What we know about fat may be wrong.
When Dr Keys first published his theories, alleging that saturated fats were uniquely harmful, they were controversial. This controversy remains strong today as the debate on the roles of fat and sugar in relation to cardiovascular disease (CVD) associated with atheroma (the fatty material that forms plaques in arteries) goes on.
This article reflects upon two main subjects: understanding the complexity of chronic diseases as the antithesis of acute infectious diseases; and the principle of falsifiability applied to atheroma theories and the practical consequences this entails.
After World War II, the work of Dr Keys played a fundamental role in the debate around fats. How?
Because it claimed to demonstrate a link between saturated fats consumption and atheroma: “Many factors are probably involved in the atherosclerotic development and in the clinical appearance of coronary heart disease, but there is no longer any doubt that one central item is the concentration, over time, of cholesterol and related lipids and lipoproteins in the blood serum. No other etiological (sic) influence of comparable importance is as yet identified.” (A. Keys, American Journal of Public Health, Nov 1953, vol 43, 1399-1407.)
Today, in reality, scientists see tobacco, diabetes and hypertension to be much more powerful risk factors. We condemn researchers who, for over 40 years, have not been keen to verify the data and the conclusions it suggested.
Epidemiology in modern history
Epidemiologic observations have drawn the attention of scientists for a long time on the link between dietary change and cardiovascular diseases. Examples of populations with low CVD prevalence or populations where CVD are the first cause of mortality have led epidemiologists to do research on food.
This is what we called the Diet-Heart Hypothesis. But it is so incredibly complex that even till today, we have yet to come up with a definitive answer. Simple hypo- theses (i.e. single-factor cause) and invalid experimental models have produced abundant literature, of which little is actually helpful.
We can, however, wonder about the recent dietary changes brought by the recent industrial transition. In the West, those changes can be qualified with three factors:
• Abundance of calories
• Abundance of carbohydrates
• Abundance of processed foods
Further to these, we should not forget about calorie expenditure. In industrialised countries, we have shifted to a sedentary lifestyle (at work, in public transportation or for personal activities).
Dr Keys supported his hypothesis with charisma.
How is that possible?
He and his team set out to study the dietary characteristics and lifestyles of different populations worldwide and compare the prevalence of coronary diseases. It was a rather large study at the time and needed significant funding.
This study addressed the issue of the heart attack epidemic that was hitting the United States and other developed countries at the time. He quickly focused on diet-related risk factors, mostly because they were easier to measure, particularly through blood levels.
Among macronutrients, Dr Keys had already explored fat and the indirect measure of blood lipids via blood cholesterol.
The study would be published in a book in 1980 (Seven Countries. A multivariate analysis of death and coronary heart disease).
In the meantime, Dr Keys got more famous, was interviewed often, and in January 1961, was on the cover of Time Magazine.
Dr Keys described a link in the studied cohorts between the percentage of saturated fats in the diet and the death rate by coronary events. The correlation was dependent on the number of countries studied, but it was significant in the cohorts he chose.
As there was a correlation between total blood cholesterol and the same events, and as Dr Keys highlighted that saturated fats (especially palmitic acid as it is the most common) increased blood cholesterol, a conclusion appeared.
He stated that saturated fats, including palmitic acid, were link-ed to coronary atheroma. Others have then bridged the gap, saying they cause coronary diseases.
Obviously, all of this was not true. Inaccuracies and biases made his observations invalid.
Even Dr Keys ended up publishing more balanced conclusions than others: “Our 10 year finding, and concordance with other studies, make it clear that the big three risk factors for coronary heart disease now established are age, blood pressure, and serum cholesterol. The findings about cigarette smoking as a risk factor indicate that here, too, relationships are not as simple as first supposed.” (Seven Countries, page 341).
He later became an advocate of the Mediterranean diet and kept studying it for a while. In 1975, he published How to Eat Well and Stay Well the Mediterranean Way.
Consequences still felt today
Dietary guidelines from experts and governments have been largely based on Dr Keys’ work.
To lower our intake in cholesterol and saturated fats, populations have massively consumed food products in which fats have been replaced with carbohydrates, and saturated fats with vegetable oils rich in omega-6.
This did not change the prevalence of atheroma-related diseases. New research even shows these changes may be linked to the obesity epidemic and type 2 diabetes.
Palm oil for one, which has a good balance between saturated and unsaturated fats, constitutes a healthy alternative – but it has been unjustly maligned for containing saturated fats.
There have been economic consequences too. This is linked to the food industry’s ability to quickly find a new market opportunity with low-fat food products. It has, as always, been shown to be very innovative in that regard.
Its lobby was powerful and the “low-fat” concept developed globally even though it is not possible as of yet to show it has any positive impact of cardiovascular health.
In the 40 years between Dr Keys’ work and the shadow cast upon it, many scientific articles have been published to try and explain the anomalies observed in real populations.
None ever questioned what had become a dogma. The different paradoxes, including the famous French Paradox, have only started to shake the foundation of his hypothesis.
Who bears the responsibility?
Surely, Dr Keys cannot be held responsible for how his data was used.
But his vision clearly influenced medicine for generations and overstated the importance of saturated fats and cholesterol in cardiovascular risk.
A summary of the Seven Countries Study on the University of Minnesota, US (where the study was coordinated), website, had this to say: “The main implications of the Seven Countries Study are that the mass burden and epidemic of atherosclerotic diseases has cultural origins, is preventable, can change rapidly, and is strongly influenced by the fatty composition of the habitual diet.
“The study implies the universal susceptibility of humans to CVD, but that the frequency of susceptible phenotypes is greatly reduced in favourable environments. It suggests there may be other and important protective elements in the diet and lifestyles of Crete and Japan.”
The only concession made to Dr Keys’ theories is the confirmation of a strong influence of the composition of lipids in the diet, but the words “saturated fats” are no longer used.
The Journal of the American College of Cardiology recently reminded physicians:“Atherosclerosis is a multifactorial disease and requires a multifactorial approach with smoking cessation, dietary modification and weight management, regular physical activity, attention to psychosocial risk factors, and pharmacological therapy of lipid and nonlipid risk factors.
“Comprehensive risk factor control is associated with improved prognosis, and our challenge is to develop care models that will allow us to achieve such control.”
We need to keep in mind that tobacco, type 2 diabetes and hypertension are, in that order, more powerful atheroma risk factors than LDL particles. There is no interest in dietary cholesterol in preventing CVD.
Saturated fats, like monounsaturated fats, and like carbohydrates, increase the amount of LDL particles when in calorie excess and promotes atheroma if other risk factors are present, and if phenotype is susceptible.
This is the reason why we cannot predict among high-LDL patients those who will have a cardiovascular, cerebral or peripheral event, other than watching the three aforementioned powerful risk factors, or having proper atheroma plaques exams.
In summary, Dr Keys was wrong, and his mistake has been compounded over the decades. It is time now to end the crusade against saturated fats.
Dr Guy-André Pelouze is a French cardiothoracic surgeon, and a founder of the French think tank and research group Institut de Recherche Clinique (Institute of Clinical Research). Dr Pelouze is a widely quoted writer and commentator on health and nutrition in France. This article contains extracts from the scientific paper, ‘Ancel Keys: Science is not believing’.
http://www.star2.com/health/wellness/2016/04/24/what-we-know-about-fat-may-be-wrong/