By Julie Steenhuysen

A diet rich in fish and other sources of omega-3 fatty acids helped cut the risk that children with a family history of diabetes would develop the disease, U.S. researchers said on Tuesday.

"It is a relatively large effect," said Jill Norris, whose study appears in the Journal of the American Medical Association.

"It is exciting because it suggests we might be able to develop nutritional interventions to prevent diabetes."

Type 1 diabetes, formerly called juvenile diabetes, is the most common form of diabetes in children. It occurs when the immune system goes haywire and starts attacking insulin-producing cells in the pancreas.

No one knows exactly what triggers this process, but heredity and environmental factors such as diet are thought to play a role.

Several studies in animals have suggested that omega-3 fatty acids -- which are found in fish, flaxseed oil, walnuts, soybeans and other foods -- may help.

To test whether omega-3 fatty acids offer a potential protective effect, Norris and colleagues at the University of Colorado at Denver studied 1,770 children between 1994 and 2006 who were deemed at high risk for diabetes because of genetic tests or because they had a sibling or parent with type 1 diabetes.

Data about their dietary intake were collected in food frequency surveys.

Their blood was tested at least once a year for what is known as islet autoimmunity -- the development of antibodies made by the immune system that attack insulin-producing cells in the pancreas. These antibodies are considered a strong predictor of type 1 diabetes.

Fifty-eight children in the study developed these antibodies.

Overall, the researchers found at-risk children who ate a lot of foods rich in omega-3 were 55 percent less likely to have pancreatic islet autoimmunity.

"This is the first study to show this," Norris said in a telephone interview. "This is all omega-3 fatty acids, not just the kind that are found in fish."

To make sure parents in the study were accurately reporting the children's food intake, Norris and colleagues tested for the presence of omega-3 fatty acids in blood cell membranes of 244 of the children.

In that group, children with omega-3 fatty acids in their blood cell membranes had a 37 percent decreased risk of having islet autoimmunity.

"It is certainly not time to make any recommendations until we can see this in other populations," Norris said, but added that it is a very promising result.

Omega-3 fatty acids interfere with enzymes that play a role in inflammation, a potential trigger for type 1 diabetes.

At least 194 million people in the world have diabetes, and the World Health Organization expects that number to rise to more than 300 million by 2025. Most of these people have type 2 diabetes, which is linked with poor diet and lack of exercise.