This I already knew, but the article goes into some detail about why.
Bottom line: The melanin in the skin of people of color does something great: It protects them from harmful UV rays. but it also does something not-so-great: It blocks Vitamin D production.
And since the medical community has evolved from thinking Vitamin D only impacts bone health, but also may lower the risk of diabetes, hypertension and other very common illnesses and conditions, they are thinking that epidemic Vitamin D deficiency is really not a great thing!
The article's bottom line is that it is very very difficult to get enough Vitamin D naturally from either our diet or from foods. They recommend supplements all the way.