May 1, 2008 -- The reaction of an infant's immature immune system to a protein found in cow's milk infant formula may explain the suspected link between early consumption of cow's milk and an increased risk of developing type 1 diabetes later, according to a new study.
But experts who reviewed the study for WebMD say the research is mixed on the suspected link and the new report does not offer conclusive proof of cause and effect. While these experts strongly support breastfeeding, they say those mothers who can't or choose not to breastfeed shouldn't be alarmed by the report.
The Formula-Diabetes Theory
The protein under study, called beta-lactoglobulin, is found in cow's milk but not human breast milk. It is similar in structure to the human protein glycodelin, writes Marcia F. Goldfarb, author of the new report.
The report is published in the letters section of the Journal of Proteome Research. Goldfarb directs Anatek-EP, a contract protein research laboratory in Portland, Maine.
An infant's immature immune system may destroy the glycodelin in an effort to destroy the look-alike "foreign" protein beta-lactoglobulin, Goldfarb says.
Glycodelin controls the production of the body's T-cells, which help protect against infection. If glycodelin is destroyed, there could be an overproduction of T cells, she says.
The Cow's Milk-Diabetes Link Study
In the report, Goldfarb notes the conflicting results of studies looking at early introduction of formula (before four months) and diabetes.
In the adults, she found two had antibodies to beta-lactoglobulin.
In the children, all five had antibodies to beta-lactoglobulin.
While other researchers have noted that beta-lactoglobulin may generate antibodies to glycodelin, Goldfarb proposes the next step: that the immature immune system sees the beta-lactoglobulin as foreign, produces the antibody which cross-reacts with the glycodelin, and triggers the diabetes.
A Food Scientist's Opinion: Cow's Milk and Diabetes
A pediatrician and food scientist who reviewed the report took some issue with the findings and caution what is found is an association, not cause and effect.
"She is making some jumps in her logic," says Mary Ellen Camire, PhD, professor of food science and human nutrition at the University of Maine, Orono.
"She hasn't proven that the beta-lactoglobulin generates antibodies to the glycodelin -- and that's what causes the type 1 diabetes," Camire says. While the theory is plausible, "she hasn't provided the experimental research to document it," Camire says. "A lot of people receive infant formula and do not develop diabetes."
A Pediatrician's Opinion: Cow's Milk and Diabetes
The research showing an association between cow's milk and diabetes has been very mixed, adds Jennifer Shu, MD, an Atlanta pediatrician and co-author of the book Food Fights, an American Academy of Pediatrics' guide.
''It is interesting to know and may be useful," she says of the new report. "However, there have been many studies, as even they mention, that refute their findings."
If anything, she says, the research provides "another strong message to support breastfeeding."
But while breastfeeding is strongly recommended, "for people who can't or choose not to breastfeed, the only safe alternative is infant formula," Shu says.
In a policy statement, the American Academy of Pediatrics recommends breastfeeding, noting among other possible benefits a reduction in the incidence of diabetes.
Mary Martin Nordness, RD, an ambassador for the National Dairy Council, says the council supports the American Academy of Pediatrics' recommendation to breastfeed.
"If moms can breastfeed as long as they can, that is the very best," she says, with introduction of cow's milk after age 1.