By Ed Edelson
Monday, January 26, 2009 12:00 AM
MONDAY, Jan. 26 (HealthDay News) -- All that discussion about the omega-6 fatty acids found in vegetable oils, nuts and seeds possibly being bad for your heart is unfounded, a new science advisory from the American Heart Association claims.
"There has been a lot of talk in the nutrition world that omega-6 fatty acids might be bad," said William S. Harris, the nutritionist heading the committee that issued the report in the Jan. 26 online issue of Circulation. "We wanted to evaluate it, and if it is not true, we wanted to make sure the American public eats enough of them."
The debate arose because arachidonic acid, a component of omega-6 fatty acids, is a building block for some inflammation-related molecules, and there have been fears that it might increase the risk of heart disease.
"That reflects a rather naive understanding of the biochemistry," said Harris, who is director of the Metabolism and Nutrition Research Center of the University of South Dakota Sanford School of Medicine. "Omega-6 fatty acids give rise to both pro-inflammatory compounds and anti-inflammatory compounds. To say that they are bad because they produce pro-inflammatory compounds ignores the fact that they give rise to anti-inflammatory compounds as well."
The major component of omega-6 fatty acids is linoleic acid, accounting for 85 percent to 90 percent of the total. Both linoleic acid and arachidonic acid give rise to pro-inflammatory and anti-inflammatory molecules, the journal report noted.
The advisory says that people should aim at getting at least 5 percent to 10 percent of their calories from omega-6 fatty acids which, like the omega-3 fatty acids found in some fish, are polyunsaturated. These PUFAs -- polyunsaturated fatty acids -- play crucial roles in growth and development and have a protective value if they replace saturated fats that can collect in arteries to form plaques that limit blood flow.
The committee headed by Harris conducted a two-year assessment looking at more than two dozen controlled and observational studies. Observational studies found that people who ate the most omega-6 fatty acids generally had a lower incidence of heart disease. In controlled trials, participants assigned to diets higher in omega-6 fatty acids had less heart disease.
The recommended daily intake of omega-6 fatty acids ranges from 12 grams to 22 grams a day, depending on age, gender and level of physical activity.
Harris said he meets those guidelines without much effort. "I keep to pretty much the standard American diet," he said. "I use salad dressing, one of the most common sources of vegetable oils, which have omega-6 fatty acids in their most concentrated forms."
Omega-6 fatty acids are also found in many baked goods and some foods that are fried with those acids. "Nuts do provide a good amount of omega-6, but not all oils," Harris said. "Canola oil and olive oil are low in omega-6, but corn oil is good."
Dr. Robert H. Eckel, a professor of medicine at the University of Colorado and a past president of the American Heart Association, said he avoids talking about percentages when asked about omega-6 fatty acid intake.
"Most patients don't want to hear about percentages," Eckel said. "I really emphasize maintaining an overall healthy diet." If asked, Eckel points out that vegetable oils, nuts and seeds are good sources of omega-6 fatty acids.
"There has been a lot of talk about this concern," Eckel said. "I'm glad that the American Heart Association went ahead and looked into the evidence of such a harmful effect, and it just isn't there. This will comfort everyone who likes vegetable oil as part of a healthy diet."
For more on good fats vs. bad fats, visit the American Heart Association.
SOURCES: William S. Harris, Ph.D., director, Metabolism and Nutrition Research Center, University of South Dakota Sanford School of Medicine, Sioux Falls, S.D.; Robert H. Eckel, M.D., professor, medicine, University of Colorado, Denver; Jan. 26, 2009, Circulation, online; Feb. 17, 2009, Circulation, print edition