Since the 1970’s, we’ve reduced our sugar, salt, and saturated fat intake, and we’ve dramatically reduced our rates of smoking, high serum cholesterol and high blood pressure. At the same time, rates of chronic disease, including coronary heart disease, have increased—in some cases, dramatically.
The best that we can say is that since the 1970s, rates of myocardial infarction have decreased slightly—but only in white folks.
If the current health prescription is valid, then we should see dramatic differences in rates of disease and mortality between those who follow the prescription and those who don’t, and we should see clear and strong associations between “healthy” food choices and good health (because the same people eating a “healthy” diet are also taking care of their health in other ways). Yet this is not what we see.
Is it possible that our low-fat diet has removed some protective factors from our nutritional profile and exposed us to increased levels of nutrients that have negative impacts on health? I think it is, and a recent study in BMJ supports this notion.
I am a long-time admirer of one of the researchers, Daisy Zamora, and she is a good friend of mine. She’d been dropping hints about this great study she was working on for a while now—but was sworn to secrecy and now I know why. What she and her co-investigators have uncovered is data from a long-ago diet study, conducted from 1966-1973. It’s a decently large, well-run, randomized controlled trial that replaces saturated fat with safflower oil, a vegetable oil particularly high in one kind of PUFA—omega-6 (n-6) linoleic acid—and low in another kind of PUFA—omega-3 (n-3) alpha linolenic acid. The idea was that replacing “bad” saturated fat with “healthy” vegetable oil in men with premature coronary heart disease would improve survival. This did not turn out to be the case. For some reason, though, the original study only reported all-cause mortality and not deaths from cardiovascular disease and coronary heart disease.
Daisy and her co-investigators climbed into their way-back machine and this is what they found: Not only did the participants in the intervention group have an increased risk of all-cause mortality, but they had an increased risk of death from cardiovascular disease and coronary heart disease.
Although the switch to safflower oil did lower total cholesterol, these reductions didn’t help those participants live any longer than those who kept eating saturated fat. In fact, as the authors note, “the increased risk of death in the intervention group presented fairly rapidly and persisted throughout the trial.” (Hmm. Maybe this whole “cholesterol lowering” thing isn’t as important as we thought.)
Furthermore, the authors go on to point out that the relationship between linoleic acid consumption and increased mortality was particularly robust in smokers and drinkers, “suggesting that diets high in n-6 [linoleic acid] may be particularly detrimental in the context of oxidative stress induced by smoking and alcohol.”
Everyone knows that if you are a smoker you should quit and that alcohol should be used in moderation. But, with this evidence in mind, if you decided to keep on smoking and/or you want to drink immoderately, you may want to consider a breakfast of eggs and bacon rather than whole wheat toast and “heart healthy” margarine before you do.
The entire article is available online. Read it for yourself and see what you think. Anybody besides me wondering how the American Heart Association will respond to this study?