Heart disease is one of the main causes of death in the western world. It is responsible for around 20% of the deaths in the USA (https://www.cdc.gov/nchs/fastats/leading-causes-of-death.htm), whilst in Europe circulatory diseases cause slightly more than 30% of deaths. Given its significance and novelty, only becoming a prevalent driver of death by the 1950s, it is no wonder that much thought has been given to the cause and potential treatment of heart disease.
One possible explanation of heart diseases is the diet-heart hypothesis, first proposed by Ancel Keys in the 1950s. The hypothesis suggests that a high consumption of saturated fats and cholesterol is the main driver of heart disease. Supposedly, it leads to increased serum cholesterol which then leads to heart disease. According to this hypothesis, replacing saturated fats with unsaturated fats high in linoleic acid should decrease serum cholesterol and reduce the risk of heart disease.
The Minnesota Coronary Experiment (subsequently MCE) was a study conducted between 1968 and 1973 which intended to ascertain the validity of this hypothesis. The study showed that a diet replacing saturated fats with vegetable oils rich in linoleic acid significantly reduced serum cholesterol when compared to a control diet much higher in saturated fats.
Despite the MCE seemingly supporting the diet-heart hypothesis, some of the key data from the study was never published, significantly skewing the results. Thus, in the 2016 paper entitled 'Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73)', Ramsden et al. set out to recover unpublished data from the MCE and analyse it to provide a more thorough assessment.
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Much like the MCE they found that replacing saturated fats with unsaturated fats high in linoleic acid did significantly reduce serum cholesterol. However, when looking at both coronary and aortic atherosclerosis there was no significant difference between the group that had replaced saturated fats with linoleic acid and the group that had maintained a diet relatively high in saturated fats.
This directly contradicts the projection of the diet-heart hypothesis which would suggest that the lower serum cholesterol should reduce atherosclerosis. Furthermore, instead of decreasing the risk of death, as would be expected according to the diet-heart hypothesis, a reduction in serum cholesterol was correlated with an increased risk of death.
When moving beyond the MCE and examining other, non-randomised studies, Ramsden et al. found conflicting evidence with some studies supporting the diet-heart hypothesis and other others finding no association between linoleic acid consumption and risk of heart disease.
Overall, the findings by Ramsden et al. challenge the prevailing view that saturated fats are the main drivers of the rapid rise in heart disease in modern times and put into question the long-dominant diet-heart hypothesis.
References
- Ramsden, C. E., Zamora, D., Majchrzak-Hong, S., Faurot, K. R., Broste, S. K., Frantz, R. P., Davis, J. M., Ringel, A., Suchindran, C. M., & Hibbeln, J. R. (2016). Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73). BMJ (Clinical research ed.), 353, i1246. 10.1136/bmj.i1246.
