What if Bad Fat is Actually Good for You?

ADVERTISEMENTSuppose you were forced to live on a diet of red meat and whole milk. A diet that, all told, was at least 60 percent fat -- about half of it saturated. If your first thoughts are of statins and stents, you may want to consider the curious case of the Masai, a nomadic tribe in Kenya and Tanzania.

In the 1960s, a Vanderbilt University scientist named George Mann, M.D., found that Masai men consumed this very diet (supplemented with blood from the cattle they herded). Yet these nomads, who were also very lean, had some of the lowest levels of cholesterol ever measured and were virtually free of heart disease.

Scientists, confused by the finding, argued that the tribe must have certain genetic protections against developing high cholesterol. But when British researchers monitored a group of Masai men who moved to Nairobi and began consuming a more modern diet, they discovered that the men's cholesterol subsequently skyrocketed.

Similar observations were made of the Samburu -- another Kenyan tribe -- as well as the Fulani of Nigeria. While the findings from these cultures seem to contradict the fact that eating saturated fat leads to heart disease, it may surprise you to know that this "fact" isn't a fact at all. It is, more accurately, a hypothesis from the 1950s that's never been proved.

The first scientific indictment of saturated fat came in 1953. That's the year a physiologist named Ancel Keys, Ph.D., published a highly influential paper titled "Atherosclerosis, a Problem in Newer Public Health." Keys wrote that while the total death rate in the United States was declining, the number of deaths due to heart disease was steadily climbing. And to explain why, he presented a comparison of fat intake and heart disease mortality in six countries: the United States, Canada, Australia, England, Italy, and Japan.

The Americans ate the most fat and had the greatest number of deaths from heart disease; the Japanese ate the least fat and had the fewest deaths from heart disease. The other countries fell neatly in between. The higher the fat intake, according to national diet surveys, the higher the rate of heart disease. And vice versa. Keys called this correlation a "remarkable relationship" and began to publicly hypothesize that consumption of fat- causes heart disease. This became known as the diet-heart hypothesis.

At the time, plenty of scientists were skeptical of Keys's assertions. One such critic was Jacob Yerushalmy, Ph.D., founder of the biostatistics graduate program at the University of California at Berkeley. In a 1957 paper, Yerushalmy pointed out that while data from the six countries Keys examined seemed to support the diet-heart hypothesis, statistics were actually available for 22 countries. And when all 22 were analyzed, the apparent link between fat consumption and heart disease disappeared. For example, the death rate from heart disease in Finland was 24 times that of Mexico, even though fat-consumption rates in the two nations were similar.