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

BMJ 2016; 353 doi: https://doi.org/10.1136/bmj.i1246 (Published 12 April 2016) Cite this as: BMJ 2016;353:i1246

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

This paper by Ramsden et al. adds important sub-group analyses to the original publication of the study findings, in 1989, by study director Ivan Frantz, in Arteriosclerosis (1) Frantz et al reported "no difference between the treatment and control groups were observed for cardiovascular events, cardiovascular mortality, or total mortality," Yet the researchers did not publish these findings until 16 years after their study concluded and when asked by science journalist Gary Taubes about the delay, Frantz replied that they were "disappointed" with how the study came out. (2)

This is an extraordinary example of selection bias, by the authors themselves against their own results. Frantz was a strong supporter of the diet-heart hypothesis, and evidently he could not understand his study's null results. Yet Frantz was not alone. As Ramsden et al. report. in their systematic review (also part of this article), there have been other clinical trials, on 10,808 subjects, which, taken together, show "no indication of benefit on coronary heart disease or all cause mortality," And these results have also been largely ignored by nutrition experts.

Over the past 5 years, quite a few researchers have gone back to review both the trial and observational data on saturated fats. Indeed, there are now more than a dozen meta-analyses and systematic reviews of the data that challenge the link between saturated fats and heart disease. (3) A number of researchers and journalists (myself included) have written about the reality that the diet-heart hypothesis (replacing saturated fats with polyunsaturated vegetable oils) was never supported by the evidence. Yet this reconsideration of the data on saturated fats has not yet been fully considered by our health authorities (4), which still recommend limiting saturated fat to less than 10% of calories.

One other interesting note about the Minnesota Coronary Survey: the control group ate more than 18% of calories as saturated fat, without cardiovascular harm. This proportion of saturated fat is consistent with other similar trials. Thus, when researchers ask whether there is an upper limit on saturated fat intake, or question whether we know if higher intakes of these fat are safe, this trial provides such data and suggests that higher intakes are ,indeed, safe.

Nina Teicholz
Science journalist and Author, The Big Fat Surprise

(1) http://www.ncbi.nlm.nih.gov/pubmed/2643423
(2) Taubes, G. iGood Calories, Bad Calories, 2007,
(3) http://www.nutrition-coalition.org/saturated-fats-do-they-cause-heart-di...
(4) Teicholz, N., The BMJ, 2015.

Competing interests: No competing interests

13 April 2016
Nina Teicholz
science journalist
New York, NY