TL;DR – an exhaustive look at past research finds a lack of evidence for many decades of telling us to avoid saturated fats. A review indicates early research, much of it promoted by Ancel Keys, Ph.D., Ph.D., did not differentiate between trans fats and saturated fats in the study participants. Artificial trans fats are now known to be bad and have been banned as food additives in the U.S. (since 2018). The effect, though, was to recommend avoiding all saturated fats when trans fats were the likely culprit, not natural saturated fats. 50 years of dietary advice to avoid saturated fats may have been wrong.
Trans fats, such as hydrogenated cottonseed oil (Crisco) are semi solid and shelf stable at room temperature, and thus, were commonly used in both commercial and home baked goods (such as cookies, pie crusts, etc). Mary Enig, Ph.D., first alerted the problems of trans fats in 1984 and suggested that earlier research had co-mingled both trans fats and saturated fats. Not until early in the 21st century did concerns over trans fats rise to a high level; in 2007, Crisco introduced a new formulation to reduce trans fats. In 2006, the government required trans fats be shown on food labels and by 2018, trans fats were largely banned in the United States (with effective date in 2021).
Decades were spent telling the public to avoid most fats, and saturated fats specifically. This had consequences including increased consumption of sugars, high GI carbohydrates and polyunsaturated fats and high Omega-6 seed oils.
As a result, since the mid-twentieth century, the diets in the US have gradually shifted away from traditional whole foods toward imitation and ultra-processed foods which often contain high-fructose corn syrup, refined grains, synthetic vitamins, preservatives, and other additives, which are not nutritionally equivalent to whole foods. As a result, the US has experienced increasing rates of metabolic disorders in people of all ages, and it is reasonable to believe that this new epidemic is related to this major shift in dietary patterns. This will be discussed in greater detail below.
Despite its numerous flaws, the lipid–heart hypothesis continues to permeate dietary guidelines. Although the presence of trans-fat in the food supply will now diminish, the errors that trans-fat caused as ΔS have not been corrected, and the warnings against natural saturated fat continue. High linoleic acid consumption, ΔP, continues to be promoted, and the warnings regarding total cholesterol, LDL-C, and dietary cholesterol are constantly repeated. These remain ingrained in the popular media and in the public mind. The lipid–heart hypothesis continues to be a central paradigm in dietary guidelines although there is abundant evidence that it is erroneous.
No aspect of diet correlated with the development of CHD, including daily intake of cholesterol, total fat, animal fat, PUFA/SFA ratio, or calories [86]. William Castelli, who was director of the Framingham Study from 1979 to 1995, lamented in a 1992 paper, more than 40 years after the study began, that “Most of what we know about the effects of diet factors, particularly the saturation of fat and cholesterol, on serum lipid parameters derives from metabolic ward-type studies. Alas, such findings within a cohort studied over time have been disappointing, indeed the findings have been contradictory. For example, in Framingham, Massachusetts, the more saturated fat one ate, the more cholesterol one ate, the more calories one ate, the lower the person’s serum cholesterol”
As many other causes of death (water borne illnesses, childhood diseases) became controlled, death due to heart disease went from 4th most common cause of death one hundred years ago, to #1. People no longer died in childhood and eventually became elder adults – who died of heart problems – with heart disease now the #1 cause of death (but again, in part, because we eliminated many other causes).
The reduction in smoking is the largest factor in the reduction of heart disease. Other factors include improved management of blood pressure, elimination of trans fats and the widespread use of statins (for those who can tolerate them – I cannot, unfortunately). Update: I am reading a book by a French medical researcher who goes through many studies that did not show improvements or only minor improvements from statin usage in reducing heart disease. It has been noted that 50-75% of patients with stroke or heart attack have normal levels of cholesterol. Statins also have bad side effects for many.
There was a particularly striking increase in adult obesity between 1980 and 2000 during the time that the first four editions of the DGA were published along with the first Food Pyramid in 1992 which encouraged six to eleven servings of grains daily and minimal fat intake. [134]. In 1971–1974, 16.4% of US children and adolescents aged 2 to 19 were overweight (10.2%), obese (5.2%), or severely obese (1%), but by 2017–2018, this figure had more than doubled to 41.5% who were overweight (16.1%), obese (19.3%), or severely obese (6.1%) (see Figure 5) [135].
A 1987 New York Times article on the cholesterol controversy suggests that Keys had softened his position on cholesterol: “I’ve come to think that cholesterol is not as important as we used to think it was… Let’s reduce cholesterol by reasonable means but let’s not get too excited about it” [158]. Keys made this statement three years after he abandoned his efforts to prove his equation and around the time that the first paper with the partial results of the unsuccessful Minnesota Coronary Experiment was being prepared for the publication in which he was not included as an author. The lipid–heart hypothesis should be abandoned, as Keys himself appeared to be saying in 1987. However, as this historical review has noted, the lipid–heart hypothesis has not only failed to prevent heart disease, but it has also harmed the overall health of people, from children to adults, in so many ways. Using the lipid–heart hypothesis as support, natural diets are being replaced by synthetic diets with dire consequences for global health.
Research identified numerous errors in nutrition recommendations that caused actual population wide harm – yet up to today, we are still advised to avoid natural saturated fat:
Yet, decades later, the public is still advised by the DGA 2020–2025 to consume a low-fat diet of 20 to 35% of total calories, to limit intake of foods containing natural saturated fat, to limit saturated fat intake to less than 10%, and to consume as little dietary cholesterol as possible. In addition, the DGA 2020–2025 continues to promote the consumption of unsaturated high-linoleic oils, presumably to lower serum cholesterol levels, but at the expense of natural nutrient-dense sources of fat, like whole-fat dairy, eggs, and meat, for which the actual saturated fat content has been exaggerated, as discussed in Section 6.1.
Instead, the Committee should formulate dietary patterns comprising whole foods that address the diversity of cultures in the US and beyond and should discontinue the recommendations to consume only fat-free or low-fat dairy and to limit the consumption of cholesterol-rich but nutrient-dense foods like eggs and meat which contain not only SFA but also MUFA and PUFA and are rich in choline, vitamins, and minerals. The DGA 2020–2025 recommends consuming a variety of proteins, vegetables, and fruits and could certainly recommend consuming fats and oils from a variety of sources to achieve a balance of SFA, MUFA, and PUFA. The Committee should discourage the consumption of imitation and ultra-processed foods, heavily hydrogenated fats, which are still allowed by the FDA, excessive amounts of high-linoleic oils, and reheated fats and oils, which accumulate oxidized byproducts. The Committee should also consider including starches used for bulk and texture as “added sugar”, particularly in foods for infants and very young children, and encourage the consumption of whole grains, rather than setting a limit that allows 50% of grains to be refined, which are depleted of fiber and other important nutrients. Finally, the DGA 2025–2030 Advisory Committee should review the body of evidence on the benefits of low-carbohydrate and very-low-carbohydrate diets for people with insulin resistance disorders and reassess the AMDR for carbohydrate. In summary, the DGA 2025–2030 should reconsider its support for the lipid–heart hypothesis and promote the shift of the American diet back to traditional whole foods and away from fabricated fat-modified foods to overcome the current epidemic of metabolic disorders, which would in turn reduce the prevalence of cardiovascular disease.
The lipid–heart hypothesis should not be used in the formulation of dietary guidelines.
Many of us grew up on skim milk – because the “no fat” eating style was massively promoted. We used polyunsaturated, highly processed seed oils (which are now questioned too). If we had baked goods, like home baked cookies, they were made with Crisco hydrogenated cottonseed trans fats. (As an adult I developed an allergy to cottonseed.)
At one point, we were taught to avoid as much fat as possible – but that sugar was not a problem if we were not diabetic.
We were taught to consume large quantities of grains – anything to avoid fat. In the early 1990s, the USDA issued Food Pyramid drawings that implied about 60% of calories should come from grains, which for most meant refined white flour. Many nutritionists extrapolated the drawing and recommended that 50-60% of calories come from grains (which for most people meant white flour, not whole grains).
Remember “fat free yogurt” that contained lots of sugar? Remember “fat free” cookies sold in the grocery stores? Remember potato chips made with “Olestra“?
For many decades it appears our government and media obsession with “eating healthy” had little to no evidence to support it, and in many instances, may have caused actual health harms.
Current Thinking on Cholesterol
Regarding cholesterol, as best I can tell, the original cholesterol hypothesis had little good evidence – just poor-quality science to back it up. In the 1980s, the focus was on “total cholesterol”. Eventually that evolved to the distinct types of HDL and LDL. And today, a more nuanced focus on LDL together with other inflammatory components.
Up to today, there are news articles telling us to avoid cholesterol in food (which is now known as a minor component of cholesterol in our blood), and to avoid saturated fats. This convinced some that their personal dietary style (low fat, Mediterranean, vegetarian, vegan, etc) is the one true diet. How to eat became a religious, faith-based activity – complete with participants evangelizing others into their one true way of eating.
Today, the view on cholesterol has evolved – its no longer about total cholesterol but the constituents of cholesterol – HDL, LDL and the components carried by LDL and the blood.
Current thinking seems to be that cholesterol, per se, may not be the culprit in heart disease. Instead, inflammation of the arteries is the problem – and that inflammation may be caused by apo-B, Lp(a) and homocysteine, which are known to cause inflammation in the arteries. Inflammation is said to be the culprit – and there could be many causes of inflammation including components of LDL, and oxidized LDL.
Homocysteine levels rise in the midst of vitamin B deficiencies – notably B6, B9 and B12 – the latter may occur among those who pursue a long-term plant-based eating style, are older, have certain health conditions or take some medications (many diabetic medications interfere with B-12 absorption). It is correctable by taking B-12 supplements – or eating meat – and for some, by having periodic B-12 injections.
Paradoxically, vegans and vegetarians who pursue that eating style for a longer period tend to become B-12 deficient, raising their homocysteine levels and increasing their heart disease risk. (While high homocysteine is correlated with clogged arteries, unfortunately, lowering it by taking B-12 has not correlated with a reduction in heart disease in the studies done so far.) High homocysteine may negate the perceived benefits of vegan/vegetarian eating.
Many vegetarians/vegans like to say they are “healthier” than 95% of the population, even 99%, because their lipid panels are normal or low (so were mine for ten years). But it appears these claims may be erroneous as these biomarkers might not be as important as once thought.
Note – I have no expertise in any of this. My background is computer engineering. However, as I learned, following and “trusting the experts” led to serious health problems vis a vis my B-12 deficiency. I’ve done my best to read 4 books on the topic, plus published papers in the field to try and understand what is going on. The above two paragraph summarize what I think is the contemporary thinking about this. But as a brain injured idiot, I am probably wrong – which seems to put me in good company with nutrition scientists who have been mostly wrong for 50 years 🙂
And finally, we have the problem of dueling experts. The mainstream view is that LDL is a problem and should be lowered by most people taking statin drugs. Then there are other experts who say that statin drugs cause harm – and that lowering cholesterol is not delivering the perceived benefits. What are us ordinary people supposed to do? This is the problem of dueling experts which are common in subjects and fields where the uncertainty is probably large – enabling there to be valid yet opposing viewpoints.
