TUESDAY, Sept. 30, 2003 (HealthDayNews) -- People who develop type 1 diabetes have a genetic predisposition to the disease that is triggered by some, as yet unknown, environmental factor.
"It's known that people have a genetic predisposition. But there's something which triggers it that is environmental, and it's still not clear what that is," says Antony Horton, scientific program manager at the Juvenile Diabetes Research Foundation in New York City.
Quite a bit of controversy among researchers has centered on whether this trigger might be the protein in cow's milk or wheat gluten, the concentrated form of the protein contained in wheat flour that's sometimes used in infant cereals.
Two studies appearing in the Oct. 1 issue of the Journal of the American Medical Association seem to point the finger at the latter. But some diabetes experts say that conclusion may be premature.
The authors of the first study did blood tests and collected detailed diet information on 1,183 American infants considered to be at risk for type 1 diabetes.
The data revealed that infants who were susceptible to diabetes -- because of a family history or genetic makeup -- and who were fed cereal before they were 4 months old or after the age of 6 months, had a higher risk of developing antibodies to the islet cells of the pancreas.
These islet cells are responsible for producing insulin, the hormone that ushers glucose into individual cells. The immune systems of people with type 1 diabetes -- formerly called juvenile onset diabetes -- mistakenly attack these islet cells so they are no longer functional. Autoantibodies to the islet cells are often present for years before the islet cells themselves are destroyed. This is called islet autoimmunity (IA).
Specifically, those children who were fed cereals both with and without gluten before 4 months of age had a four times greater risk for IA, and those who were first fed cereal at 7 months or older had a five times increased risk, the study found. Both of these groups were compared to children in the 4- to 6-month age range, which is when U.S. pediatricians generally recommend introducing solid foods, especially cereals.
The authors also found that introducing cereals while the child was still breast-feeding reduced the risk of IA. No association was found between IA and cow's milk.
The authors of the second study, based in Germany, followed 1,610 newborns of parents with type 1 diabetes to see if timing of exposure to breast milk, milk formula, solid foods or gluten-containing foods was associated with a greater risk of developing antibodies to islet cells.
This time, early introduction of gluten-containing foods was found to be a risk factor for IA. Babies who ate gluten before the age of 3 months had a fivefold higher risk for developing the autoantibodies, compared with those who ate gluten after 3 months of age.
One weakness of both studies was that they based their conclusions on the development of autoantibodies, not on the development of diabetes.
"The more autoantibodies you develop, the stronger the indication that you will likely develop diabetes. But some people can have antibodies all their lives and never develop diabetes," Horton says.
The study authors feel the research results are bringing the world closer to some much-needed answers about what causes type 1 diabetes. Others aren't so sure.
"We are closer to knowing what is causing type 1 diabetes," says Jill Norris, lead author of the first study and an associate professor of preventive medicine at the University of Colorado Health Sciences Center in Denver. "Certainly, [these studies] highlight the point that there is something in the infant diet that is important and whether it's strictly timing or some combination of timing and dose, we haven't entirely sorted [it] out."
Other experts urge caution in interpreting the study results.
The two studies, writes Mark Atkinson, a professor of pathology at the University of Florida and author of an accompanying editorial in the journal, "do not present sufficient evidence to suggest that 'infant cereal causes diabetes,' and hopefully will not be misinterpreted as such by parents and the public."
Adds Horton: "These studies are not wholly conclusive. There's a controversy in the literature which has not been ironed out and this study doesn't iron it out. This is just an interesting observation but it's still not a strong support of the actual candidate being wheat gluten."
About 17 million people in the United States have diabetes, according to the American Diabetes Association. Of those 17 million, about 5 percent to 10 percent have type 1.
In type 1 diabetes, the body's inability to produce insulin requires people to inject insulin daily to survive and to keep their levels of glucose -- blood sugar -- under control. If glucose levels get too high, it increases the risk of complications such as blindness or kidney problems.
More information
For more on type 1 diabetes, visit the Juvenile Diabetes Research Foundation or the American Diabetes Association.
