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

Abstract

Objective To examine the traditional diet-heart hypothesis through recovery and analysis of previously unpublished data from the Minnesota Coronary Experiment (MCE) and to put findings in the context of existing diet-heart randomized controlled trials through a systematic review and meta-analysis.Design The MCE (1968-73) is a double blind randomized controlled trial designed to test whether replacement of saturated fat with vegetable oil rich in linoleic acid reduces coronary heart disease and death by lowering serum cholesterol. Recovered MCE unpublished documents and raw data were analyzed according to hypotheses prespecified by original investigators. Further, a systematic review and meta-analyses of randomized controlled trials that lowered serum cholesterol by providing vegetable oil rich in linoleic acid in place of saturated fat without confounding by concomitant interventions was conducted.Setting One nursing home and six state mental hospitals in Minnesota, United States.Participants Unpublished documents with completed analyses for the randomized cohort of 9423 women and men aged 20-97; longitudinal data on serum cholesterol for the 2355 participants exposed to the study diets for a year or more; 149 completed autopsy files.Interventions Serum 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.Main outcome measures Death from all causes; association between changes in serum cholesterol and death; and coronary atherosclerosis and myocardial infarcts detected at autopsy.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).Conclusions Available evidence from randomized controlled trials shows that replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes. Findings from the Minnesota Coronary Experiment add to growing evidence that incomplete publication has contributed to overestimation of the benefits of replacing saturated fat with vegetable oils...

Dairy fat and risk of cardiovascular disease in 3 cohorts of US adults

“…Future studies regarding different food sources of vegetable fat or PUFA are warranted. Ramsden et al (42) observed that the replacement of saturated fat with vegetable oils that were rich in linoleic acid significantly reduced serum cholesterol by 13.8% (compared with a 1% reduction in the control), but the reduction in serum cholesterol did not lead to an expected reduction in CVD mortality. However, the study was hampered by a short duration of intervention (average: 1 y), extremely high rates of dropouts, and potential confounding by the trans-fat content in the vegetable oils.…”

Re: Kjøtt sett i relasjon til evolusjonen

“…I motsetning til forskning om kjøtt finnes det mye forskning som konkluderer med at belgvekster kan gi flere helsefordeler (4,5), og at mer plantebaserte kosttyper er sunnere enn et vanlig vestlig, animalskbasert kosthold (6,7).…”

“…Retterstøl mener at dietteksperimentene beviser kolesterolhypotesen, men han nevner bare de to som resulterte i en beskjeden forbedring og ingen av de mange mislykkede eksperimentene. I to av disse økte faktisk dødeligheten med statistisk sikkerhet (4,5). En metaanalyse av kosteksperimentene har dessuten trukket i tvil effekten av å erstatte mettet fett med flerumettet fett i sekundaerprofylakse av koronar hjertesykdom (6).…”

Saturated fat –a never ending story?

“…Without access to a real placebo, the double-blind design fails. The closest approach to a double-blind design on hard CVD endpoints in nutritional science is probably the Finnish Mental Hospital studies [17,18] and the Minnesota Coronary Experiment [1]. In these studies, hospitals were selected or randomized to serve foods low in SFA or no dietary change, which is far from a conventional placebo-RCT design.…”

“…Saturated fatty acids (SFA) do not increase the risk of cardiovascular disease (CVD), two recently published analyses of randomized controlled trials (RCTs) concluded [1,2]. Replacing SFA with linoleic acid increased CVD risk in one trial [2].…”