The study, published in The British Medical Journal, reviewed data on hydrolyzed baby formula, which is treated with heat to break down milk proteins.
It has been previously stated that giving this formula to children at risk of conditions such as milk allergy and eczema, instead of standard formula, can reduce the chance of infants developing the conditions.
Previous claims disproved
The US Food and Drug Administration (FDA) has previously approved a manufacturer’s claim that a partially hydrolyzed formula may reduce risk of eczema in some infants, and a Cochrane review in 2006 found limited evidence that feeding an infant hydrolyzed formula may reduce risk of milk allergy in babies and children.
However, this new research showed there was no statistically significant reduction in risk of these conditions amongst babies using hydrolyzed formula.
The paper also mentions connections between some studies and formula manufacturers.
Study for new UK guidelines
Dr Robert Boyle, senior author of the study from the Department of Medicine at Imperial College London, told DairyReporter that the paper is part of a bigger study his group is doing, which is funded by the UK Food Standards Agency (FSA).
The group’s overall study includes anything related to immune health and the diet of the mother or the infant, in the first year of life, said Boyle. They looked at other factors, including probiotics, vitamins, and minerals.
These other studies will form the basis of potential future papers, and the report that is being given to the government. Boyle anticipates their first draft will be finished in April.
“It's part of a bigger project which is still going, it's taken us several years, looking at all dietary exposures in early life and how they influence immune health,” Boyle told DR.
Other groups are also contributing to the government study, for example on obesity, as the FSA looks to revise its infant feeding guidelines this year.
Global studies on formula analyzed
In the hydrolyzed baby formula paper, the team analyzed 37 different studies around the world that included over 19,000 participants. This new study is the most complete and robust assessment of all the evidence to date, says Boyle.
“We didn't do our own trial, we synthesized the results of all the trials that have been done, and pulled the data out and used various methods to look at the quality of the studies done, and then pooled the data from the different trials, it’s called meta analysis; it's much more powerful than doing individual trials,” Boyle said.
Interest from Australia
Boyle said that there has already been interest in this portion of the study.
“This is the first paper from the project. There has been some interest in the results of this particular study, the Australians are just rewriting their allergy prevention guidelines, they were very interested to know the results of our review,” Boyle told DR.
Looking at the results
The study found there was no significant reduction in the risk of developing eczema, wheezing, or food allergy (including cow’s milk allergy) from using the hydrolyzed formulas. Some of the trials also investigated the risk of developing type 1 diabetes, but no link was found.
"Despite parents being advised these hydrolyzed milk formulas may reduce the risk of conditions such as milk allergy and eczema, we found no evidence to support these claims," Boyle said.
"Not only did we find no evidence of reduced risk from hydrolyzed formula, but we found very few studies which were methodologically sound and without a conflict of interest. For instance, in some of the studies all babies were started on the formula at birth, or a few days after. This raises questions about whether enough was done to promote breastfeeding to the mothers in those studies.”
In spite of any potential conflicts of interest, Boyle said the data was analyzed from all studies.
He added that the better the quality of the study, the less effect there was of the hydrolyzed baby formula seen in the results.
Statistician points to publication bias
Professor Jo Leonardi-Bee, senior statistician on the study from the Division of Epidemiology and Public Health at the University of Nottingham, added that the results may not be representative of all studies conducted in this area.
"Our research suggests that there was evidence of publication bias, where some studies that showed formula milk didn't actually reduce allergies may not have been published," Leonardi-Bee said.
She says further studies into infant milk formula must be more robust.
“We need to ensure future studies are carefully designed, so that our guidance to parents is based on reliable evidence.”
Comparisons of feeding
The trials analyzed by the team mostly investigated whether hydrolyzed milk formula could reduce the risk of allergies or eczema in children considered at a high risk of the conditions. This usually meant the youngster had a first-hand relative, such as a sibling or parent, with allergies or eczema.
The trials compared hydrolyzed formula to standard formula, and some trials made comparisons with breast milk or between two different hydrolyzed formulas.
Current recommendations need revision
The authors of the paper suggest that current recommendations to use hydrolyzed formula in place of standard cows’ milk formula to prevent allergy in infants at high risk should be revised.
The study found no consistent evidence to support the current recommendations and found evidence of publication bias, methodological biases, and conflict of interest in those studies reporting allergic outcomes.
The authors conclude that any future trials on hydrolyzed formula should be prospectively registered, independently funded, and include adequate oversight to ensure that they do not negatively impact on breastfeeding in study participants.