Three-quarters (45%) of U.S. teens and adults are deficient in vitamin D, also :
Vitamin D insufficiency is more prevalent among African Americans (blacks) than other Americans and, in North America, most young, healthy blacks do not achieve optimal 25-hydroxyvitamin D [25(OH)D] concentrations at any time of year. This is primarily due to the fact that pigmentation reduces vitamin D production in the skin.
Three-quarters (45%) of U.S. teens and adults are deficient in vitamin D, also :
Vitamin D deficiency also leads to low testosterone as it's a precursor for it.