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(Last updated 5/27/99)
5/28/99
FATTY ACIDS IN VEGETABLE, FISH OILS MAY AVERT FATAL HEART ATTACKS
COLUMBUS, Ohio -- Three types of fatty acids found in fish oils and vegetable oils may one day help protect people from having fatal heart attacks, according to a new study.
The three fatty acids -- known as omega-3 polyunsaturated fatty acids -- seem to make heart attacks less deadly by balancing the electrical rhythms in the heart and preventing blood clots from forming.
George E. Billman, professor of physiology at Ohio State University, said that the fatty acids make the tissues in the muscles of the heart less susceptible to damage caused by cardiac ischemia, or lack of blood. This lack of blood flow may occur when a major artery is blocked by fatty deposits, or plaques.
“It looks like omega-3 fatty acids protect against the changes induced by ischemia,” said Billman.
Every year in the United States, approximately 250,000 people die suddenly, probably as the result of sudden ischemic arrhythmias.
Billman, along with researchers at Massachusetts General Hospital and Harvard University Medical School, published the results of the study in a recent issue of the journal Circulation.
The researchers gave 17 dogs who were susceptible to cardiac arrhythmias infusions of one of three essential dietary fatty acids. Two of the fatty acids are found in fish oils such as tuna fish oil: eicosapentaenoic acid (EPA for short) and docosahexaenoic acid (DHA). The other, alpha-linolenic acid (LNA), is present in some vegetable oils, such as safflower oil and sunflower seed oil.
The dogs ran on a treadmill for an average of 18 minutes, until they reached 70 percent of their maximum heartbeat and experienced an arrhythmia known as ventricular fibrillation.
With infusion of the EPA fatty acid, five of seven dogs were protected from fatal ventricular arrhythmias. With the DHA fatty acid, six of eight dogs were protected. With LNA fatty acid, another six of eight dogs were protected.
Researchers have known for years that certain fish oils and vegetable oils seem to prevent heart disease when included in a healthy diet. This study tested whether the purified forms of the omega-3 fatty acids in these oils prevented fatal arrhythmias. This should help enable researchers to pick out the active ingredients in the oils responsible for the protective effect.
Billman thinks that heart muscle cells absorb the fatty acids. When an arrhythmia occurs, the cells release the fatty acids, which balance the ions entering the heart cells. These ions are responsible for the electrical activity of the heart. In addition, the fatty acids could balance the nerve impulses that govern heartbeat.
Parasympathetic nerve impulses decrease heart rate while the sympathetic impulses increase it. Animals prone to arrhythmia have a high incidence of sympathetic impulses and a low incidence of parasympathetic impulses.
“The sympathetic nerve impulses work like the accelerator on a car while the parasympathetic impulses are the breaks,” Billman said.
Regular exercise increases parasympathetic activity, and drugs that mimic parasympathetic activity or block sympathetic activity can prevent ventricular arrhythmias. The omega-3 fatty acids in this study appeared to do the work of anti-arrhythmic drugs.
According to Billman, the results indicate that taking a dietary supplement of one of these fatty acids might give people the same benefit as eating foods containing the fatty acids.
“It’s hard for people to change their diets,” he said. “This would be a pill they could take once a day.”
Unlike other anti-arrhythmic drugs, natural fatty acids have no side effects except for slowing the formation of blood clots. Billman warned that people prone to ulcers might not want to take a fatty acid supplement.
This work was funded by the American Heart Association, Ohio Valley Affiliate, and the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.
Contact: George E. Billman, (614) 292-5189; Billman.1@osu.edu
Written by Pam Frost, (614) 292-9475; Frost.18@osu.edu