Although studies have shown a positive benefit from fish consumption (and consequent intake of omega-3 fatty acids) on the risk of coronary heart disease (CHD) and sudden cardiac death in the general population, few studies have focused on the effect in patients with diabetes. Hu and colleagues performed a prospective cohort study to evaluate the effect of fish and long-chain omega-3 fatty acids on the incidence of CHD and total mortality among women with diabetes who participated in the Nurses' Health Study.

The study included 5,103 women who reported having physician-diagnosed type 2 diabetes on any questionnaire between 1976 and 1994. The Nurses' Health Study began in 1976 by surveying 121,700 registered nurses about their personal medical history and lifestyle via questionnaires. Follow-up questionnaires were mailed every two years for updates on potential risk factors. Patients with a history of CHD, stroke, or cancer reported on the 1980 questionnaire or earlier were excluded at baseline from the cohort study by Hu and colleagues. The dietary questions were analyzed to determine the type and quantity of fish consumption and calculate long-chain omega-3 fatty acid intake. Medical records were reviewed, interviews were conducted, and death certificates were obtained to ascertain the end points of the study: incidence of CHD and all-cause mortality between 1980 and 1996. A total of 362 cases of CHD (141 deaths from CHD and 221 nonfatal myocardial infarctions) and 468 deaths from all causes (161 from CHD or stroke, 172 from cancer, and 135 from other causes) were discovered. After adjustment for age, a trend toward significance in the association of increased fish intake and reduced incidence of CHD and reduced total mortality was noted. Further analysis demonstrated no statistically significant differences in the incidence of CHD between fish consumers with or without diabetes.

The authors conclude that regular intake of fish should be part of the dietary recommendations in women with diabetes, and that these findings also have implications for women without diabetes.

editor's note: Given the observational nature of the study, more rigorous trials are needed to define the role of omega-3 fatty acids in patients with diabetes. In the meantime, encouraging patients who have diabetes to eat more fish is reasonable based on secondary CHD prevention trials, the safety profile of fish, and the latest recommendations of the American Heart Association (AHA). The AHA recommends that patients without CHD eat a variety of fish at least twice a week. Patients with CHD should consume about 1 g of eicosapentaenoic acid (and docosahexaenoic acid) per day, preferably from oily fish. Consumption of a wide variety of fish is suggested to reduce exposure to mercury and other environmental toxins.—s.m.s.