In this 2023 review, Nina Teicholz traces how the diet-heart hypothesis—the idea that saturated fat causes heart disease—became widely accepted despite weak early evidence. First proposed in the 1950s based largely on observational data, the theory gained momentum through influential figures and institutions like the American Heart Association and was eventually built into global dietary guidelines.

Large randomized trials in the 1960s and 1970s failed to show that replacing saturated fats with vegetable oils reduced heart attacks or mortality, despite lowering cholesterol. Some of these findings were delayed or never published, and contradictory evidence from studies like Framingham was largely overlooked. More recent re-analyses and over 20 review papers have since found no clear link between saturated fat and cardiovascular outcomes, challenging the original hypothesis.

Nina highlights how bias, conflicts of interest, and flawed review processes can shape scientific consensus—and how long it can take for policy to catch up once that consensus begins to unravel.