is an essential nutrient, which means the human body needs it but can’t make it on its own.
While some foods such as salmon and dairy contain (or are fortified with) vitamin D, human beings get most of their vitamin D from the sun, through a chemical reaction in the skin that produces vitamin D.
Black people have higher amounts of melanin in their skin than those with lighter skin tones, and melanin naturally provides some protection from the sun, but it also reduces the skin’s ability to produce vitamin D from sunlight.
What’s more, many Black people are lactose intolerant, so our diet often lacks dairy fortified with vitamin D, leaving us with lower than average levels in their system.
Is the Vitamin D Test Wrong?
By the current blood test for vitamin D, most African-Americans are deficient. That can lead to weak bones. So many doctors prescribe supplement pills to bring their levels up.
But the problem is with the test, not the patients, according to a new study.
The vast majority of African-Americans have plenty of the form of vitamin D that counts — the type their cells can readily use.
“The population in the United States with the best bone health happens to be the African-American population,” says Dr. Ravi Thadhani, a professor of medicine at Massachusetts General Hospital and lead author of the study. “But almost 80 percent of these individuals are defined as having vitamin D deficiency. This was perplexing.”