Hydrolyzed formula contains proteins that have been broken down, or hydrolyzed, into smaller fragments. These specialized formulas, based on the milk proteins whey or casein, have been viewed as one way to ensure that babies at high risk for allergies get good nutrition without adding to their risk. Formulas can be partially or extensively hydrolyzed.
As we noted in our book, the science underlying this idea is not on very solid ground, and the results of an analysis of 37 studies of outcomes with hydrolyzed formula don’t improve that stability. This meta-analysis–in which the researchers data crunched the findings from the 37 different studies in one big batch–included more than 19,000 participants. First author Robert Boyle and colleagues found “no consistent evidence” that formulas with proteins partially or extensively broken down reduced risk for allergies or autoimmune disease in high-risk infants.
For the babies whose diet included the specialized formula, odds for eczema fell by about 16% for partially hydrolyzed formula and by 45% for extensively hydrolyzed casein-based formula, but increased by 12% with whey-based, extensively hydrolyzed formula. In addition to these mixed findings, the authors report that conflict of interest and publication bias were evident for some outcomes, like wheezing and eczema. They point out that they did not include some studies that are under a cloud of suspicion following accusations of fraud.
The US Food and Drug Administration has approved a health claim that these hydrolyzed formulas might reduce risk for infants, but Boyle and co-authors disagree, saying that their results don’t support recommendations for hydrolyzed formula for infants at high risk for allergies.