The results of a study reported at the American Association of Cancer Research's Fourth Annual Health Disparities Conference reveal a need for vitamin D among African-Americans that is far greater than the current recommendation of 600 international units (IU) per day.
In research funded by the United States Department of Defense and the National Cancer Institute, Adam Murphy, MD, of Northwestern University Feinberg School of Medicine, along with Rick Kittles, MD of the University of Illinois, analyzed serum 25-hydroxyvitamin D levels of 492 men aged 40 to 79 who resided in the Chicago area. Skin melanin levels, sun exposure and vitamin D intake were determined, and body mass index was calculated.
Sixty-three percent of African-American men were found to be deficient in vitamin D with levels of less than 20 nanograms per milliliter, in contrast with 18 percent of the Caucasian participants. In addition to African heritage, having a high body mass index and failing to supplement with the vitamin were associated with deficiency. When 30 nanograms per milliliter was used as the cutoff point, the incidence of deficiency rose to 93 percent for African-Americans and 69.7 percent of Caucasian subjects.
"This study shows that the current one-size fits all recommendations for 600 International Units (IU) of vitamin D don't work," stated Dr Murphy, who is a clinical instructor in urology at the Feinberg School of Medicine. "Skin color and sunlight exposure need to be considered for recommended daily allowances of vitamin D."
"It takes a dark-skinned male like myself 90 minutes three times a week to absorb enough sunlight to produce the recommended amount of vitamin D compared to just 15 minutes three times a week for a Caucasian male," he noted. He recommended that men increase their level of vitamin D supplementation if they live in the northern third of the United States "from Northern California all the way to Virginia," and remarked that African-American men residing in Chicago would need to consume 2,500 IU of the vitamin per day to attain normal levels.
"When vitamin D levels in the bloodstream are less than 20 nanograms per milliliter the bone starts to become brittle in adults and in kids it causes rickets," he observed. "This study shows that across the board vitamin D recommendations just won't work for everybody . . . With so many diseases linked to low levels of vitamin D, we should have more stratified recommendations to consider groups within the population instead of making monolithic suggestions."
"Because we have a lot of special populations in the United States – people who have darker skin, people who cover their skin for religious reasons and people who live in poor sunlight environments – there shouldn't be uniform vitamin D recommendations for the entire population," he concluded.