The publication of "Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis" in the British Medical Journal should be sobering news for twenty-first century public health advocates. The results of the biggest and most thorough study thus far to investigate what happens when people switch from animal fats to vegetable oils couldn’t be more clear. Those who heeded the advice to switch from saturated fats to polyunsaturated vegetable oils dramatically reduced their odds of living to see 2013.
What happened? Fifty years ago the medical community did an about-face (it had previously thought the evidence equivocal at best and so cautioned against jumping to conclusions) and instead went all in on polyunsaturated fats. It reasoned that since (a) cholesterol is associated with cardiovascular disease and (b) polyunsaturated fats reduce serum cholesterol levels, it inescapably followed that (c) changing people’s diet from saturated fats to polyunsaturated fats would save a lot of lives. In 1984 Uncle Sam got involved – Time magazine reported on it in "Hold the Eggs and Butter" – and he made a big push for citizens to swap out animal fat in their diet for the vegetable variety and a great experiment on the American people was begun.
Assuming the inferences drawn from the Sydney Diet Heart Study (~60% increase in risk of death by switching from animal fats to vegetable oils) apply to Americans and considering the population at risk of death from cardiovascular disease (~37% given recent NHANES data) we can’t think of any mass tort, or combination of mass torts, that has produced as much harm as the advice to change to a plant oil-based diet. Maybe some clever lawyer will find a way to use the tort system to quell the fervor of those armed only with a desire to do good and evidence of an association between something they don’t like and something else they don’t like. We won’t be holding our breath. But we will be hoping that those seeking to impose lean body styles and low salt diets on their fellow countrymen take a good long look at the polyunsaturated vegetable oil data before they order their riders to sally forth on the next crusade.