currently, the country’s two main nutrition assistance programs — SNAP and EBT — can’t be used for any supplements. If that changed, people in those programs could pick up D3 capsules, along with fortified orange juice and yogurt, at the grocery store.

Still, Crawford notes that being replete with vitamin D won’t erase the effects of chronic stressors like living in a violent neighborhood, being exposed to pollution, or “looking over your shoulder for the police and being anxious walking around, just living while Black.”

Murphy said to erase the health disparities for Black and Latinx people, more funding is needed for studies targeted on minority health. That especially makes sense as the demographic mix in the US shifts. It’s estimated that for people under 18, whites are already a minority. By 2045, the U.S. Census Bureau predicts that the U.S. will be majority minority.

And checking vitamin D levels should be routine for primary care providers, Murphy says.

As for Sherrod, she says taking vitamin D supplements resolved her joint pain. But with elective procedures on hold during the pandemic, Sherrod is still waiting for another biopsy to see if her breast cancer has come back again. She wonders why her doctor never mentioned vitamin D, or checked her level, when she was treated for cancer in 2005 and 2010. “There’s not as much money invested in vitamins as there is in prescription medicine. There are so many commercials on TV advertising medications,” she notes. “Do you see any vitamin D commercials?”

Hollis, the researcher from MUSC, puts it bluntly: “There’s no money to be made. It’s not a fancy drug. It’s basically free. If this was a drug people could make money on, [it would be different],” he says. “I didn’t used to believe in the conspiracy of Pharma to keep these simple things out of the mainstream, but I’m starting to believe it.”