Re-evaluation of the Traditional Diet-Heart Hypothesis: Minnesota Coronary Experiment Reanalysis

The Minnesota Coronary Experiment (1968–73) was one of the largest and most rigorous dietary fat intervention trials ever conducted, but its data had never been fully published. This 2016 BMJ paper analyzed recovered data from 9,423 institutionalized participants randomized to a diet replacing saturated fat with linoleic acid (corn oil-enriched margarine and vegetable oil) versus a control diet.

The linoleic acid intervention successfully reduced serum cholesterol by approximately 14% — confirming its lipid-lowering effect. However, this cholesterol reduction was not associated with mortality benefit. In fact, in those participants who achieved the greatest cholesterol reduction, mortality risk was nominally higher. Neither all-cause mortality nor coronary heart disease mortality improved with the linoleic acid intervention.

The finding is methodologically important for the diet-heart debate. It distinguishes between two hypotheses: (1) that saturated fat raises LDL-C, and (2) that replacing saturated fat with polyunsaturated fat (linoleic acid specifically) reduces cardiovascular mortality. The Minnesota data confirm the first but challenge the second — at least for n-6 linoleic acid specifically. It does not challenge the case for replacing saturated fat with long-chain omega-3 fatty acids or other evidence-based dietary patterns.

The recovered-data design, the institutionalized population, and the historical limitations of the original trial design all constrain interpretation. But this remains one of the best natural experiments testing the diet-heart hypothesis directly.

We rate the evidence strong for the strength of the experimental design. A recovered-data reanalysis of a rigorous RCT showing that LDL-C reduction via linoleic acid did not reduce cardiovascular mortality — complicating simple lipid-lowering interpretations of the diet-heart hypothesis.