Black, Breast-Fed Babies at Risk for Vitamin Deficiency
Aug. 10, 2000 -- Rickets, a condition that causes the bones of small children to become soft, weaken, and break easily, is rare in the U.S. But several dozen cases of the condition, which is caused by a lack of vitamin D, have popped up among breast-fed black babies, alarming some medical experts. However, experts still emphasize that breast-feeding is best for babies.
The problem appears to be twofold. First, in contrast to formula or store-bought whole milk, which is fortified with vitamins, breast milk contains barely 10% of the amount of vitamin D that children need every day to build strong bones and teeth. Second, much of our vitamin D comes from exposure to sunlight, but dark skin doesn't absorb as much of it as lighter skin.
In fact, having very dark skin is the equivalent of wearing a sunblock with an SPF of about 30, says Michael Holick, MD, PhD.
"Since African-Americans have increased pigmentation in their skin, even if they're exposed to sunlight, their capacity to make vitamin D can be reduced by as much as 95%," he tells WebMD. "Somewhere around 90% of our daily requirement comes from casual exposure to sunlight." Holick is professor of medicine, dermatology, and physiology and director of the clinical research center at Boston University Medical Center.
Holick says excess vitamin D is stored in body fat so that in winter, when sunlight is weakest, the body can tap into its stores to satisfy the daily requirement of vitamin D. But people with the darkest skin may have the lowest stores of the vitamin.
A study in the August issue of the Journal of Pediatrics reports 30 cases of rickets among black babies, all of whom were breast-fed for an average of just over a year. Rickets babies had a variety of bone deformities such as bowing of the legs, flaring of the wrists, broken bones, and growth problems.
"As in other studies, the vast majority of the patients were growth retarded in both height and weight by the time of diagnosis and nearly one third were severely growth retarded," writes Shelley R. Kreiter, MD, and colleagues from Wake Forest University School of Medicine in Winston-Salem, N.C.