The theory is that babies who can't breastfeed can drink formula fortified with prebiotics, which are food particles that promote the growth of healthy gut bacteria or flora, and build immunity against some allergens."When you change the gut flora your immunity changes as well," said Dr. John Sinn, the review's senior author from The University of Sydney's Royal North Shore Hospital in Australia.
The analysis, published on Thursday by the Cochrane Collaboration, an international organization that evaluates medical research, is an update to a previous review from 2007 that did not find enough evidence to say whether putting prebiotics in baby formula had any benefits.
Previous research had found that about 8 percent of children will develop a food allergy, 20 percent will develop eczema and up to about 34 percent will develop wheezing or asthma.
For the new analysis, the researchers were able to include four studies that randomly assigned a total of 1,428 babies to either regular formula or formula fortified with prebiotics.
The studies reported whether or not the children developed allergic reactions, such as asthma, eczema or hives between four months and two years of age.
Overall, the prebiotic formula did not prevent babies from developing asthma or hives compared to babies fed regular formula, but there was evidence to suggest it may protect against eczema.
Specifically, about 8 percent of 634 babies fed formula with prebiotics developed eczema, compared to about 12 percent of 586 babies fed regular formula.
According to the authors, 25 babies would need to be fed formula with prebiotics to prevent one from developing eczema.
However, the researchers warn that the evidence behind this finding is weak, because it's only based on four studies that were different from each other. Also, they cannot say whether any benefit from prebiotics would last beyond infancy.
Dr. Frank Greer, a professor of pediatrics at Meriter Hospital's Wisconsin Perinatal Center in Madison, said he was not "very impressed" with the evidence.
Greer, who co-authored the American Academy of Pediatrics' (AAP) clinical report on probiotics and prebiotics, said the only strategy they found to possibly prevent eczema was four months of exclusive breastfeeding.
"My basic recommendation for parents is if your child is at risk for allergies the best thing you can do is exclusively breastfeed for four months. And if you have to supplement, supplement with hydrolyzed formula," said Greer, who was not involved with the new analysis.
He said hydrolyzed formulas don't carry the same risk of allergic reactions as formulas that use cow's milk. And while he said prebiotics don't hurt, he can't say that they offer any real protection.
The AAP currently recommends women breastfeed their newborns exclusively for about the first six months of life, after which some foods can be added along with continued breastfeeding.
