The Seven Countries Study (Ancel Keys, 1958)

Ancel Keys' Seven Countries Study fundamentally reshaped global nutritional policy for five decades by linking dietary saturated fat to heart disease. The study examined 12,763 middle-aged men across seven nations, but critics argue Keys cherry-picked data, excluding countries like France and West Germany, where high fat intake correlated with low heart disease rates. Subsequent re-analyses found that when all available data were included, the fat-heart connection weakened by nearly 40%. This selective reporting makes it more methodologically suspect than the WHI HRT study, which at least underwent rigorous re-audits. The controversy still divides experts today.