Those who are younger than 40 years old probably grew up hearing that saturated fat is “bad” and polyunsaturated fat is “good”, but where did we get this idea and is it true?
The process of what I call the “vilification of fat” began when researcher Ancel Keys presented a graph at a talk at Mount Sinai Hospital in New York in January 1953 and later published it in a research paper titled Atherosclerosis: a problem in newer public health . It was said to show the relationship between ‘fat calories as a percentage of total fat” and the number of ‘deaths from degenerative heart disease per 100,000 people’ for men between the ages of 45-49 and 55-59. The linear relationship of these data points from the Six Country Study (Japan, Italy, England & Wales, Australia, Canada and the USA) suggested that there was a strong relationship between the amount of fat calories as a percentage of dietary intake and deaths from degenerative heart disease for men aged 55-59. At the time of publication of the Six Country Study, Keys said that it was possible to only get complete data from those 6 countries  at the time. He concluded;
“Whether or not cholesterol etc. are involved, it must be concluded that dietary fat somehow is associated with cardiac diseases mortality, at least in middle age .
In Key’s mind, the total amount of dietary fat was “somehow associated” with cardiac death in middle aged men, but he expressed doubt whether or not cholesterol was involved.
In 1957, Yerushalamy and Hilleboe  published data from 22 countries which showed there was no linear relationship between ‘fat calories as a percentage of total fat” and the number of ‘deaths from degenerative heart disease per 100,000 people’.
Keys went onto conduct what became known as the Seven Country Study which collected data on almost 13,000 men aged 40-59 from the USA, Finland, the Netherlands, Yugoslavia, Greece and Japan. Findings were only published in 1970 in the journal Circulation in several papers from separate countries . Keys no longer believed that total fat was associated with heart disease but that saturated fat was the villain. Keys concluded that the average consumption of animal foods (with the exception of fish) was positively associated with 25-year heart disease death rates and that the average intake of saturated fat was strongly related to 10 and 25-year coronary heart disease death rates.
What solidified this association was that the 1970 publication on the Seven Country Study contained Keys’ 1953 graph from the Six Country Study (above) . Even though it indicated a linear relationship between total fat intake and degenerative heart disease it became tied in the minds of many that this graph “proved” that saturated fat was linked to heart disease—even though that is not what the graph shows at all. It isn’t even about saturated fat. Keys also neglected to mention Yerushalamy and Hilleboe’s data from 22 countries showed no relationship between total fat consumption and heart disease.
The Diet Heart Hypothesis
The diet-heart hypothesis originated with Ancel Keys and is the belief that eating foods high in saturated fat contributes to heart disease. Keys believed that replacing fat from meat, butter and eggs with newly-created polyunsaturated vegetable oils such as soybean oil would reduce heart disease and deaths by lowering blood cholesterol levels.
The Sugar Industry Funding of Research Vilifying Fat
In the mid-1960’s, the Sugar Research Foundation (predecessor of the Sugar Association) wanted to offset research that had been published and that suggested that sugar was a more important a cause of heart disease and stroke from atherosclerosis than dietary fat. The Sugar Research Foundation invited Dr. Fredrick Stare and the late Dr. D. Mark Hegsted of Harvard’s School of Public Health Nutrition Department to join its scientific advisory board and then approved $6,500 in funds ($50,000 in 2016 dollars) to support a review article that would respond to the research showing the danger of sucrose . Letters exchanged between the parties came to light a November 2016 article published by Kearns et al  which said that the Sugar Research Foundation had tasked the Harvard researchers with preparing “a review article of the several papers which find some special metabolic peril in sucrose and, in particular, fructose ”.
The Sugar Industry paying researchers to blame dietary fat and vindicate sugar for heart disease seems a little like the tobacco industry having secretly funded articles demonstrating that something other than smoking was responsible for lung cancer.
In August 1967 the New England Journal of Medicine published the first review article written by Drs. Stare, Hegsted and McGandy titled “Dietary fats, carbohydrates and atherosclerotic vascular disease” which stated;
“Since diets low in fat and high in sugar are rarely taken, we conclude that the practical significance of differences in dietary carbohydrate is minimal in comparison to those related to dietary fat and cholesterol”.
The report concluded;
“the major evidence today suggests only one avenue by which diet may affect the development and progression of atherosclerosis. This is by influencing the levels of serum lipids [fats], especially serum cholesterol.”
The Harvard researchers went on to say;
“there can be no doubt that levels of serum cholesterol can be substantially modified by manipulation of the fat and cholesterol of the diet” and that “on the basis of epidemiological, experimental and clinical evidence, that a lowering of the proportion of dietary saturated fatty acids, increasing the proportion of polyunsaturated acids and reducing the level of dietary cholesterol are the dietary changes most likely to be of benefit.”
At no point did Stare, Hegsted and McGandy disclose that they were paid by the Sugar Research Foundation for the two-part review.
A commentary in the Journal of Accountability in Research  summarized the significance of those articles as follows;
“Researchers were paid handsomely to critique studies that found sucrose [sugar] makes an inordinate contribution to fat metabolism and heart disease leaving only the theory that dietary fat and cholesterol was the primary contributor.”
The same Dr. Hegsted that was funded by the Sugar Industry to write the above articles vindicating sugar and vilifying dietary fat went on to work on editing the 1977 US Dietary Guidelines , which entrenched the vilification of fat into the US Food Pyramid for the next 40+ years. The rest, they say, is history.
The same year (1977), Canada’s Food Guide recommended that Canadians limit fat to <30% of daily calories with no more than 1/3 from saturated fat but did not specify an upper limit for dietary cholesterol. This was based on the belief that total dietary fat and saturated fat were responsible blood levels of LDL cholesterol levels and total serum cholesterol . Cholesterol in general (total cholesterol) and LDL cholesterol was assumed to be tied to heart disease, so the focus was on lowering the proxy measurements of LDL cholesterol and total cholesterol.
Recommendations for the continued restriction of dietary fat continued in both the US and Canada in the 2015 revision of the Dietary Guidelines based on the enduring belief that lowering saturated fat in the diet would lower blood cholesterol levels and reduce heart disease.
The question is does it?
A 2018 study published in the journal Nutrients looked at health and nutrition data from 158 countries from 1993-2011 and found that total fat and animal fat consumption were least associated with the risk of cardiovascular disease and that high carbohydrate consumption, particularly as cereals and wheat was most associated with the risk of cardiovascular disease . Significantly, both of these relationships held up regardless of a nation’s average national income.
These findings support those of the 2017 PURE (Prospective Urban and Rural Epidemiological) study, the largest-ever epidemiological study which recorded dietary intake of 135,000 people in 18 countries over an average of 7 1/2 years, including high-, medium- and low-income nations. The PURE study found an association between raised cholesterol and lower cardiovascular risk and that “higher carbohydrate intake was associated with higher risk of total mortality”. It also reported that “total fat and individual types of fat were related to lower total mortality (death)” .
A recent study published in the American Journal of Clinical Nutrition reports that long-term consumption of the saturated fat found in full-fat dairy products is not associated with an increased risk of cardiovascular disease (atherosclerosis, coronary artery disease, etc.) or other causes of death, and may actually be protective against heart attack and stroke .
This recent large-scale epidemiological data provides strong evidence that eating a diet containing saturated fat is not associated with heart disease. While eating saturated fat raises blood levels of LDL cholesterol, we now know that there is more than one type of LDL cholesterol and only the small, dense LDL cholesterol is linked to atherosclerosis. The large, fluffy LDL is protective .
We now know that fat was made out to be the villain in scientific reviews paid for by the sugar industry and this combined with Ancel Key’s Diet-Heart Hypothesis ended up being the impetus for the creation of an entire food industry designed to extract fat from industrial seed oils, such as soybean oil and rapeseed (Canola). These industrial seed oils are the so-called “healthy polyunsaturated fats” that we are encouraged to eat instead of so-called “dangerous” saturated fat, yet these industrial seed oils are only able to be produced using solvent-based chemical extraction under very high temperature. Should we be confident in industrial fats brought to us by the same industry that brought us “trans fats”? With a lack of evidence that natural fats such as butter or cream are dangerous, perhaps eating a bit of real animal fat and plenty of natural plant-based monounsaturated fats such as olive oil is the better way to go?
For more than forty years, generations of Americans and Canadians have avoided eggs, full fat cheese and creamery butter – and done so because they have believed that saturated fat raising LDL cholesterol predisposed them to heart disease. We know much more than we did in the 1970s when the first Dietary Guidelines were created in the US (under the watchful editorial oversight of one of the researchers that had been paid by the sugar industry to vilify fat). We now know that eating foods with saturated fat will raise LDL-cholesterol, but not all LDL-cholesterol is “bad”. Before we knew this high total LDL-cholesterol (LDL-C) was seen as a good proxy (indirect substitute) measurement for heart disease risk, but no longer.
It has been known since the early 1990s that a high TG:HDL ratio is very good estimator of coronary heart disease risk .
The measurement of the LDL-cholesterol particle number (LDL-P) which measures the actual number of LDL particles is a much stronger predictor of cardiovascular events than LDL-C  because the more particles there are, the more small, dense LDL there are.
The ratio of apolipoprotein B (apoB): apolipoprotein A (apoA) is another good estimator of cardiovascular risk. Lipoproteins are particles that transport cholesterol and triglycerides (TG) in the blood stream and are made up of apolipoproteins, phospholipids, triglycerides and cholesterol. Apolipoprotein B is an important component of many of the lipoprotein particles associated with atherosclerosis, such as chylomicrons, VLDL, IDL, LDL – with most found in LDL. Since each lipoprotein particle contains one apoB molecule, measuring apoB enables the determination of the number of lipoprotein particles that contribute to atherosclerosis and for this reason that ApoB is considered a much better predictor of cardiovascular disease risk than LDL-C .
In light of the recently published epidemiological evidence and much stronger proxy measurement of cardiovascular risk we must update our thinking that fat in general, or saturated fat in particular is the “villain”. It’s not.
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