Malcolm Kendrick is a Scottish doctor and has been a general practitioner for over 25 years. He has also worked with the European Society of Cardiology.
The letter can be accessed at: http://www.thincs.org/discuss.cavemen.htm
Dear all, Re: The seven countries study, I included a little section on the Seven Countries Study in my book. Sorry if it is bit long, but I though it may amuse you all.
The Seven Countries Study
But what of the supportive data? Surely it must be based on something? Of course it is, and what it is mainly based on is Ancel Keys and his seven countries study - possibly the single most important piece of research in the development of the saturated fat hypothesis. This study ‘proved’ that the more saturated fat consumed in a country, the greater the rate of coronary heart disease (CHD). Or did it?
If you chose, in the mid-nineteen fifties, to study the seven countries that Ancel Keys looked at.
Then you could find an almost perfect correlation between saturated fat intake and CHD.
However, if Ancel Keys had chosen to study:
Then he would have discovered the exact opposite. Namely, the more cholesterol/saturated fat consumed, the less CHD. Indeed, if you were to have chosen any other seven countries in the world, apart from the ones Ancel Keys chose, you would get a different set of results. How Ancel Keys came to choose his seven countries will probably never be known – unless he makes a deathbed confession.
As a piece of scientific research, the possibility that Ancel Keys introduced bias is so great that – were this study to be proposed today – it would be thrown out by any decent research committee. (Imagined conversation)
Ancel Keys: I would like to carry out research into the correlation between heart disease and saturated fat/cholesterol consumption in different countries.
Member of research council: ‘Very good – how will you select the countries?’
Ancel Keys: I have already selected them.
Member of research council: How did you make the selection?
Ancel Keys: I just thought they seemed like good countries.
Chairman of research council: Jolly good, carry on!
Ancel Keys: Thanks.
I can just imagine what would happen if I suggested a study on another seven countries, specifically designed to disprove the diet-heart hypothesis, having first chosen my seven countries, for my own reasons, I would be laughed out of court, and so I should be.
If you think that I am joking about this, then read on, because I am deadly serious. Recently, Henry Blackburn, a doctor who worked closely with Ancel Keys, and became a personal friend, wrote a history of the Seven Countries Study. What does Dr Blackburn have to say about the lack of randomisation?
‘The study has been criticized for the method in which populations were selected for the study, and the way that the population (ecologic) correlations, with limited numbers of units, were carried out. These days, the configuration of populations for such internal and international comparisons is strengthened by the random selection of greater numbers of units. But the Seven Countries Study was state-of-the-art for its time, and the concept ahead of its time.’ Henry Blackburn M.D. Division of Epidemiology. University of Minnesota
So it’s all right. Everyone admits that there was no randomisation in the seven countries study, but this doesn’t matter because it was ‘state-of-the-art for its time.’ No it wasn’t, people were carrying out randomised clinical trials at the turn of the twentieth century, and the first population study known of was done in 1666, in London, to discover the cause of an outbreak of cholera, a mere two hundred and ninety years before. Ahead of its time?
More revealing perhaps is a short tale about the motivation for Ancel Keys and his Seven Countries Study.
‘In 1954, the fledgling World Health Organization called its first Expert Committee on the Pathogenesis of Atherosclerosis to consider the burgeoning epidemic of coronary disease and heart attacks. Several medical leaders of the time were assembled in Geneva: Paul Dudley White of Boston, Gunnar Björk of Stockholm, Noboru Kimura of Japan, George Pickering of Oxford, Ancel Keys of Minnesota, and others. As reported by Pickering, the discussion was lively, tending to tangents and tirades.
Ancel Keys was in good form -- outspoken, quick, typically blunt. When, at this critical conference, he posed with such assurance his dietary hypothesis of coronary heart disease, he was ill-prepared for the indignant reaction of some.
George Pickering, recently named Knight of the Realm by Queen Elizabeth, interrupted Keys' peroration. He put it something along these lines: 'Tell us, Professor Keys, if you would be so kind, what is the single best piece of evidence you can cite in support of your thesis about diet and coronary heart disease?'
Keys, ordinarily quick on the draw, was taken aback. Rarely, of course, is there ever a 'single best piece of evidence' supporting any theory. Theory is developed from a body of evidence and varied sources. This is particularly true in regard to the many facets of lifestyle that relate to disease. It is the totality and congruity of evidence that leads to a theory -- and to inference of causation.
Keys fell headlong into the trap. He proceeded to cite a piece of evidence. Sir George and the assembled peers were easily able to diminish this single piece of evidence, and did so. And by then it was too late to recover -- for Keys to summon the total evidence in a constructive, convincing argument.
My theory is that Keys was so stung by this event that he left the Geneva meeting intent on gathering the definitive evidence to establish or refute the diet-Heart Theory. Out of this singular, moving, personal experience -- so my theory goes -- came the challenge, the motivation, and eventually, the implementation of the Seven Countries Study.’
As Dr Blackburn reveals, point one: Ancel Keys was already certain that a high animal fat diet was the cause of heart disease – before he organised the seven countries study. More worryingly, Ancel Keys was so stung by an attack on him by Sir George Pickering that he vowed to go out and prove him wrong! Now that’s a good motivation for an objective, scientific clinical trial. Any chance that a man aiming for revenge could be tempted towards bias?
Frankly, this whole trial should be consigned to the dustbin. The results themselves cannot be argued with. They are what they are. But in reality all that this study proved was that if you carefully choose seven countries where you already know the rates of CHD, and the level of saturated fat consumption, then you can demonstrate a close association between saturated fat consumption and CHD. That association, in those countries, has now broken down, and it never clearly existed for any other seven countries in the world.
Finally, there was no association between CHD and saturated fat intake within the countries he chose to study. In Greece, the level of saturated fat consumption was virtually the same in all regions studied, yet the rate of CHD varied by a factor of seven. If it were not for the risk of libel, I would state what I really think of the seven countries study.