March 31, 2003 -- Eating fish regularly is believed to reduce the risk heart disease events like heart attack and stroke in healthy people. Now new research suggests it may be particularly protective against heart disease in women with diabetes.
Women with type 2 diabetes who ate fish once a week were 40% less likely to develop heart disease than those who rarely ate it, and eating fish almost every day was associated with a two-thirds reduction in risk. The women who ate more fish also tended to eat less red meat and more fruits and vegetables, but this and other studies point to a direct protective benefit for eating seafood, says researcher Frank B. Hu, MD, of the Harvard School of Public Health.
"This provides strong evidence that fish consumption is beneficial," says Hu, who is one of the nation's leading investigators of nutrition and disease risk. "Eating fish should be strongly recommended for people with diabetes."
The American Heart Association (AHA) currently recommends that adults, with the exception of pregnant women, eat at least two servings of fish each week. It is believed that omega-3 fatty acids abundant in the fat of many fish reduces the risk of heart disease by lowering triglyceride levels, improving blood vessel function, and reducing blood-clot formation.
But AHA spokeswoman Alice H. Lichtenstein, DSC, says even though studies like this one are impressive, they do not prove that eating fish alone will ward off heart disease. That is because most are observational, meaning they rely on participant recall. Lichtenstein is a professor of nutrition at Tufts University.
"People who eat a lot of fish also tend to lead healthier lifestyles in general," Lichtenstein tells WebMD. "Even though these studies try to control for lifestyle factors, it is very difficult to do this. So we can't really say how protective fish consumption is."
The latest research, to be published April 15 in the AHA journal Circulation, included some 5,100 women with type 2 diabetes taking part in the ongoing Nurses' Health Study. Having diabetes is one of the leading risk factors for heart disease.
The women were divided into five categories according to how often they ate fish, with the lowest consumers eating fish less than once a month and the highest eating it five times a week or more. Compared with those who seldom ate fish, eating seafood one to three times a month was associated with a 30% reduction in risk. A risk reduction of 40% was seen in those eating fish once a week, and those who ate fish two to four times a week had a 36% reduction in risk. The biggest risk reduction --64% -- was seen in women who ate fish five times a week or more.
In this study, the more fish the women ate the more protected they were. But a similar Harvard study reported late last year found that eating as little as one serving of fish a month was as protective against strokes in men as eating it almost every day. That study also found all fish to be protective, and not just those high in omega-3 fatty acids, such as salmon, tuna, mackerel, sardines, and trout.
Lichtenstein says the many unanswered questions make it difficult to make recommendations about eating fish and heart health. While most people would probably be better off adding more fish to their diets, Lichtenstein says other lifestyle changes are probably more important for people at risk for heart disease. The top three, she says, are maintaining a healthy body weight, not smoking, and exercising regularly.
"Even if it is true that omega-3 is protective it doesn't mean that dribbling fish oil over a hot fudge sundae makes it good for you," she says. "We know that maintaining a healthy lifestyle is important, but that message often gets lost. If the only thing someone does to lower their risk is eating more fish, I'm not sure that they will be much better off."