Replacing animal fats with vegetable oils, a mainstay of modern health advice, may lead to an increased risk of death among people with heart disease, according to an analysis of data gathered 40 years ago.
In a study of 458 men, those who had experienced a heart attack or other coronary event and replaced saturated fats with omega-6 polyunsaturated fats found in corn, sunflower and safflower oil had a 16 percent rate of death from heart disease, compared with 10 percent for those who didn’t get dietary advice, researchers found.
The new analysis, funded by the National Institutes of Health, challenges a cornerstone of dietary advice backed by the American Heart Association that favors replacing saturated fats with omega-6 polyunsaturated fats.
“These findings argue against the ‘saturated fat bad, omega 6 polyunsaturated fat good’ dogma,” said Philip Calder, professor of nutritional immunology at the University of Southampton, in an editorial accompanying the study publication. The American Heart Association’s advisory “may be misguided.”
The analysis of research in Australia recovered data from the Sydney Diet Heart Study conducted from 1966 to 1973, which didn’t report deaths due to cardiovascular disease and coronary heart disease. It was published today in the British Medical Journal.
The association’s scientific advisories “are based on careful analysis of peer-reviewed studies” reviewed by a team of experts who reach conclusions based on the full body of scientific evidence, the American Heart Association says on its website. The current guideline recommends that most people consume at least 5 percent of their total daily calories from omega-6 fatty acids.
The analysis published today may not invalidate switching to fats found in some of the most common vegetable oils, according to some researchers.
“These are typically 50-year-old men, mainly smokers, who have had a heart attack already, and there were only 63 deaths altogether,” said David Spiegelhalter, Winton Professor of the Public Understanding of Risk at the University of Cambridge. “So I would not want to get very excited about this study on its own.”
How the study was designed should also be scrutinized, said Tom Sanders, professor and head of King’s College London’s diabetes and nutritional sciences division. Safflower oil polyunsaturated margarine was provided to subjects as a substitute for butter and common margarines.
“We do not know the level of trans fatty acids in the margarine, which are now known to increase risk of heart disease,” Sanders said. “Current advice should be based on present knowledge and not veered off course by this new study.”