Good News on Saturated Fat

Should we be reconsidering the conventional wisdom on saturated fat? Yes, according to Gary Taubes’s interpretation of the new report in The New England Journal of Medicine on a two-year diet experiment in Israel.

The Israeli researchers found that people on a relatively low-fat diet lost less weight (6 pounds) than those who ate a low-carbohydrate or Mediterranean diet (10 pounds). These relatively modest weight losses were interpreted as discouraging news for dieters, and they also set off a debate on whether the whether the low-carb diet was really an Atkins-style diet, as my colleague Tara Parker-Pope reported.

Mr. Taubes prefers to focus on another aspect of the study: perhaps the best news yet about saturated fat. As I wrote last year, in a column about Mr. Taubes and his book “Good Calories, Bad Calories,” the medical establishment originally warned people to avoid all kinds of fat, but subsequent studies kept failing to produce evidence of the benefits of a low-fat diet. Then the supposed experts said the villain wasn’t just any fat but specifically saturated fat. But now their recommendations are being undermined yet again by research, Mr. Taubes says. Here’s his take on the new experiment and a series of similar trials:

These trials are fundamentally tests of the hypothesis that saturated fat is bad for cholesterol and bad for the heart. They’re not just about which diet works best for weight loss or is healthiest, but what constitutes a healthy diet, period. (This is the point I made in my Times Magazine story six years ago). Specifically, these low-fat/low-carb diet trials, of which there are now more than half a dozen, test American Heart Association (A.H.A.) relatively low-fat diets against Atkins-like high-saturated-fat diets.

In this last test, the A.H.A. diet was about 30 percent calories from fat, less than 10 percent calories from saturated fat; the low-carb diet was almost 40 percent calories from fat, around 12.5 percent saturated fat. In this particular trial, as in all of them so far, the high-saturated-fat diet (low-carb or Atkins-like) resulted in the best improvement in cholesterol profile — total cholesterol/H.D.L. In this Israeli trial, the high-saturated-fat diet reduced L.D.L. at least as well as the did the A.H.A. relatively low-fat diet, the fundamental purpose of which is to lower L.D.L. by reducing the saturated fat content.

So here’s the simple question and the point: how can saturated fat be bad for us if a high saturated fat diet lowers L.D.L. at least as well as a diet that has 20 to 25 percent less saturated fat?

It could be argued (and probably will be) that the effect of the saturated fat is confounded by the reduction in calories, but the A.H.A. diet also reduces calories and in fact specifies caloric reduction while the low-carb diet does not. It will also be argued, as Dean Ornish does, that the source of the saturated fat was not necessarily meat or bacon, but beans or other healthy sources.

But the nutritional reason why meat has been vilified over the years, is that it’s a source of unhealthy saturated fat. It’s not that meat per se is bad — unless you buy the colon cancer evidence, which has always seemed dubious — it’s that the saturated fat in meat makes it bad. So the argument about the source of the saturated fat is irrelevant.

The question hinges on whether saturated fat raises cholesterol and causes heart disease. One way or the other this trial is a test of that hypothesis. It’s arguably the best such trial ever done and the most rigorous. To me that’s always been the story. If saturated fat is bad for us, then these trials should demonstrate it. They imply the opposite.

Why does the A.H.A. continue to insist that saturated fat should be avoided, if these trials repeatedly show that high saturated fat diets lead to better cholesterol profiles than low-saturated fat diets? And how many of these trials have to be done before the National Institutes of Health or some other august institution in this business re-assesses this question? After all, the reason the food guide pyramid suggests we eat things like butter and lard and meats sparingly (and puts them high up in the pyramid) is that they contain saturated fat. This is also the reason that the A.H.A. wants to lower even further what’s considered the safe limit for saturated fats in the diet.

Is Mr. Taubes right? If eating more saturated fat improved the dieters’ cholesterol profile (while also enabling them to lose weight even though their calories were not restricted), should the federal government and the American Heart Association stop warning people about saturated fats?