Including fish regularly in their diet helped reduce the risk of heart disease for women with type 2 diabetes.
That research is consistent with other studies that show the omega-3 fatty acids found in fish reduce the risk of heart disease in healthy people.
“There are a lot of clinical trials looking at the effect of omega-3 fatty acids on blood lipids,” says Frank B. Hu, M.D., the lead author of the study and an associate professor of nutrition and epidemiology at the Harvard School of Public Health. Hu added that two completed trials, conducted in people with heart disease, found that the consumption of fish or fish oil significantly reduced mortality.
Hu and his research team studied the data in the ongoing Nurse’s Health Study, which began in 1976 and asked 121,700 female nurses about their lifestyle, nutrition and health habits as well as their medical history.
They focused on more than 5,000 nurses who were diagnosed with type 2 diabetes between 1976 and 1994 but did not have a history of heart attack, stroke or cancer. The women were divided into categories as to how much fish they typically ate.
Those who ate fish one to three times a month reduced their risk of heart attack by 30 percent, while those who ate fish once a week reduced it by 40 percent. But women who ate fish five or more times a week reduced their risk of heart disease by 64 percent. Those who ate more fish also ate more fruits and vegetables and less red and processed meats.
But is it something protective in the fish itself, or is the fact that someone with a plate of salmon isn’t eating a steak?
“There are some biological substances or compounds in fish – the omega-3 fatty acids – that are beneficial,” says Hu. “Whether it’s the substitution for other foods such as steak couldn’t be answered definitively because we didn’t assign people to fish or non-fish groups. But we did take into account the differences of red meat and other foods, and the protective effects of fish are still there.”
This study put to rest fears that a diet high in fish might actually worsen control of glucose, and it showed that women with diabetes could gain the same protective benefits as healthy people from a diet containing fish.
Does the fish actually reduce the risk of diabetes or help the body to process insulin more effectively?
“That we haven’t looked at, but it’s possible,” Hu says. “There is some evidence, but the data is not convincing.”
But for those with diabetes, the omega-3 fatty acids found in fish help protect against heart disease by decreasing blood triglyceride levels, improving the functioning of blood vessels and reducing the risk of blood clots.
Fish that are high in omega-3 fatty acids include mackerel, lake trout, herring, sardines, tuna and salmon. The American Heart Association recommends that adults, except for pregnant women, should eat two servings of fish each week.