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Rickets sheds light on how racial disparities happen

Last spring, Mareana Powell noticed something wrong with her 17-month-old son Jacob's walk. A few days later, a family friend took the boy to a playground, where he fell -- it seemed minor, but afterward, he refused to walk or even crawl. Alarmed, Powell brought him to the emergency room.

An X-ray of the toddler's leg showed rickets, a bone disease more often associated with the 19th century than the 21st.

Surprisingly, rickets is increasingly common but almost always in children of color. The bone disease is a fascinating example of how a racial health disparity evolved, even though no one had bad intentions.

When making health policy, it's tempting to presume people are equal not only in spirit but in the flesh. But for years, researchers have known that African-American patients on average fare worse with heart disease and cancer. Traditionally these differences have been chalked up to economic or social inequalities; however, some research suggests that biological differences also contribute.

Rickets also shows how such differences unexpectedly can result in discrimination.

The human skeleton operates somewhat like the body's calcium bank. When calcium is plentiful from a child's diet, the mineral gets deposited into bones and they grow. However, when calcium (which is important for many reasons, such as regulating the heartbeat) is low, the kidneys release hormones to make ''withdrawals" from the bones.

Thus if a child lacks calcium, the body begins digesting its own bones. The legs bow, the wrists swell, and hard knots appear over the ribs. In retrospect, like many kids with rickets, Powell's son wasn't growing well.

The problem, isn't only a lack of enough calcium in the diet but also a lack of vitamin D, which helps the stomach absorb calcium from food. Without vitamin D, calcium passes right out of the body.

Normally, babies build up vitamin D stores while in the uterus and after birth make their own using sunlight, since skin makes the vitamin when exposed to ultraviolet light.

But children like Jacob are at a triple disadvantage.

First, 40 percent of dark-skinned mothers in colder climates like New England are deficient in vitamin D (a risk tenfold higher than in whites), so their babies may be lacking from the get-go. People with dark skin are less able to use sunlight to make vitamin D than people with light skin.

Second, due to their skin pigments, children of color often can't compensate for a deficiency especially if they spend a lot of time indoors or wear sunscreen outdoors. Finally, when exclusively breastfed like Jacob, infants also lack an external source of vitamin D, since breast milk contains almost none, even when the mother is well-nourished.

Though there is no systematic effort to count rickets cases in the United States, numerous studies describe a resurgence in dark-pigmented children. At my hospital, doctors see perhaps a dozen new cases yearly, almost all in African-American or Caribbean children. Among numerous anecdotal reports in recent medical journals, the Archives of Diseases in Childhood last year published an article provocatively titled, ''Is nutritional rickets returning?"

More worrisome, no one knows how many infants have low vitamin D levels -- not low enough to cause rickets, but low enough to cause mild bone problems and slow their growth.

During World War I, health authorities learned from food rationing that inadequate vitamin D resulted in rickets. European children were fed cod and halibut liver oils, which are rich sources of vitamin D, and rickets cases plummeted. Soon afterward, public health authorities added the nutrient to milk, which most children drank.

Why, then, do rickets still occur? The answer is that public health policies underestimated biological differences among races.

First, fortifying milk with vitamin D to prevent rickets overlooks the problem of lactose intolerance, which results in bloating, gas, and diarrhea in response to milk. This affects as many as three-quarters of African-Americans and may cause them to consume far less milk (and vitamin D) than whites.

Second, the recommendation for many infants to use sunscreen, as suggested by the American Academy of Pediatrics in 1999, fails to distinguish between dark- and light-skinned infants, even though there is no data on whether dark-skinned infants require sunscreen to protect against skin cancer. This may also contribute to vitamin D deficiency.

Third, though almost all cases of rickets occur in children who were exclusively breastfed for more than 6 months, a 2004 Pediatrics study found that fewer than 1 in 2 doctors recommend daily vitamin D for all breastfed infants. The pediatrics academy tells pediatricians the drops are needed, but Jacob's mother, for example, says she never heard about them.

Some health-care providers may be poorly informed. However, others worry that telling women about the need for vitamin D supplementation will discourage them from nursing.

These days Powell says, ''I just want others to learn from my experience." Though many lessons can be drawn from her son's case, the most useful is the simplest: Greater awareness of universal vitamin D supplementation in breastfed infants especially children of color might eliminate childhood rickets.

Rickets reminds us that even well-intentioned public health policies can overlook biological variation among races and ultimately worsen disparities.

Dr. Darshak Sanghavi can be reached at  

(Correction: The hormone that activates the withdrawal of calcium from the bones comes from the parathyroid glands. Calcium is absorbed from food in the small intestine.)

Copyright 2005 The New York Times Company