"The authors state that the study assessed the effects of replacing saturated fat in the diet with omega 6 polyunsaturated fats, but it doesn’t.
The study used Miracle margarine as a source of polyunsaturated fat. In the 1960s, when this study began, Miracle margarine contained approximately 15% trans fatty acids, which have the worst effect on heart disease risk of any fat. The adverse effect of the intervention in this study was almost certainly due to the increase in trans fatty acids in the diet. Recent, well conducted studies indicate that replacing saturated fat with polyunsaturated fats lowers heart disease risk and this is widely accepted. Trans fatty acids were largely removed from Australian margarines in the mid-1990s when their adverse effects on heart health became apparent.”
--Bill Shrapnel
“This is a very small study with only 63 total deaths. The 5.8% difference between groups for total mortality represents a difference of 10 deaths between groups (p=0.051) computed from the % deaths which does not meet conventional statistical significance. Figure 1 though only shows a difference in 6 deaths between groups. Certainly there is no evidence of benefit but the evidence of harm is relatively weak. Although dismissed by the authors trans fats are likely to be responsible for the lack of benefit. The margarine would have contained at least 20% trans fatty acids and if the participants were eating 25g/day of margarine then they would be consuming 5g of trans which might represent about 2% of calories. From the Nurses Health study this could reduce heart disease by 40-50% which would almost completely remove the apparent increased risk from the N6 margarines. The more margarine eaten the greater the risk. The test margarine would have mostly supplanted butter rather than other margarines. The fall in total cholesterol seen not only reflects a fall in LDL cholesterol but also a trans induced fall in HDL cholesterol.
"The fact that an increase in PUFA in the control group (90% of which would have been N6) was not associated with harm suggests the findings in the intervention group are confounded by the trans fats.”
--Peter Clifton
"This is data dredging of a study conducted many years ago in Australia. It has little relevance to diets today. It reports the results of a study conducted in Sydney where subjects were asked to consume large amounts of safflower oil. The study was stopped because of adverse effects – I heard about this from a colleague whose brother was involved in the trial more than 30 years ago! Hopefully science has moved on. Firstly, the study was enormously underpowered to detect any meaningful outcome with only 458 men. Assuming a high mortality of 12% per year, the chances of detecting meaningful differences in mortality are small, particularly when follow-up is short".
-Tom Sanders
