Friday, March 18, 2011

Historical Context, Part 3 - Ancel Keys

Ancel Keys, a University of Minnesota physiologist, deserves much of the credit for convincing the public that dietary fat and cholesterol are killers.  He initially became famous through his development of the "K-ration" for feeding combat troops in World War II; the "K" stood for Keys.  He then performed a series of human starvation studies and wrote the book "The Biology of Human Starvation", which made him a well-known, reputable nutrition researcher.  Originally, Keys did not believe dietary fat and cholesterol had anything to do with the rising heart disease rates, but his opinion changed when he attended a conference in Rome in 1951, where he spoke with a physiologist from Naples, Italy who boasted about the lack of heart disease in his city.  The diet in southern Italy was low in animal products, and the people there, especially the poor, tended to have lower cholesterol than those in the United States.  The rich in Naples, however, ate more meat, and had higher cholesterol levels and heart disease rates.  This convinced Keys for the first time that dietary fat from meat was driving the heart disease epidemic in the United States.

There were two key observational studies performed by Ancel Keys that ended up having an impact on the public's view of dietary fat.  The first, which many researchers did not taken seriously, was the 1953 study he performed involving six countries, comparing their fat intake to their heart disease rates.  The six countries he reported on (United States, Canada, Australia, UK, Italy, and Japan), showed a very strong association between fat intake and heart disease.  Now, of course, this is only an observational study and no cause and effect can be determined.  But the biggest problem with his study is that he left out the data from the 16 other countries for which data was available.  When all 22 countries are considered, his perfect correlation turns into a much weaker one.

Initially, in 1957, the American Heart Association (AHA) opposed Ancel Keys on the diet-heart hypothesis.  They wrote a 15-page report that year denouncing Keys and similar researchers for jumping to conclusions about the diet-heart hypothesis when there was no good evidence that it was true.  Less than four years later, in December of 1960, the AHA flipped their stance and adopted the diet-heart hypothesis as their new philosophy on heart health, proclaiming that "the best scientific evidence of the time" strongly suggested a low-fat diet, or at least replacing saturated fats with polyunsaturated fats, is preventative of heart disease.  What had changed in that four-year period?  Not the evidence.  There was no new evidence to either confirm or reject the diet-heart hypothesis.  What had changed is that Ancel Keys and Jeremiah Stamler, another supporter of Keys, had now made up two of the six members on the AHA committee.  Soon after, Ancel Keys was enshrined as the face of dietary wisdom in America in an article in Time magazine.  The article discussed Keys' idea of a heart-healthy diet as one in which nearly 70% of calories came from carbohydrates and just 15% from fat.  Despite the fact that there was ZERO evidence from clinical trials to back up this claim, the article only contained one short paragraph explaining that Keys' hypothesis was "still questioned by some researchers with conflicting ideas of what causes coronary heart disease."

The second important study done by Ancel Keys was considered to be his masterpiece, The Seven Countries Study.  This study is still, today, considered to be a landmark study because of the pivotal role it played in the acceptance of the diet-heart hypothesis.  Launched in 1956, Keys' followed 16,000 middle-aged men for over a decade and tracked their diets and their heart-disease risk.  The populations he chose came from seven countries:  Italy, Yugoslavia, Greece, Finland, the Netherlands, Japan, and the United States.  The results showed, again, a remarkably clear association, but this time the association was between saturated fat and heart disease.  Keys drew three conclusions from this study:  1. Cholesterol levels predicted heart disease.  2. The amount of saturated fat predicted cholesterol levels and heart disease.  3. Monounsaturated fats protected against heart disease.

Seems pretty clear huh?  Not quite... there are a number of problems with the study.  First and foremost, this is an observational study, and like I've said a million times, you cannot determine any causality from it.  Secondly, Keys chose countries that he knew would fit his hypothesis.  Had he chosen at random, he may have included countries like France or Switzerland that consume high amounts of saturated fat and have very little heart disease.  Third, we know now that middle-aged men are the only population for which total cholesterol numbers can predict heart disease, and the Seven Countries Study only looked at middle-aged men.  Lastly, and perhaps most importantly, Keys didn't look at total mortality, even though what we really want to know is whether or not we'll live longer.  Coronary heart disease accounted for less than a third of deaths.  He said himself in a 1984 follow-up paper, "little attention was given to longevity or total mortality."  Interestingly, if all-cause death had been taken into account, Keys would have found that the American population he studied lived longer than any other population with the exception of the Crete islanders, despite their high cholesterol. 

Even with all of the problems with Ancel Keys' research, his findings on saturated fat and cholesterol would have a profound impact on the public due to a sort-of perfect storm of events that would eventually lead up to the first government dietary recommendations, Senator George McGovern's 1977 Dietary Guidelines for America.  More on that in part 4!

1 comment:

  1. Once again, great post.

    Very interesting that keys was responsible for the "k ration"

    Also, could you imagine going back in time and stopping Keys and his supporter from joining the AHA? Wonder where we would be today. I wonder how different the food pyramid would be, if lowfat products would have ever been created, whether statin drugs would be used...

    that would make an awesome movie! i'm gonna write to hollywood