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.
Supplements of vitamin D can prevent rickets, but the authors say giving vitamin D to mothers cannot raise the level of vitamin D in breast milk enough to prevent the condition. They therefore recommend giving vitamin D supplements in liquid form to babies at risk.
"We support breast-feeding as the ideal nutrition for babies and children but recommend supplementation of all dark-skinned, breast-fed infants and children with 400 IU of vitamin D per day, starting at least by two months of age," Kreiter and colleagues write.
Holick tells WebMD the study should not discourage black mothers or others with dark skin from breastfeeding.
"[Women] need to be aware of this minor issue and deal with it appropriately," he says.
Doctors can diagnose rickets by doing a blood test. Children who have confirmed rickets must be started on high doses of vitamin D immediately and continue to take the supplements for as long as they breast-feed. Holick says most babies will recover from rickets in three to six months, but some permanent damage, such as bowed legs, may require surgery. Once children start drinking whole milk they can usually stop taking the vitamin, but if they have milk allergies or reduced exposure to sunlight, it may be reasonable for them to take it for the rest of their lives, he says.
Robert P. Schwartz, MD, a co-author of the study, tells WebMD that all babies who are exclusively breast-feeding should be taking a daily multivitamin that contains the recommended daily amount of vitamin D needed to prevent rickets.