Substituting omega-6 linoleic acid in place of saturated fats increases death rates of heart disease patients, according to a study published in the British Medical Journal.
In a second analysis of The Sydney Diet Heart Study (SDHS), a randomized controlled trial, performed in Australia between 1996 and 1973, researchers from the United States and Australia calculated whether eating more safflower oil affected the risk of death in people with coronary heart disease (called "secondary prevention").
Researchers gathered 458 male participants between the ages of 30 and 59 years who had suffered a heart attack, an episode of coronary insufficiency or angina after admission to a hospital. Participants then were randomly assigned to a dietary intervention group or a control group without dietary intervention.
The dietary intervention group increased polyunsaturated fatty acid intake to about 15% of total energy intake, reduced saturated fatty acid intake to less than 10% of energy intake and reduced cholesterol to less than 300 mg per day. To achieve these targets, the men were given liquid safflower oil and safflower oil polyunsaturated margarine to replace animal fats, butter and margarine, shortenings, cooking oils and salad dressings, as well as taking the safflower oil as a supplement.
Participants were clinically assessed every three months over then first year, then every six months for a median of 39 months. Blood samples were taken to measure levels of cholesterol and triglycerides and participants kept food diaries for dietary assessment.
Results showed participants in the intervention group had a higher death rate (17.6%) compared to the control group death rate (11.8%). Also, an increase of 5% of food energy from omega-6 linoleic acid predicted a 35% higher risk of cardiovascular death and a 29% increase in all-cause mortality in the intervention group.
While other studies have shown omega-6 fatty acids to be good for heart health, this cohort concluded that substituting omega-6 linoleic acid in place of saturated fatty acids increased the risk of death from all causes, coronary heart disease and cardiovascular disease.
