In a discovery that could lead to a revolution in the way infants are fed, researchers have implicated exposure to a common milk protein in the first nine months of life as a major cause of insulin-dependent diabetes, which affects more than 1 million Americans.
If confirmed by further studies, the controversial findings by Canadian and Finnish researchers could bring about a sharp decrease in the incidence of diabetes. About one-quarter of the population is genetically susceptible to diabetes.
"If this is true, we should be able to prevent the disease altogether," said Dr. Hans-Michael Dosch, a pediatric immunologist at the Hospital for Sick Children in Toronto and leader of the research team.
Reaction to the study by other researchers and experts in diabetes was cautious. "It's very important, but it needs more work and more confirmation," said Dr. F. Xavier Pi-Sunyer, a diabetologist at the Columbia University College of Physicians and Surgeons and president of the American Diabetes Assn.
"It does not mean that children should stop drinking milk or that parents of diabetics should withdraw dairy products. These are rich sources of good protein."
Some diabetes researchers have long suspected a role for the milk protein because a segment of it is chemically identical to a protein on the surface of pancreas cells that produce insulin, which regulates blood sugar levels.
Antibodies produced against the milk protein during the first year of life, the researchers speculate, also attack and destroy the pancreas in a so-called autoimmune reaction, producing diabetes in people whose genetic makeup leaves them vulnerable.
Strong support for this theory is reported today in the New England Journal of Medicine. Dosch and his colleagues in Toronto and Finland studied 142 Finnish children with newly diagnosed diabetes. They found that every one had at least eight times as many antibodies against the milk protein as did healthy children, clear evidence that the children had a raging autoimmune disorder.
Although Dosch said it is "far too early" for mothers to change their feeding habits, "we do encourage breast feeding whenever possible," especially in families with a history of diabetes.
This week, the research team will begin a clinical trial in which 3,000 children will receive no dairy products during the first nine months of life. The study may take 10 years but, "we'll get a definitive answer one way or the other," Dosch said.
In the meantime, parents were advised not to rush into dietary changes for their infants. "It's a very interesting study, but the data are very preliminary," said Robert Gelardi, executive director of the Infant Formula Council in Atlanta, a group that represents manufacturers. "This is just another one in a series of factors that might have some influence on diabetes."
Physicians should absolutely not issue a warning to parents based on the study, said physiologist Mark Atkinson of the University of Florida Medical School in Gainesville. "It's a very interesting and very exciting study, but it really needs to be confirmed before we can recommend any changes in feeding infants, even in diabetic families."
The link between cows' milk and diabetes has been suspected for more than a decade. Epidemiological studies, for example, show that the incidence of diabetes is highest in regions with high milk consumption.
Finland, which has the world's highest rate of dairy product consumption, has the highest incidence of insulin-dependent diabetes. The disease strikes about 40 children out of every 1,000 there, contrasted with six to eight per 1,000 in the United States.
Other studies have shown that children who are exclusively breast fed have about one-third the normal risk of developing diabetes. In the United States, less than one out of every three mothers breast feeds after the first two months, according to La Leche League International, which promotes breast feeding. The remainder use infant formula, most of which is based on cows' milk.
Recently, Dr. Julio M. Martin, an immunologist, and his colleagues at the University of Toronto have shown that the disease can be prevented or minimized in diabetes-prone rats by keeping dairy products out of their diet. Conversely, giving them large amounts of the suspect milk protein, called bovine serum albumin, greatly increases the incidence of diabetes.
"We had to find a way to ask whether the human disease is similar to the animals," Dosch said. The way to do that was to look for antibodies against bovine serum albumin in children who had recently been diagnosed as having diabetes.
Although today's paper reports on results with only 142 diabetic children, Dosch said the team has now studied nearly 400. "We found a strong immune response in all but one of the patients, but very rarely in (healthy children and adults) and never at the same high levels.