The American Academy of Pediatrics (AAP) released new guidelines on vitamin D for infants, children and adolescents today at a time when medical conditions attributable to low vitamin D levels such as rickets appear to be on the rise in the U.S.
Rickets first became a problem in the U.S. during the 18th century, in part because smoke from factories shielded people from the sun's rays -- an important source of vitamin D. Rates of the disease, which weakens bones, were brought down through improved nutrition.
"There's been increased case reports and people describing it over the past five to 10 years; whether this is a true increase is unclear," said Dr. Steven Abrams, a pediatrician at the Baylor College of Medicine who has been on previous AAP vitamin D guideline committees.
Because the Centers for Disease Control and Prevention does not have exact numbers on rickets cases, recent concerns about its return are difficult to quantify.
The new pediatric guidelines recommend a daily dose of 400 international units of vitamin D per child per day -- doubling the group's old recommendations.
"The recommendation is going to be essentially a supplement for every child and adolescent in the United States," said Dr. Frank R. Greer, a pediatrician at the University of Wisconsin and one of the authors of the guidelines.
Greer notes that while children could get an adequate amount of the nutrient from drinking six glasses of milk a day or eating fatty fish such as salmon and mackerel, children are unlikely to do either of those.
But he also stresses that parents should not over-supplement their children.
"What we don't want is for parents to give their children more than 400 units a day," he said.
One problem with maintaining adequate vitamin D levels in children, and even in adults, has been that other wellness guidelines have gotten in the way.
Sun exposure, while necessary for vitamin D, is discouraged because of the risks of skin cancer. And mothers are encouraged to breastfeed their infants -- but with more than half of American women potentially vitamin D deficient, and with breast milk not a good source of the vitamin in general, many babies will not get adequate amounts from their diets.
The use of infant formula avoids that problem, because it is fortified with an adequate amount of vitamin D.
"Breastfeeding babies are at particular risk because there's not much vitamin D in human milk," said Greer.
"The rickets that's been seen in the United States has been largely in minority populations who've been part of the WIC [Women, Infants, Children] program, where they've been emphasizing breastfeeding," said Greer, noting that 55 percent of all infants in the U.S. are involved in the program to provide food, health care and nutrition information for low-income women.
And while breast milk may not be a good source of vitamin D in any case, underprivileged, minority populations are more likely to be deficient in the vitamin.
"Any kids whose mothers are vitamin D deficient ... are at risk for getting full-blown rickets," said Greer. "[The presence of rickets] usually becomes obvious when the child begins to walk."