India ran the most important cardiovascular study of the 20th century by accident, and then immediately forgot about it. In 1967, Dr. S.L. Malhotra published a study in the British Heart Journal examining heart disease rates among 1.5 million Indian railway employees. The population was extraordinarily useful for research purposes: same employer, same healthcare access, comparable income and working conditions, spread across the entire country. The only meaningful variable was geography. Which meant diet. North Indian railway workers: Punjab, Rajasthan, UP, ate a diet built around ghee and dairy fat. They consumed up to 19 times more fat than their southern counterparts. The fat was primarily saturated: clarified butter, milk fat, the short-chain saturated fatty acids that Ancel Keys had recently been telling the Western world were arterial death. South Indian railway workers ate a diet based on rice, sambar, and seed oils: groundnut oil and sesame oil, primarily. They ate considerably less fat overall. By the standards of dietary advice being formulated in the 1960s, they should have been the healthy ones. Heart disease mortality in South India: 135 per 100,000. Heart disease mortality in North India: 20 per 100,000. Seven times higher in the population eating seed oils. Among railway sweepers specifically, the lowest-paid, most physically active workers, the gap was even wider. Heart disease was fifteen times more common in the South Indian sweeper population than in the North Indian sweeper population. Malhotra controlled for everything he could reach: smoking, where Northerners actually smoked more. Activity levels, where the relationship was inconsistent. Socioeconomic status, where executives died more often than sweepers regardless of region. He found no variable that explained the gap except the type of fat in the diet. He published the data. In a peer-reviewed journal. In 1967. The study was cited periodically, acknowledged as methodologically interesting, and then set aside. The decade in which Malhotra published was the decade in which Ancel Keys's fat hypothesis was being converted into policy. The American Heart Association was issuing guidance recommending polyunsaturated vegetable oils as replacements for saturated animal fats. The food industry was producing seed oils at industrial scale. The infrastructure of seed oil promotion was being built, expensively and with great institutional momentum. A study showing that populations eating animal fat had a fraction of the heart disease of populations eating seed oils was not, in that context, a study that anyone particularly wanted to follow up. Nobody followed up. Almost sixty years later, the finding stands unrefuted in the literature. It is not in the dietary guidelines.