Kids Come Up Short
Children found lacking in vitamin D, other nutrients
Parents of children who happily eat what's put in front of them might assume their kids are well nourished. But two new studies drive home the importance of varying that diet. Deficiencies of vitamin D, omega-3 fats, and other healthful compounds are common, it turns out—and consequential.
Growing evidence links vitamin D deficiency not only to weak bones but also to impaired immunity, asthma, and diabetes, among other problems. And some of the latest research, published this month in the journal Chest, finds that rates of asthma and related respiratory problems climb in kids who are short on other commonly missing essentials, including vitamins C and E and omega-3 fatty acids. A team at the Harvard School of Public Health evaluated the diet and respiratory health of some 2,000 North American high school seniors and found that teens who skimped on fruit, vegetables, and other healthful foods were most likely to have problems such as coughing, wheezing, episodes of bronchitis, and asthma.
Vitamins C and E, which are abundant in fruit and dark-green vegetables, may "protect the lung from stress," says Harvard research fellow and study leader Jane Burns. Omega-3 reduces inflammation, a key feature of asthma, in which airways swell and make breathing difficult. Oily fish like salmon, mackerel, and tuna—as well as cod-liver oil—are rich in both omega-3 and vitamin D.
D minus. Vitamin D can also be obtained from fortified milk and sunshine—and many kids should be getting more of both. In another new study, reported in the July issue of the American Journal of Clinical Nutrition, researchers found that 55 percent of outwardly healthy children and teenagers they tested didn't have enough vitamin D to grow healthy bones. Dark-skinned children were particularly likely to be short of the bone-building vitamin, according to Babette Zemel, an author of the study and director of the Nutrition and Growth Laboratory at Children's Hospital of Philadelphia. The reason: The melanin that makes their skin dark also blocks ultraviolet rays, which the body uses to make vitamin D. In winter, when the sun was weakest, more than 90 percent of blacks in the study were vitamin D deficient.
The older teenagers tended to have reduced levels of vitamin D even when they drank plenty of milk. That may be because they play outside less than younger kids do, Zemel says. Her advice: Point kids outside, and wait a few minutes before putting on sunblock; 10 minutes of midday summer sun provides 10,000 international units of the vitamin—more than enough for a day. (Like melanin, sunblock prevents the skin from making vitamin D, so a bit of lotion-free exposure is necessary to grab the benefit.)
The American Academy of Pediatrics recommends that children get their vitamins from food, not pills. But recognizing that kids are often short on D, some so short that they develop the bone-bending disease rickets, the academy recommended in 2003 that infants and children take in at least 200 IUs of vitamin D daily, the equivalent of two 8-ounce glasses of milk. Breastfeeding infants often need supplements, because breast milk doesn't contain enough of the healthy-bone vitamin.
This story appears in the July 23, 2007 print edition of U.S. News & World Report.