Making sure fish ends up on your dinner plate a couple of times a week may be a good way to cut your risk for developing heart disease, but it may not do the same for diabetes, new study findings hint.

In the study, researchers found no evidence of reduced risk for diabetes among adults who ate more fish, or the essential omega-3 fatty acids obtained primarily from seafood.

Rather, their findings suggest that eating 2 or more servings of fish a week may slightly increase diabetes risk.

Diet is a key factor in preventing the onset of diabetes in adults, but how omega-3 fatty acid intake impacts diabetes risk is still unresolved, Dr. Frank B. Hu, at Harvard School of Public Health in Boston, Massachusetts, and colleagues explain in the American Journal of Clinical Nutrition.

They examined ties between fish and omega-3 fatty acid intake and the development of diabetes among 152,700 women enrolled in the Nurses’ Health Study and 42,504 men enrolled in the Health Professionals Follow-Up Study.

Overall, 9,380 cases of adult-onset diabetes developed among these healthcare workers during up to 18 years of follow up.

After adjusting for lifestyle and other dietary factors, plus body weight, family history of diabetes, and menopausal status and hormone use when applicable, Hu’s team noted increased diabetes risk “in all cohorts” consuming higher levels of omega-3 fatty acids.

Diabetes was 1.17 times more likely among people who ate fish 2 to 4 times a week, and 1.22 times more likely among those who ate fish 5 or more times a week, relative to those who ate lesser amounts of fish.

Dr. Hu and colleagues emphasize that numerous studies have demonstrated beneficial effects of fish and omega-3 fatty acids on multiple risk factors associated with diabetes, and on heart disease - the major sequelae of diabetes.

They say further study is needed to figure out the “clinical relevance” of the current findings and determine the mechanisms behind their observation that high fish intake may raise diabetes risk.

SOURCE: American Journal of Clinical Nutrition, September 2009