Bold policies have been based on fragile science, and the long term results may be terrible, Richard Smith says — speaking of diets:
By far the best of the books I’ve read to write this article is Nina Teicholz’s The Big Fat Surprise, whose subtitle is “Why butter, meat, and cheese belong in a healthy diet.”The title, the subtitle, and the cover of the book are all demeaning, but the forensic demolition of the hypothesis that saturated fat is the cause of cardiovascular disease is impressive. Indeed, the book is deeply disturbing in showing how overenthusiastic scientists, poor science, massive conflicts of interest, and politically driven policy makers can make deeply damaging mistakes. Over 40 years I’ve come to recognise what I might have known from the beginning that science is a human activity with the error, self deception, grandiosity, bias, self interest, cruelty, fraud, and theft that is inherent in all human activities (together with some saintliness), but this book shook me.
Teicholz begins her examination by pointing out that the Inuit, the Masai, and the Samburu people of Uganda all originally ate diets that were 60-80% fat and yet were not obese and did not have hypertension or heart disease.
The hypothesis that saturated fat is the main dietary cause of cardiovascular disease is strongly associated with one man, Ancel Benjamin Keys, a biologist at the University of Minnesota. He was clearly a remarkable man and a great salesman, described by his colleague Henry Blackburn (whom I’ve had the privilege to meet) as “possessing a very quick, bright intelligence” but also “direct to the point of bluntness, and critical to the point of skewering.”
Keys launched his “diet-heart hypothesis” at a meeting in New York in 1952, when the United States was at the peak of its epidemic of heart disease, with his study showing a close correlation between deaths from heart disease and proportion of fat in the diet in men in six countries (Japan, Italy, England and Wales, Australia, Canada, and the United States). Keys studied few men and did not have a reliable way of measuring diets, and in the case of the Japanese and Italians he studied them soon after the second world war, when there were food shortages. Keys could have gathered data from many more countries and people (women as well as men) and used more careful methods, but, suggests Teicholz, he found what he wanted to find. A subsequent study by other researchers of 22 countries found little correlation between death rates from heart disease and fat consumption, and these authors suggested that there could be other causes, including tobacco and sugar consumption.
At a World Health Organization meeting in 1955 Keys’s hypothesis was met with great criticism, but in response he designed the highly influential Seven Countries Study, which was published in 1970 and showed a strong correlation between saturated fat (Keys had moved on from fat to saturated fat) and deaths from heart disease. Keys did not select countries (such as France, Germany, or Switzerland) where the correlation did not seem so neat, and in Crete and Corfu he studied only nine men. Critics pointed out that although there was a correlation between countries, there was no correlation within countries and nor was there a correlation with total mortality. Furthermore, although the study had 12?770 participants, the food they ate was evaluated in only 3.9%, and some of the studies in Greece were during Lent, when the Greek Orthodox Church proscribes the eating of animal products. A follow-up study by Keys published in 1984 showed that variation in saturated fat consumption could not explain variation in heart disease mortality.
An analysis of the data from the Seven Countries Study in 1999 showed a higher correlation of deaths from heart disease with sugar products and pastries than with animal products. John Yudkin from London had since the late 1950s proposed that sugar might be more important than fat in causing heart disease, but Keys dismissed his hypothesis as a “mountain of nonsense” and a “discredited tune.” Many scientists were sceptical about the saturated fat hypothesis, but as the conviction that the hypothesis was true gripped the leading scientific bodies, policy makers, and the media in the US these critics were steadily silenced, not least through difficulty getting funding to challenge the hypothesis and test other hypotheses.