Have you ever heard the saying “you can’t teach an old dog new tricks”? It’s not true. Many old dogs learn new tricks with the right training and motivation.
It turns out that it could be a lot harder to teach old docs new tricks, especially when it comes to nutrition. Even though medical schools taught very little nutrition science decades ago, some physicians just can’t let go of the lessons they learned.
What Did Doctors Learn About Nutrition?
During the middle of the 20th century, medical students were told that fat in general and saturated fat in particular caused high cholesterol. It was seen as the driving force behind heart attacks. Patients were urged to switch to margarine instead of butter, cut back on eggs and cheese and forego ice cream and burgers. After all, the thinking went, these foods are high in cholesterol and cholesterol is found in plaque in arteries.
Dietitians often recommended a “heart-healthy” breakfast of cornflakes with skim milk, toast with margarine and a glass of orange juice. Another option might be pancakes cooked on a nonstick griddle.
Margarine vs. Butter:
Before the century closed, nutrition science had found that margarine with its trans fats was actually causing more harm than butter. But health professionals have been reluctant to give up on fat as a dietary demon. That is why low-fat products like skim milk and non-fat yogurt dominate the dairy case. The American Heart Association still advises patients to limit saturated fat and select skim and low-fat dairy products.
New Data from a PURE Nutrition Study:
Now, however, the definition of healthy eating is shifting, based on actual data. Recent research called the Prospective Urban Rural Epidemiology (PURE) study carefully collected dietary information from 135,000 people (Dehghan et al, The Lancet, online Aug. 29, 2017). After seven years, almost 6,000 people had died and more than 4,700 had suffered heart attacks or strokes.
High-Carb Diets Were More Dangerous:
Analysis showed that the people who had been eating a high-carbohydrate diet were more likely to end up among the deceased or diseased. Those whose diets were richer in fat were less likely to have died. One particular correlation stands out: those consuming more saturated fat were at lower risk for strokes.
Previous Studies on Saturated Fat:
This is not the first study to suggest that saturated fat is not our enemy. The Minnesota Coronary Experiment ran from 1968 till 1973. In this randomized controlled trial, 9,000 patients were served meals high in saturated fat or unsaturated vegetable oil. The corn oil lowered cholesterol but did not improve survival. If anything, those eating corn oil were somewhat more likely to die (Ramsden et al, BMJ, April 13, 2016).
Another classic trial had similar results. The Sydney Heart Study randomized 458 Australian heart attack survivors to continue on their usual 1960s diet high in saturated fat or to substitute safflower oil for sat fat. The data were not published at the time, but the men on the low sat fat diet were more likely to have heart attacks and die (Ramsden et al, BMJ, Feb. 5, 2013).
Rethinking Nutrition Dogma on Saturated Fat:
These findings led the investigators to question the diet-heart hypothesis so esteemed in nutrition circles. As new data (as well as new analysis of old data) demonstrate that old dietary beliefs were mistaken, health professionals need to rethink their advice. (Indeed, a few have begun to do so.) Sugar and other highly processed carbohydrates appear to be more hazardous to health than fat.
We have spoken with several physicians who have become convinced that we need to worry more about refined carbohydrates and sugar in our diets than about minimally processed fat. You can listen to our interviews with Dr. Robert Lustig, author of Fat Chance; Dr. Jacob Teitelbaum, author of The Complete Guide to Beating Sugar Addiction; and Dr. David Ludwig, author of Always Hungry.