Dietitians have been encouraging Americans to substitute vegetable oil for saturated fats such as butter and lard. The assumption has been that polyunsaturated fatty acids found in oils such as safflower and corn would lower cholesterol and help prevent heart disease.
Although such oils do lower cholesterol, a new analysis from data collected almost 50 years ago shows that increasing the amount of fatty acids from safflower oil may backfire. The Sydney Diet Heart Study was a controlled trial carried out between 1966 and 1973. The Australian men in this study had already had one coronary event. They were randomly assigned to maintain their regular diet or substitute liquid safflower oil and safflower-based margarine.
The men who consumed safflower oil instead of butter did lower their cholesterol, but they were at significantly greater risk of death during the study. They were 70% more likely to die of cardiovascular disease and 75% more likely to die of a coronary. The original study had not analyzed heart disease deaths separately by group. These striking results suggest that overloading the diet on polyunsaturated vegetable oils could be counterproductive.
BMJ, online, Feb. 5, 2013]