Last Updated: 2003-03-31 16:13:07 -0400 (Reuters Health)

By Alison McCook

NEW YORK (Reuters Health) - Women with diabetes also appear to receive the heart-healthy benefits of a diet rich in fish, researchers said Monday.

Among women with diabetes -- a condition that places them at especially high risk of cardiovascular disease -- the more fish they ate, the less likely they were to develop heart disease over a 16 year period.

The biggest reduction in risk was seen in women who ate fish at least five times per week, who were 64 percent less likely to develop heart disease than women who seldom ate fish.

Currently, the American Heart Association recommends that adults eat at least two servings of fish each week.

Study author Dr. Frank B. Hu told Reuters Health that he suspected male diabetics would benefit from fish as well.

"For both diabetics and nondiabetics, at least two servings of fish per week is a reasonable recommendation," Hu said.

As further support for this recommendation, a growing body of research has shown that fish -- especially fatty fish such as tuna, salmon and sardines -- that contain omega-3 fatty acids have protective effects on the cardiovascular system.

Researchers have found that these substances can lower the risk of developing an irregular heart rhythm and blood clots, and can reduce levels of fat in the blood known as triglycerides -- all risk factors for heart disease.

In addition, other research has demonstrated that people who consume omega-3 fatty acids may experience a reduction in arterial hardness and blood pressure.

All of the 5,103 women included in the current study had type 2 diabetes, a form of the condition linked to obesity.

The women were participants in the Nurses' Health Study, in which they completed questionnaires every two years describing their eating habits and lifestyles.

During the current study, Hu, based at Harvard University in Boston, Massachusetts, and his colleagues reviewed dietary information submitted between 1980 and 1996, and looked at which women with type 2 diabetes developed heart disease.

Relative to women who said they ate fish less than once per month, women who reported eating fish between one and three times per month were 30 percent less likely to develop heart disease. The risk of heart disease dropped by 36 percent among women who reported eating fish between two and four times per week, relative to less frequent fish-eaters.

The relationship between eating fish and heart disease risk remained even after removing the influence of other risk factors for heart disease, the authors note in Circulation: Journal of the American Heart Association.

"Women who ate more fish were in general eating a more healthy diet and were more active," Hu explained. "However, the results did not change even after taking into account these factors."

The lowest risk of heart disease appeared in women who said they ate fish at least five times each week, who were also less likely to die from any cause during the study period, relative to women who rarely ate fish.

In an accompanying editorial, Dr. Scott M. Grundy of the University of Texas Southwestern Medical Center at Dallas writes that although many studies have suggested that omega-3 fatty acids improve heart health, more research is needed.

Studies are needed to determine if omega-3 fatty acids, which are found in over-the-counter fish oil supplements, are beneficial to patients immediately after a heart attack, he said. If they are, a longer trial could be conducted to see if they can actually prevent heart disease in the first place.

Before omega-3 fatty acids are ever considered part of standard therapy for heart disease, researchers need to ensure the quality of current over-the-counter supplements, Grundy writes, which are not controlled by the US Food and Drug Administration.

SOURCE: Circulation: Journal of the American Heart Association 2003;107.