Vitamins are powerful little molecules. Not only do they prevent scurvy and help build healthy bones; they also can skew a developing immune system to produce its many cells in different amounts than usual—which might influence a child's risk for allergies and asthma. Researchers at Children's National Medical Center in Washington, D.C., looked at a large data set to find out whether children who were given multivitamins early were more likely to get allergies.

What the researchers wanted to know: Does giving an infant vitamins change the child's risk of allergies or asthma?

What they did: The researchers used data from a national study on the health of 8,285 mothers and their children born in 1988. Ninety percent of the mothers and children in the first survey also took part in a 1991 follow-up, when the children were 3 years old.

What they found: Black infants who were given multivitamins were more likely to develop asthma, and infants fed formula and multivitamins were more likely to develop food allergies. Pediatricians often recommend multivitamins for infants who are breastfed to ward off rickets caused by vitamin D deficiency.

What the study means to you: It's possible that children should be given fewer vitamins, or vitamins formulated differently, to help reduce the risk of allergies and asthma.

Caveats: This is a survey‑it doesn't show that vitamins caused allergies or asthma. It only counted diagnoses made by the age of 3, and parents had to report their own children's diagnoses—which they could have gotten wrong. Also, the researchers write that asthma might be diagnosed more often in black children than in white children, and that intolerance to cows' milk, which is more common among blacks, might be incorrectly diagnosed as a food allergy. And the data is 13 years old, so things may have changed since then.

Find out more: The American Academy of Pediatrics recommends giving breastfed babies supplemental vitamin D.

Read the article: Milner, J.D., Stein, D.M., McCarter, R., and R.Y. Moon. "Early Infant Multivitamin Supplementation is Associated with Increased Risk for Food Allergy and Asthma." Pediatrics. July 2004, Vol. 114, No. 1, pp. 27-32.