Vitamin D Levels Inadequate in 70 Percent of U.S. Children

Seventy percent of American children are at increased risk for bone and heart disease because of low levels of vitamin D, according to a recent study published in Pediatrics.

"In adults, there has been an increased interest in associations between low vitamin D levels and all sorts of cardiovascular risk factors, such as high blood pressure and diabetes, so we decided to look at this in children," said study leader Michal Melamed, M.D., assistant professor of medicine and epidemiology and population health at Albert Einstein College of Medicine of Yeshiva University, Bronx, N.Y., in an interview posted on the university's Web site.

In the study, "Prevalence and Associations of 25-Hydroxyvitamin D Deficiency in US Children: NHANES 2001–2004," researchers found that of a nationally representative sample of more than 6,000 individuals ages 1-21 years who participated in the National Health and Nutrition Examination Survey, 9 percent were vitamin D-deficient (i.e., serum 25 [OH]D level less than 15 ng/mL). If that percentage were applied nationwide, Melamed said, it would mean that more than 7 million American children and young adults are at risk for rickets.

In addition, 61 percent of children in the study were vitamin D-insufficient (i.e., serum 25 [OH]D level of 15-29 ng/mL).

Melamed said study participants with low levels of vitamin D had higher blood pressure; higher parathyroid hormone levels; lower calcium levels; and lower HDL cholesterol levels than those with adequate vitamin D intake.

The researchers found that low vitamin D levels were most common in children who were older, female, non-Hispanic black, Mexican-American or obese; those who drank milk less than once a week; and those who spent more than four hours a day watching TV, playing video games or using computers.

The American Academy of Pediatrics, or AAP, issued new guidance on the prevention of rickets and vitamin D deficiency (11-page PDF; About PDFs) in infants, children and teens last year. In its report, the AAP doubled the recommended amount of daily vitamin D intake to 400 international units, or IUs, for these populations.

Michelle May, M.D., of Phoenix, a member of the AAFP Commission on Health of the Public and Science, said the few moments it takes to discuss nutrition with children and their parents can pay huge dividends.

"Encourage children to consume vitamin D-fortified milk, yogurt, orange juice and oily fish, such as tuna," said May. "However, diet alone may not provide enough vitamin D for children who do not also get sun exposure."

The AAP's report includes specific recommendations that the following groups receive a daily supplement of 400 IU of vitamin D:

May said supplements also may be advisable for children who have limited sun exposure, including those with dark skin and those who live in northern climates, especially during the winter.

The body uses ultraviolet B, or UVB, sunlight to convert cholesterol in the skin into vitamin D, but Melamed said children spend less time outside than they once did. The widespread use of sunscreens that block UVB rays has compounded the problem, she said.

May said sun exposure is the most efficient way to get adequate amounts of vitamin D.

"Just 10 to 15 minutes of unprotected midday sun exposure in a light-skinned individual a few times a week is enough," May said. "Apply sunscreen for longer exposure."

May also said physicians should be aware of and advise patients who might be eligible about initiatives such as the U.S. Department of Agriculture's Women, Infants and Children, or WIC, program. WIC provides federal grants to states for supplemental food, health care referrals, and nutrition education for low-income pregnant and postpartum women, as well as for infants and children as old as age 5 years who are at nutritional risk.