Vitamin D is important to the health of every system in the body, and yet many people do not get the recommended amount.
“Many, many Americans — almost half — arevitamin Ddeficient,” saysDavid O. Meltzer, MD, PhD, the chief of hospital medicine at University of Chicago Medicine. “But we know that in excess of three-quarters of people with darker skin, including African Americans and Hispanics, arevitamin D deficient.”
That gap can have some serious health consequences: Researchers are increasingly looking at the link between vitamin D deficiency and a number of diseases, with some research indicating that Black people with vitamin D deficiency have higher incidences of other health problems. There are also some continuing misconceptions and myths about vitamin D and people with darker skin, given the skin’s important role in helping the body generate much of the vitamin D it needs through sunlight.
Read on to learn about vitamin D deficiency, how Black people in the United States are at highest risk, what that means for their health, and how to get enough of the vital nutrient.
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Being Low in Vitamin D Can Pose Health Risks
“Most of us grew up learning aboutthe importance of vitamin Dfor bone health, but it may also play a role in immune system support and a number of chronic health conditions,” saysMarisa Moore, RDN, a registered dietitian nutritionist in Atlanta. Besides helping your body absorb and usecalciumto grow and maintain bone, vitamin D is involved in cell growth and blood sugar regulation. Plus, the functioning of your muscles, nerves, and immune system all get an assist from the nutrient, according to theNational Institutes of Health’s Office of Dietary Supplements (ODS).
A walk in the sun after breakfast may get you on your way to the amount of vitamin D you need for the day. That’s because your body makes a form of the nutrient cholecalciferol(also known as D3) when your skin is exposed to sunlight, according to the ODS.You can also get it from certain foods, such aseggsand fortified milk and orange juice. Other sources ofvitamin D3include fatty fish such as salmon, herring, and halibut; and you can get the plant-based form known asvitamin D2(ergocalciferol) in mushrooms treated with ultraviolet light, says the ODS.
People with mild deficiency typically will not have symptoms, but when the deficiency is more severe, they may show signs such as soft and weak bones, which are hallmarks of osteomalacia (softening of the bones) in adults, and rickets and malformed bones in children, according to the ODS.
Severe rickets can cause pain, seizures, muscle spasms, and developmental delays. Black children who are breastfed without vitamin D supplementation are at especially high risk for rickets, notes the ODS.
Osteomalacia can lead to aches and pain in the lower back, pelvis, hips, legs, and ribs, as well as decreased muscle tone and difficulty walking, according to theMayo Clinic.
Vitamin D also works with calcium to help preventosteoporosisin older adults, a disease that causes bones to lose density and fracture more easily.Post-menopausal womenare at especially high risk forosteoporosis, per the ODS.
Low vitamin D status has also been linked to type 2 diabetes and insulin resistance, according to areview of research. Both conditions are more prevalent among Black people in the United States than in other groups, according to a 2020 report by the U.S. Department of Health and Human Services and the Centers for Disease Control and Prevention (CDC). And although the report noted that a cause-and-effect relationship has not yet been firmly established, a study published in Nutrition & Diabetes in 2022 found additional evidence that Black Americans with normal blood levels of vitamin D had a 35 percent lower risk of diabetes than those with deficient levels.
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Vitamin D Deficiency Prevalence in Black Americans
The answer to how much vitamin D is enough varies among respected standard-setting organizations. It is measured according to the concentration of the pre-hormone 25-hydroxyvitamin D in your blood, as the ODS explains. The ODS’s guidelines advise that adults are:
- Sufficientat levels of 20 nanograms per milliliter (ng/mL) or 50 nanomoles per liter (nmol/L) and above
- Insufficientat between 12 and 20 ng/mL (30 and 50 nmol/L)
- Deficientat levels below 12 ng/mL (30 nmol/L)
Guidelines from theEndocrine Societyraise the threshold of sufficiency to 30 ng/mL (75 nmol/L) and deem anything below 20 ng/mL (50 nmol/L) to be deficient.
Using the Endocrine Society’s higher threshold, up to 42 percent of adults in the United States are deficient, according to ananalysis of datacollected by the CDC. But that vitamin D deficiency rate for Black people was nearly double, at 82 percent, followed by 69 percent of Hispanic people.
Astudydrilled into the risk factors for Black people in the United States and found that fitness and weight were linked to vitamin D status. Black people with moderate or highfitnesslevels were 45 percent less likely to be vitamin D deficient than those with low fitness levels. Meanwhile, Black people withobesitywere 70 percent more likely to have vitamin D deficiency than those of normal weight. The study authors noted prior research linking vitamin D status to somecardiovascular diseases, as well as the role that the nutrient is known to play in skeletal-muscle function. They said more research is needed to determine whether fitness and weight can cause a change in vitamin D status.
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Why Do Black People Have the Highest Risk of Vitamin D Deficiency?
While it’s well known that Black people have the highest rates of vitamin D deficiency in the United States, the reasons may be complex and warrant more study, says Dr. Meltzer.
Melanin is the pigment that provides skin color, and individuals with darker skin have more of it than those with lighter skin. Having more melanin reduces your ability to synthesize vitamin D from the sun, resulting in lower 25-hydroxyvitamin D levels, according to the ODS. Further compounding that can be things like age, clothing that covers up your skin,sunscreen, and seasonal variations in sunlight exposure.
Another factor affecting the amount of vitamin D in your body and how it is used is the presence of vitamin D–binding proteins, which carry the nutrient through your bloodstream to various organs. “There are reasons to believe that African Americans not only need more sun to produce vitamin D, but they could well have different vitamin D–binding proteins that might make them more vulnerable to variations in sunlight,” says Meltzer.
Yet, being “deficient” according to current standards may not have the same health implications for Black people. One large study that focused on vitamin D–binding proteins found that Black participants had lower levels of both vitamin D and vitamin D–binding proteins. Yet, Black people had “levels of bioavailable 25-hydroxyvitamin D that are equivalent to those in whites,” the authors noted. In other words, the lower levels of binding proteins may work in balance with the lower levels of 25-hydroxyvitamin D to allow similar amounts of the nutrient to be available for use by the body, they suggested. “Low levels of total 25-hydroxyvitamin D probably do not indicate true vitamin D deficiency when levels of vitamin D–binding protein are also low, as in many Black Americans,” they said, adding that other factors must be considered when diagnosing vitamin D deficiency, such as whether a person exhibits symptoms.
The study authors further noted that despite being diagnosed more frequently with vitamin D deficiency, Black people have higher bone mineral density and a lower risk of fractures due to fragile bones compared with white people. As the Institute of Medicine noted in its dietary guidelines: “Despite lower serum 25(OH)D concentrations, African Americans have a superior ‘calcium economy’ compared with whites in North America and have less risk for osteoporosis and fracture.”
“It may well be that some people have vitamin D–binding proteins that are better able to release vitamin D when you’re not producing it through sun exposure or not taking it in,” says Meltzer.
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How Vitamin D May Affect the Risk for Other Diseases
In addition to being at higher risk for vitamin D deficiency, Black people in the United States experience higher rates of death and illness than white people from a number of diseases, includingdiabetes, heart disease,stroke, andhigh blood pressure, according to theCDC. TheCOVID-19 pandemicadded yet another disease to that list, withBlack people being hospitalized for COVID-19 at a ratethat was 4 times that of white people and a death rate twice as high, according to theCDC.
One continuing area of focus for researchers ishow vitamin D might affect COVID-19. Meltzer led astudythat examined that relationship in a cohort of 489 patients who had tested positive for COVID-19 at the University of Chicago Medicine. They found that patients with likely vitamin D deficient status (based on their medical records) had a 1.77 times greater risk of testing positive than those who were likely not deficient.
Meltzer notes that a majority of the patients in the cohort were Black. “Since African American and Hispanic populations in the U.S. have both high rates of vitamin D deficiency and bear a disproportionate burden of morbidity and mortality from COVID-19, they may be particularly important populations to engage in studies of whether vitamin D can reduce the incidence and burden of COVID-19,” he and his coauthors wrote.
For now, vitamin D deficiency is only linked to higher COVID-19 risk; no study has proven a cause-and-effect relationship. Research is ongoing to find out if vitamin D can help prevent or treat COVID-19. Still, as Meltzer says, there isn’t yet a “home run” study regarding the association between COVID-19 and vitamin D deficiency. “I think the most important message is that there is a lot we really don’t understand, and there’s a tremendous need for research.”
The National Institutes of Health (NIH) also notes in its guidelines that there is insufficient evidence to recommend either for or against the use of vitamin D for the prevention or treatment of COVID-19.
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How to Take Charge of Your Nutrition and Get AdequateVitaminD
There’s no downside to getting enough vitamin D through food, and minimal risk to vitamin D supplementation at recommended doses. “There are many reasons to work with your healthcare provider to get your levels checked at least once a year and increasevitamin D-rich foodsor supplements as needed,” says Moore. As with all supplements, discuss the possibility of taking a vitamin D supplement with your healthcare team, asking about the benefits versus risks, and whether you can get a blood test to see where your current vitamin D levels are.
Request aVitaminDStatus Test
Your doctor might order a blood test to check your 25-hydroxyvitamin D levels in order to screen for or keep tabs on bone disorders such as osteoporosis, osteomalacia, and rickets, according to MedlinePlus. People with asthma,psoriasis, and someautoimmune diseasesmay also be tested.
As mentioned, you may be diagnosed with vitamin D deficiency if your reading is below 12 ng/mL (30 nmol/L) according to ODS standards, or below 20 ng/mL (50 nmol/L) according to Endocrine Society standards. A low result could indicate that your body is having problems using the nutrient because of kidney orliver disease.
On the other hand, it is possible to havetoo much vitamin Din your blood. According to ODS, a result above 150 ng/mL (375 nmol/) indicates toxic levels, which in turn can result in hypercalcemia, or too much calcium in the blood. Hypercalcemia can cause kidney stones and gastrointestinal problems, bone pain, and muscle weakness, and it can disrupt the functioning of your brain and heart. Very high amounts ofvitamin D supplementsare usually the culprit when your levels are too high, says the agency.
Get More Vitamin D Through Diet and Supplements
“I think that people still widely believe that we get enough vitamin D from sun exposure. But that’s not always the case — especially since we spend most of our time indoors and darker skin tones tend to produce less vitamin D from sun exposure,” says Moore. “There are a fewfoods high in vitamin D, including salmon and sardines, eggs with the yolk, and mushrooms exposed to UV light. You can also get it from fortified foods such as plant milk, cereal, and some orange juice.”
TheODSrecommends that these age groups get the following amounts of vitamin D daily:
- Under age 1: 400 international units (IU)
- Ages 1–70: 600 IU
- Over age 70: 800 IU
And it is difficult to get that much from food alone. Most men take in only 204 IU daily from food and drink, while women take in 168 and children take in 196, according to ODS. Keep in mind that a cup of vitamin D–fortified low-fat milk will give you only 100 IU, per theU.S. Department of Agriculture. Yet when vitamin D supplements are factored in, the average daily intake rises to 796 IU in people ages 2 and older, says the ODS.
In his clinical practice, Meltzer advises everyone to take supplements, regardless of background. Your doctor may disagree on the basis of your individual health, so be sure to ask.
Recommendations vary on how much to supplement, but the Endocrine Society notes that adults ages 19–50 need 600 IU per day but may need 1,500–2,000 IU daily to maintain sufficient levels; infants (0–1 year old) should take at least 400 IU daily; and children (1 to 18 years old) should take 600 IU daily and may need as much as 1,000 IU. To avoid toxicity, the ODS places the upper limit for people over age 9 at 4,000 IU per day and 1,000–3,000 IU for babies and children up to age 8.
“Mostmultivitaminshave about 400 IU in them,” says Meltzer. “People who take them for osteoporosis probably take about 1,000 IU a day.”
Again, consult your healthcare team to determine your vitamin D needs.
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Don’t Completely Avoid the Sun
While it’s nearly impossible to get enough vitamin D from sun exposure, Meltzer says sunlight can add to the diet and supplements to help boost your levels. The longer you can manage it on a daily basis, the better, he says, acknowledging the challenges posed by seasonally cold temperatures and indoor environments, since sunlight passing through glass doesn’t produce vitamin D. At the same time, he cautions that you should avoid sunburn, which is a risk factor for skincancer. Ultraviolet-ray damage from the sun can happen in as little as 15 minutes, according to theCDC, which recommends wearing sunscreen of at least SPF 15 or higher, among other protective measures.
