MONDAY, Nov. 8, 2004 (HealthDayNews) -- Women who eat foods high in oils containing alpha-linolenic acid appear to have a lower risk of dying from heart disease and of sudden cardiac death than women whose diets are low in the substance.
However, such diets don't seem to have an impact on nonfatal heart attacks, according to research presented Monday at the American Heart Association's scientific sessions in New Orleans.
The findings were only "observational," meaning they don't necessarily indicate any cause-and-effect relationship, the researchers said.
"It looks like eating this type of food might be helpful, but you can't prove it or make mandates," said study author Dr. Christine M. Albert, an assistant professor of medicine at Harvard Medical School in Boston.
Alpha-linolenic acid (ALA) belongs to the family of omega-3 fatty acids. Overall, "the evidence is very compelling for omega-3 fatty acids conferring a cardioprotective effect," said Samantha Heller, senior clinical nutritionist at New York University Medical Center in New York City.
Omega-3 fatty acids are present in fish such as mackerel and salmon. ALA is found in some green leafy vegetables such as kale, broccoli and Brussels sprouts; walnuts and certain other nuts; canola oil; and some salad dressings and margarines.
"The highest source is flaxseed," Albert said.
Albert and her team examined the records of 76,763 women who were part of the Nurse's Health Study and who had completed an initial food questionnaire in 1984. The questionnaire, which documented what and how much they ate, was updated every four years.
During 16 years of follow-up, 169 women suffered sudden cardiac death, 564 died from coronary artery disease and 1,325 had heart attacks but did not die from them.
The women were categorized into five groups based on how much ALA they consumed, with the average intake ranging from 0.7 grams a day to 1.5 grams.
Women with the highest intake had a 46 percent reduced risk of dying from sudden cardiac death compared to women who had the least intake. Women in the highest group were also 21 percent less likely to die from coronary heart disease than women in the lowest group. This high level of intake corresponded to about two capsules of flaxseed oil, Albert said.
It's not clear what mechanism may be at play, but ALA did not influence nonfatal heart attacks, the study found. However, ALA may prevent life-threatening rhythmic disturbances of the heart, Albert said. "It may stabilize the chaotic rhythms that cause you to die," she explained.
While the findings need to be confirmed by a randomized, controlled trial before they can become firm recommendations, the general rule of replacing saturated fats with omega-3 fats is "a heart-healthy thing to do," Albert said. "The American Heart Association recommends that people eat fish twice a week."
"Green leafy vegetables should be included no matter what," Heller added. "The evidence is very compelling that omega-3 fatty acids are very healthy in many ways, including as a systemic anti-inflammatory agent and in the arteries. We need to include more of the omega-3s in the diet."
For more on women and heart disease, visit the American Heart Association.