Free fatty acids are released from the body's fat cells and serve as fuel for heart cells, says lead study author Dr. Xavier Jouven, a cardiologist at the Georges Pompidou European Hospital in Paris. When blood levels of fatty acids become too high, he says they can cause arrhythmia, an irregular heartbeat that can stop the heart and cause death.
"This effect has been shown in patients with myocardial infarctions [heart attacks]. It has also been shown in rats. The point is that we have now shown this effect in a general population of healthy people," Jouven says.
The finding appears in the Aug. 14 issue of Circulation: Journal of the American Heart Association.
The study included 5,250 French civil servants, men aged 42 to 53 when they enrolled in the Paris Prospective Study. They were followed for an average of 22 years during which their free fatty acid levels were measured.
Over the years, the risk of sudden death was related to those fatty acid readings. Men with the highest levels were at a 30 percent increased risk, the study found.
While fatty acid levels were not directly related to heart attacks, Jouven says in some cases the arrhythmia triggered by high levels of fatty acids turned an otherwise survivable heart attack into a fatal one. In other cases, the cause of sudden death was ventricular fibrillation, a violent disturbance of heart rhythm that can occur independent of a heart attack.
Dr. Alexander Leaf, professor of clinical medicine at Harvard Medical School and author of an accompanying editorial, says the culprits probably was an overabundance of omega-6 fatty acids that come from meat and dairy products. An arrhythmias is more likely to occur if blood levels of omega-6 fatty acids are not in balance with levels of omega-3 fatty acids that come from other sources such as fish, he says.
"We know pretty much now which fatty acids cause arrhythmias when their level increases. The fatty acids that seem to be protective are the omega-3 fatty acids." says Leaf.
Jouven says his study cannot confirm that relationship, since levels of specific fatty acids were not measured in the participants.
However, he says, "From the medical literature, we know that when people eat fish rich in omega-3 fatty acids, they have a lower risk of sudden death." Blood levels of fatty acids can be why one person will survive a heart attack that is fatal to another, he says.
Measuring fatty acid blood levels could be clinically useful, since "we don't have many markers for the risk of sudden death. The markers we now use are the same as those for myocardial infarction," Jouven says.
What To Do
The American Heart Association recently revised its dietary advice, recommending at least two meals a week of fish rich in omega-3 fatty acids, such as tuna and salmon, in an overall diet focused on fruits, vegetables, whole grains, low-fat dairy products and lean meats and poultry.