Saturated

LET’S MOVE ON FROM OUTDATED FACTS ABOUT FAT.

Every field of human activity or thought has its liberals and its conservatives: this is as true of diet science as it is of NHL fandom or appliance design or poker. This week a trio of renowned cardiologists has made world headlines with an editorial appearing in the British Journal of Sports Medicine. Their short article was meant to stir up trouble, trouble they surely welcome. It is intentionally radical, born from frustration with the persistence of harmful myths about food.

You are probably a prisoner of these myths, as I am. If you still look slightly askance at an egg because of the “cholesterol” in it, or if you have recently described or thought of a hamburger as “artery-clogging,” you are in the trap. “The conceptual model of dietary saturated fat clogging a pipe,” say the BJSM cardiologists, “is just plain wrong.”

Most of us grew up with, and have not surrendered, a folk version of that model: saturated fats in dairy and meat raise your cholesterol, which then settles into your arteries like a sludge and makes you die young and miss your kids’ graduations.

But most of the theoretical links that went into the old diet- heart model have been discredited or become uncertain. Doctors have learned to distinguish between levels of “bad” and “good” cholesterol when assessing patients for cardiovascular risk. And plenty of theoreticians now doubt whether there is any point at all in nutritional recommendations about cholesterol consumption. Coronary thrombosis is caused by cholesterol deposits in the walls of one’s arteries, but, as the authors of the BJSM editorial say, the way in which they cause harm is more like the bursting of a pimple than a “clogging”— which is why preventive arterial stenting for cardiovascular health has not panned out well.

The BJSM editorial mentions two legendary papers that appeared in the British Medical Journal in February 2013 and April 2016. These papers are already landmarks of epidemiology. They were written by a team of researchers who have been going back to major diet-heart studies of the past and retrieving the original data from dusty folders and magnetic tapes, in order to review them using contemporary analytical techniques. They are, in short, cold- case detectives.

Their first target was the Sydney Diet Heart Study (1966-73), in which 458 middle- aged coronary patients were split into a control group and an experimental group. The latter group was fed loads of “healthy” safflower oil and safflower margarine in place of saturated fats. Even at the time it was noticed that the margarineeaters died sooner, although their total cholesterol levels went down: the investigators sort of shrugged and wrote that heart patients “are not a good choice for testing the lipid hypothesis.” Their data, looked at now, shows that the increased mortality in the margarine group was attributable specifically to heart problems.

The team’s reanalysis of the Minnesota Coronary Experiment ( 1968-73) is more hair- raising. This study involved nearly 10,000 Minnesotans at old-age homes and mental hospitals. The investigators had near- complete control of the subjects’ diets, and were able to autopsy the ones who died. But much of their data, including the autopsy results, ended up misplaced or ignored. Some of it disappeared into a master’s thesis by a young statistician, now a retired older chap, who helped with the 2016 paper and is named at its head as one of the authors.

In the Minnesota study, replacement of saturated fats with corn oil led, again, to reductions in total cholesterol. This finding was touted at major conferences, and it became one of the key moments in the creation of the classic diet-heart myth. This time nobody but the guy who wrote the thesis even noticed that the patients in the corn oil group were, overall, dying a little faster. The 2016 re-analysis uncovered a dose-response relationship: the more the patients’ total cholesterol decreased, the faster they died.

The Sydney and Minnesota studies themselves may have caused a few premature deaths, which is a possibility we accept as the price of science. But the limitations and omissions of the researchers, and the premature commitment of doctors to a total-cholesterol model, helped create a suspicion of saturated fats. This flooded into frontline medical advice and the wider culture, and it put margarine on millions of tables, pushed consumers toward deadly trans fats, and put millions of people with innately high cholesterol levels through useless diet austerity. The scale of the error is numbing, unfathomable.

The cardiologists who wrote the new paper have updated advice for eaters: try the “Mediterranean diet,” which allows for lots of olive oil, fat- rich nuts, and oily fish. And engage often in brisk walks. Don’t count fat; don’t fret over what kind of fat you’re getting, per se. Just go for walks and eat real food.

Naturally, the authors are facing a backlash from “conservatives,” attached to the old ways. The detractors worry that the Mediterranean diet is easy to get wrong outside the Mediterranean. They fret that people will perceive the death of the saturated- fat myth as a licence to eat ice cream until they explode. It is not so much an argument about the facts as it is about “messaging.” Which is depressingly typical when it comes to nutritional science.