I came across a remarkable paper today, published in the American Journal of Medicine, and remarkably (!) fully available online.
Two MD authors, James E. Dalen, MPH and Stephen Devries, FACC, summarize carefully and clearly 56 years of nutrition studies investigating the diet heart hypothesis.
In 1957 Ancel Keys noted a linear correlation between dietary fat and cardiovascular disease, and presumed the mediating influence to be elevated serum cholesterol. Good scientists knew that correlation does not prove causation and we set off chasing our tails for 50+ years and many folks are still in that impossible endeavor. The earliest studies did not confirm Keys’ hypothesis, so the experimental model shifted. “Ahah! It must not be reduced overall fat, but rather reduced saturated and increased polyunsaturated that is the key to good health!” Indeed, many if not most folks still believe this is true.
But that coffin has actually been nailed shut.
As the good doctors point out, the big and final nail was the infamous MRFIT study in which there were essentially two groups. One group ate the American Heart Association diet. They stayed at less than 30% calories from fat, less than 10% from saturated fat and less than 300 mg daily of cholesterol. (For the sake of comparison, one egg has 200+ mg of cholesterol; I’ve had four so far today, how about you?) They also benefitted from excellent blood pressure control and more successful efforts to curtail smoking. They should have far surpassed the “control group” who ate normally and did not have their other lifestyle habits so well treated. But both groups ended up with the same degree and severity of heart disease.
Meaning, essentially that the “normal eating” with higher fat and more eggs, must have been protected by their diet against the deleterious effects of hypertension and smoking. I love that observation, and must admit it has not been fully tested so it survives only as a theory.
Let me quote the doctors’ summary:
Despite the significant reductions in dietary fat, the changes in total cholesterol and LDL cholesterol after seven years of intervention were modest. … The end points of reduction in total mortality and coronary death were not achieved… striking given that hypertension was better controlled and cigarette cessation more successful in the special intervention group.
Research scientists changed tack again, and returned to Keys’ observations without presuming that fat was the problem, knowing only that Mediterranean countries fared better. Several clinical trials involving the full Mediterranean diet (which allows more fat, lots of fruits and vegetables, emphasizes leafy green vegetables, fish, poultry, but allows red meat, whole grains and legumes) have shown improved heart health and overall survival.
The study remaining to be done is one that lets people eat a Mediterranean diet and encourages saturated fat and dietary cholesterol from healthy sources: pasture-raised red meat, dairy and eggs. I officially volunteer for that one.
For today though we can hope that everyone’s physician takes a good look at this study and talks more about whole food and less about statins and serum cholesterol.