How saturated fat was demonised

Photo by Maayan Nemanov on Unsplash

The history is revealing

Dr Ancel Keys (1904–2004) was an American epidemiologist who was interested in the effects of diet on health. During World War II, Keys developed the K-ration given to soldiers in the field (the ‘K’ was no coincidence), and studied starvation and recovery in conscientious objectors (inhuman experiments without the nuisance of ethics committees). He was described as ‘confident’.


The AHA recommends that people at risk of heart disease limit total fat intake to 30% of calories (10% saturated; 20% unsaturated). To keep some perspective, Keys himself only recommended limiting carving meats (roasts etc) to 3 times a week.


The National Institutes of Health sets up a Diet Review Panel of experts in epidemiology, statistics, nutrition and clinical medicine to review the evidence for the hypothesis that saturated fat increases the risk of heart disease. They find that the available evidence does not support the hypothesis and, furthermore, express concerns that reducing fat intake could have adverse consequences.


A Select Committee on Nutrition and Human Needs ponders the recommendation for dietary fat to be included in the upcoming ‘US Dietary Goals’. This highly-contentious committee, comprising mostly non-experts in the field and written by a vegan junior staffer without a scientific background, recommends extending the AHA guidelines (until then for people at risk of heart disease) to the entire American adult public.


A series of well-controlled saturated fat studies are published that consistently find no link to heart disease.


The results from the Coronary Primary Prevention Trial are published, confirming the Framingham study by showing a weak association between blood levels of cholesterol and heart disease. This triggers a renewed public campaign, another cover on Time magazine, and the extension of the AHA guidelines to every American over the age of 2 years (regardless of anything else).


The US Surgeon General’s Office commissions what it hopes will be the definitive report linking saturated fat to cholesterol and heart disease. The task is to compile the science and get it reviewed by an expert committee who would issue a proclamation. The committee is tasked with supporting the hypothesis that saturated fat increases the risk of heart disease (it is not required to compare the scientific data for or against the hypothesis). It takes longer than expected (see 1999).


A disturbing turn of events. Data starts to appear showing that low levels of dietary saturated fat might be associated with other mortalities such as cancer and respiratory illness. A troubling finding was an increased likelihood of death by accident and trauma — the brain might have gone into a high-risk survival mode. The fears that dietary advice could do harm were realised — not surprisingly, fat had a bigger role to play in our biology than just the heart. The authorities do nothing — they ignore the most fundamental principle in medicine — do no harm.


It has now been eleven years since the US Surgeon General’s Office committee was convened (in 1988). They give up. In the face of the complexity of the task and the simple fact that the science was not supporting the hypothesis, the committee quietly admits defeat and disbands without fanfare.


Large meta-analyses of prospective (stage 3) studies appear in the following decade. The conclusion remains the same — despite decades of research effort and who knows how many hundreds of millions in precious research dollars, it is still not possible to definitively show that saturated fat has any significant part to play in heart disease.


Our diet has been experimented on at a national level with an hypothesis that started out as a campaign by a relentlessly ambitious individual, that went on to become lore, that didn’t and doesn’t have scientific backing, and that is likely to be harmful to our health.

Further reading:

The Gary Taubes article was highly influential when published in 2001: The soft science of dietary fat



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Science of cooking, eating and health. Retired neuroscientist.