An American doctor flew to Kenya in the early 1960s to prove that a people living on milk, meat and blood would have the worst hearts on earth, and found 400 men without a sign of heart disease between them.
George Mann was a Vanderbilt professor who had helped set up the Framingham study, and he was not a crank. The theory of the day said that saturated fat raised cholesterol and cholesterol furred the arteries, and the Masai of the Rift Valley were the perfect test, because they ate almost nothing else. A warrior lived on milk, several litres of it a day, fresh or soured. He ate meat at feasts and on raids. When a bullock was needed and not to be killed, he opened a vein in its neck, drew off a gourd of blood, and drank that mixed with the milk. Vegetables were for women and the sick. By the arithmetic of the American Heart Association, the Masai should have been dropping on the plain.
Mann put them through the machines. He took blood from hundreds and ran electrocardiograms on 400 young and middle-aged men, and in all of them found no evidence whatsoever of heart disease. Their cholesterol came back at about half the figure of an American of the same age. He put them on a step test and a treadmill and recorded a fitness he could only describe as Olympic standard: men who walked 20 miles a day behind cattle and would run alongside a vehicle for the fun of it.
He went back and did the hard part. In 1972 he published autopsies on 50 Masai, and here is where the honest reader has to sit still, because it is the detail that makes the story. Their aortas showed atherosclerosis, plenty of it, lipid and fibrous change the whole length. And their coronary arteries were wide, far wider than an American's, and in none of the hearts was there a trace of a blockage, a scar or an infarct. They had the plaque and not the disease. The pipe had grown with the load. Whatever killed a Masai, and plenty did, it was not his milk.
Mann came home a heretic and spent the rest of his career saying so in the journals, loudly, and the journals stopped printing him.
The belief he had gone out to confirm is the belief still printed on the tub: that the fat of the animal is what stops a human heart. He took the best instruments of his age to the people who ate more of it than anyone alive, and the instruments said no, and the people were the fittest he had ever measured. The response of his profession was to find other populations.
Four hundred men, half a doctor's expected cholesterol, zero disease, and a blood-and-milk breakfast. The science has had 60 years to answer that and has preferred to change the subject.