Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73). Ramsden (2016)

Ramsden CE, Zamora D, Majchrzak-Hong S, Faurot KR, Broste SK, Frantz RP, Davis JM, Ringel A, Suchindran CM,Hibbeln JR. (2016)

Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73).

BMJ. 2016 Apr 12;353:i1246.
DOI: 10.1136/bmj.i1246.
pubmed

Summary:Randomized double blind clinical trial of 9423 women and men aged 20-97.  The intervention was a cholesterol lowering diet that replaced saturated fat with linoleic acid (from corn oil and corn oil polyunsaturated margarine). Control diet was high in saturated fat from animal fats, common margarines, and shortenings.

Results: The intervention group had significant reduction in serum cholesterol compared with controls (mean change from baseline -13.8%v-1.0%; P<0.001). Kaplan Meier graphs showed no mortality benefit for the intervention group in the full randomized cohort or for any prespecified subgroup. There was a 22% higher risk of death for each 30 mg/dL (0.78 mmol/L) reduction in serum cholesterol in covariate adjusted Cox regression models (hazard ratio 1.22, 95% confidence interval 1.14 to 1.32; P<0.001). There was no evidence of benefit in the intervention group for coronary atherosclerosis or myocardial infarcts. Systematic review identified five randomized controlled trials for inclusion (n=10,808). In meta-analyses, these cholesterol lowering interventions showed no evidence of benefit on mortality from coronary heart disease (1.13, 0.83 to 1.54) or all cause mortality (1.07, 0.90 to 1.27).

We reckon: This study was conducted by one of the key proponents of the diet heart hypothesis that has informed our dietary guidelines since the 70s, Ancel Keys.  This study showed that the advice to replace dietary Saturated fats with Polyunsaturated fats did indeed lower serum cholesterol, but that did not decrease the risks of Cardiovascular disease or all cause Mortality.  In fact this re-evaluation has been able to show that for every 30 mg/dL reduction in serum cholesterol there was a 22% higher risk of death.

The study results were only published 18 years later in 1989 in minor journals without statistics and effectively buried until this 2016 re-evaluation uncovered them.  For that entire time since Ancel Keys joined the Nutrition committee of the AHA in 1961, their official advice has been to replace Saturated fat with Polyunsaturated fat to lower LDL cholesterol and reduce the risk of Heart disease.  This study and the Sydney Diet Heart study ( Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis.-Ramsden(2013)) showed in 1973 that advice to be not only incorrect, but deadly.

In 2016, this remains the advice of the American Heart Association.