Keys gave different diets to schizophrenic patients at Minnesota hospital ranging from 9 to 24 percent fat content, and saw that lower fat diets performed a little better in lowering cholesterol. But, the study was performed on only 60 patients, and he included none of the details in his final paper. Using these results, he professed that a perfect curve existed between plaque accumulating on artery walls and fat in the diet. He called it the “diet-heart hypothesis.” Further, he thought that fat must make people fat.
The logic makes sense, but is that only because we’ve heard it for over 60 years? Fat does have 9 calories per gram, versus 4 calories per gram for protein and carbohydrates.
To prove his point – although there was already some data on the subject from Eskimos, the Masai of Africa, and the Navajo Indians – he and his wife traveled to many countries, measuring cholesterol levels of adult males in South Africa, Sardinia, Sweden, Spain, Italy, Finland and Japan. They would visit remote villages, testing subjects including fisherman, farmers, and loggers.
While Keys did write down what he saw some of his early subjects eat, he had no great way to track diets. Further, he did travel to many locations, but his sample sizes were quite small.
Back in Minnesota, he saw that cholesterol would go up after the schizophrenic men ate saturated fat (found in animal fats) and down when they consumed vegetable oils. With this knowledge, he published the “Keys equation,” where he advocated dropping eggs, dairy products, meats and all visible fats to lower the heart disease rate in a population. He told everyone to switch to vegetable fats.
Keys published a paper comparing 6 of the countries he visited, and linked mortality to percent fat calories in the diet. A biostatistics professor from UC-Berkeley thought the results looked fishy, and then compiled data for the 22 countries in which national data was available – the correlation disappeared.
But Keys refuted the other studies, calling the data flawed. Then, he used selected portions the same data set to defend his own study.
The study to end all studies
Keys would standardize data collection in 7 countries that fit his hypothesis well; Italy, Greece, Yugoslavia, Finland, the Netherlands, Japan, and the United States. Greece, Italy, and Yugoslavia were still recovering from WWII. It was called the Seven Countries study, and a 2004 analysis shows that it has been referenced over a million times since it was published.
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