Enigma of sun and bone
A 1-year-old was brought to a Long Island, N.Y., hospital emergency room recently, suffering from seizures. The girl's parents were also concerned that she had not yet begun to crawl. The doctor noticed that her wrists appeared widened, her ankles enlarged, and her legs slightly bowed. Because it was the fourth case he had seen in recent months, he quickly made the diagnosis: The girl had rickets.
Rickets? Isn't that a disease from an earlier era? In fact, yes, it was nearly eradicated in the 1930s, but in the past decade it's been making a comeback--especially among African-American kids. Rickets is a serious disease, caused by a deficiency in vitamin D, in which children's bones soften and break. Vitamin D regulates the body's ability to use calcium, which is required for building bone and without which the skeleton basically collapses.
Scientists see this as a disturbing nutritional trend. Indeed, Michael Holick, professor of medicine at Boston University, calls it "a severe unrecognized epidemic of vitamin D deficiency" that may be linked to a variety of chronic illnesses. He adds: "The public-health consequences of ignoring this epidemic are profound."
Sunlight is the main source of vitamin D for humans. A mere five to 15 minutes in the summer sunlight two or three times a week can provide all the vitamin D the body needs. But blood levels of vitamin D drop in winter, when exposure to sunlight decreases. The only alternative sources are vitamin D-fortified milk, orange juice, and wheat products, and oily fish such as salmon. So during the darker, winter months, the body needs help--usually in the form of a vitamin pill. The emerging debate is over how big that pill should be.
The latest statistics indicate that vitamin D levels in the population are surprisingly low. And African-Americans are disproportionately hit because dark skin diminishes production of vitamin D. According to the National Health and Nutrition Examination Survey, during the winter fully half of African-American women have insufficient vitamin D for good bones, compared with 11 percent of white women.
Daily dose. The current recommended dietary intake, or RDA, is 200 IUs for infants and adults under age 50. This was set by the Institute of Medicine's Food and Nutrition Board in 1997. Aging reduces the skin's ability to convert sunlight into vitamin D, so the RDA is 400 IUs for ages 51 to 70 and 600 IUs for ages 70 and above. But these dosages are geared only to preventing rickets. Minimum dosages for other disorders--most notably osteoporosis--have not been set.
Many vitamin D experts think these RDAs are way too low. In fact, most recommend an ideal dose of about 1,000 IUs, or 2 1/2 to five times the current RDA. "The RDAs for vitamin D are totally inadequate," Holick says. Even so, most people don't meet even those: Vitamin D levels in women older than 12 and men over 50 are below even the lowest RDA.
And bone problems may be just the tip of the iceberg. Higher levels of vitamin D might also be helpful in avoiding breast, colon, and prostate cancers. Indeed, William Grant, a senior scientist at NASA, estimates that more vitamin D could reduce the risk of 13 different cancers, resulting in 30,000 fewer cancer deaths at a savings of about $47 billion a year in healthcare costs. And that's on top of all those soft, bent, and broken bones.
This story appears in the October 27, 2003 print edition of U.S. News & World Report.