An astonishing forty percent of healthy babies and toddlers in a recent study had low levels of vitamin D. Results of this important study appear in the June 2008 Archives of Pediatrics and Adolescent Medicine. Children can get vitamin D in the diet, but the skin can also make vitamin D in response to time in the sun. Optimal levels of vitamin D are important not only for bone health, but also for helping to prevent cancer, infections, and other important diseases. Severe vitamin D deficiency can cause rickets, a bone condition that has been increasing around the world (even in sunny California, Nevada, Texas, and North Carolina, among other US states).
What predicts low levels of vitamin D? The child’s gender? Their nutrition? The amount of time spent in the sun? The season of the year? Sunscreen use? The darkness of the skin? Parents’ health habits? The current study looked at healthy children up to age two who went to Children’s Hospital Boston for a routine health visit over the course of a year and a half. Vitamin D levels were measured by blood tests. The 40 percent found to have low levels is similar to what a previous study found in US teens (42 percent not getting enough). About 12 percent of the healthy babies and toddlers in this study had levels low enough to be called vitamin D deficient. Their bones were checked by x-ray, and about a third of them already had decreased bone density. And 7.5 percent of them already had the bone changes of rickets.
Overall, the season of the year didn’t correlate with the children’s odds of vitamin D deficiency (although, unexpectedly, average vitamin D levels in the babies were higher in the winter!). There was no affect on vitamin D levels found based on the amount of time spent outdoors, skin color, sun sensitivity, or sunscreen use – considered individually or together. Nor was there any difference based on gender. Breastfed babies, though, who weren’t getting vitamin D drops, were 10 times more likely to be deficient.
Among toddlers, vitamin D levels closely mirrored how much milk they drank. Eating fortified cereal had no impact on vitamin D levels. In toddlers, vitamin D did vary a bit with body weight. Obese toddlers were somewhat more likely to have lower vitamin D levels.
Bottom line: I support the American Academy of Pediatrics recommendation that breastfed babies all start taking at least 200 IU of vitamin D within the first two months of life. I think 400 IU may even prove to be better. It’s not that breast milk is lacking; it’s that throughout most of human history babies spent a lot more time outdoors than they do today, without sunscreen, and with bodies adapted to the latitude where they lived. In this Boston study, the child who was outside the most averaged only 3 hours outdoors per day. When my parents were young, a lot of children lived on farms and were outside most of the day during the summer months Because of the changes in the earth’s ozone layer, though, it’s no longer safe to spend so much time in the sun without sunscreen, which puts the brakes on making vitamin D. Some sunshine is great for kids, but in this century it’s important to protect kids from too much sun exposure. –What about older kids? For children age one through eight who don’t drink 2 cups of vitamin D milk a day, or for those over nine years old who don’t drink 3 cups of vitamin D milk a day, I recommend ensuring another source of vitamin D.
Gordon CM, Feldman HA, Sinclair L, Williams AL, Kleinman PK, Perez-Rossello J, Cox JE. Prevalence of Vitamin D Deficiency among Healthy Infants and Toddlers. Archives of Pediatrics and Adolescent Medicine. 2008; 162:505-512.