Heart disease, which had been a relative rarity in the 1920s, was now felling middle-aged men at a frightening rate, and Americans were casting around for cause and cure. Ancel Keys provided an answer: the “diet-heart hypothesis” (for simplicity’s sake, I am calling it the “fat hypothesis”). This is the idea, now familiar, that an excess of saturated fats in the diet, from red meat, cheese, butter, and eggs, raises cholesterol, which congeals on the inside of coronary arteries, causing them to harden and narrow, until the flow of blood is staunched and the heart seizes up.
Ancel Keys was brilliant, charismatic, and combative. A friendly colleague at the University of Minnesota described him as, “direct to the point of bluntness, critical to the point of skewering”; others were less charitable. He exuded conviction at a time when confidence was most welcome. The president, the physician and the scientist formed a reassuring chain of male authority, and the notion that fatty foods were unhealthy started to take hold with doctors, and the public. (Eisenhower himself cut saturated fats and cholesterol from his diet altogether, right up until his death, in 1969, from heart disease.)
Many scientists, especially British ones, remained sceptical. The most prominent doubter was John Yudkin, then the UK’s leading nutritionist. When Yudkin looked at the data on heart disease, he was struck by its correlation with the consumption of sugar, not fat. He carried out a series of laboratory experiments on animals and humans, and observed, as others had before him, that sugar is processed in the liver, where it turns to fat, before entering the bloodstream.
