For a long time, nutrition experts have told us to replace saturated fats (solid at room temperature) with polyunsaturated fats (liquid at room temperature). One polyunsaturated fat is omega-6. Omega-6 is found in large amounts in corn oil, soybean oil, and most other vegetable oils (flaxseed oil is the big exception). According to Eat Drink and Be Healthy (2001) by Walter Willett (and “co-developed with the Harvard School of Public Health”), “replacing saturated fats with unsaturated fats is a safe, proven, and delicious way to cut the rates of heart disease” (p. 71). “Plenty of proof for the benefits of unsaturated fats” says a paragraph heading (p. 71). Willett failed to distinguish between omega-3 and omega-6.
A recent study in the BMJ shows how wrong Willett (and thousands like him) were. This study began with the assumption that omega-3 and omega-6 might have different effects, so it was a good idea to try to measure the effect of omega-6 separately.
They reanalyzed data from a study done in Sydney Australia from 1966 to 1973.The study had two groups: (a) a group of men not told to change their diet and (b) a group of men told to eat more omega-6 by eating more safflower oil (and reducing saturated fat intake, keeping overall fat intake roughly constant). The hope was that the change would reduce heart disease, as everyone said.
As these studies go, it was relatively small, only about 500 subjects. The main results:
Compared with the control group, the intervention group had an increased risk of all cause mortality (17.6% v 11.8% [emphasis added]; hazard ratio 1.62 (95% confidence interval 1.00 to 2.64); P=0.051), cardiovascular mortality (17.2% v 11.0%; 1.70 (1.03 to 2.80); P=0.037), and mortality from coronary heart disease (16.3% v 10.1%; 1.74 (1.04 to 2.92); P=0.036).
A 50% increase in death rate! The safflower oil was so damaging that even this small study yielded significant differences.
The authors go on to show that this result (omega-6 is bad for you) is supported by other studies. Walter Willett and countless other experts were quite wrong on the biggest health issue of our time (how to reduce heart disease, the #1 cause of death).