WASHINGTON--Melanin protects darker skin from premature aging and UV rays, but its protection increases the risk of other diseases, according to research presented this month. The body naturally produces vitamin D - a nutrient known for keeping bones strong - when skin is directly exposed to UV rays from the sun.
However, since melanin blocks those UV rays, it also inhibits vitamin D production in the body, says Dr. Valerie D. Callender, Associate Professor of Dermatology, Howard University.
This may explain why several studies report that anywhere from 36 to 97 percent of African-Americans have low levels of vitamin D. Poor dietary intake of vitamin D from dairy, given the prevalence of lactose-intolerance in the black community, also plays a role.
But, the importance of vitamin D does not end at brittle bones, rickets and osteoporosis.
New research reveals a link between the more common type of breast cancer in African-American women, triple-negative breast cancer, and low vitamin D levels.
Last month, a small study of 89 New York Giants players showed that players with lower Vitamin D levels were more likely to be injured. Over 90 percent of the African-American players were vitamin D deficient, with levels lower than white players who were also deficient.
A 2008 study tied low vitamin D levels to an overall increased chance of early death.
"Vitamin D levels in the blood are associated with prostate, colon and breast cancer," says Dr. Rick Kittles, Director of the Institute of Human Genetics at the University of Illinois at Chicago. "But, we don't know the mechanism."
Understanding its importance, Kittles now performs research on the connection between vitamin D and prostate cancer. He and his team are recruiting both white and black men with plans to collect data on their diets, skin color, sunlight exposure and specific genetics.
The body also uses vitamin D for specific daily functions. According to the NIH, the immune system needs the nutrient to appropriately fight off bacteria and viruses. Nerves also need it to effectively carry messages between the brain and the rest of the body. Without it, the body cannot absorb calcium.
Latrice Landry, researcher at Tufts University's Friedman School of Nutrition Science and Policy, says UV absorption can greatly differ based on skin color.
"Though someone with pale skin can get adequate vitamin D by exposing their arms and legs to the sun for 10 to 15 minutes twice a week in the summer, someone with the darkest skin might need two hours of exposure each time," she adds.
Dr. Wendy Roberts, a dermatologist who specializes in ethnic skin of color and geriatric dermatology, has had similar observations.
"Many African-Americans live and work in the sunbelt, and while [they are] not outdoor tanning, they experience the same UV exposure that whites do while doing their daily activities," she points out.
Yet, there is still a disparity in who develops vitamin D deficiency.
While sunscreen blocks some UV rays, skipping sunscreen to boost vitamin D production is not advised given the well-proven risk of skin cancer.
"For optimal health, I would recommend a vitamin D supplement, especially for anyone, not just African Americans, living in cold climates," says Landry. "Other suggestions are to eat foods fortified with vitamin D."
The daily amount of vitamin D each person needs differs by age, ranging between 400 and 800 IU. Multivitamins typically only have 400 IU, so additional supplements are often needed.
Fatty fish like salmon and tuna are the best dietary forms of vitamin D. The U.S. milk supply is fortified with vitamin D, however, products made from milk, like cheese and ice cream, are not. Other foods have vitamin D artificially added like certain cereals and orange juice.