The Heart Foundation is reported as saying "..there is international scientific consensus that replacing saturated fat with ... polyunsaturated fat, reduces your risk of heart disease."
REALLY? Thousands of scientists and many large rigorous, randomized clinical trials say otherwise.
1. The Minnesota Coronary Experiment, a large (9,570 subjects) rigorous trial of replacement of saturated fat with vegetable oil rich in linoleic acid found no difference. A decrease in cholesterol, yes, but NO improvement in survival. (post hoc it was noted that a sub-group of the linoleic acid patients had the highest risk of death)
2. The Sydney Diet Heart Study found that "substituting dietary linoleic acid in place of saturated fats increased the rates of death from all causes, coronary heart disease and cardiovascular disease"
3. The Mediterranean diet trial (Lancet 1994 June 11) Patients randomized to lower linoleic acid consumption (compared to a prudent diet) had a much lower mortality post infarct. This trial is also evidence that not all of your fat intake should be in the form of satutated fat. A diet with lots of saturated fat, but little omega-3 is bad.
4. A review published in the British Journal of Nutrition in 2010 found a trend for omega-6 supplementation to increase cardiovascular disease risk.
Many other studies suggest poor health outcomes from diets relatively high in linoleic acid. (see future posts) Not to mention common sense. Rational people have been following the right diet for decades, not just since 1994.
Of course some research seems to support the use of linoleic acid. This is not surprising because many foods high in linoleic acid also contain omega-3s, and consuming them will likely provide a benefit to someone whose omega-3 intake was previously too low. Next time you look at a study which allegedly supports the use of omega-6s, check whether the benefit was attributable to omega-3s. Also look at the end-point. Was it death or major cardiovascular event, or was it merely a change in serum rhubarb.
The Heart Foundation seems not to understand that the laws of syllogism do not necessarily apply to statistical associations. If A correlates with B, and B correlates with C, it is illogical to conclude that A correlates with C. That linoleic acid lowers cholesterol in some subgroups, and high cholesterol often correlates with cardiac events, does not allow one to conclude that linoleic acid reduces cardiac events.
Take home message - not all polyunsaturated fats are the same. Learn the difference. I suggest we leave the terms saturated and polyunsaturated fats to the chemists. There are such large differences in the health effects of different polyunsaturates that it is illogical to lump them together for dietary purposes. Same with saturated fats.