Is saturated fat unhealthy?

Saturated fat deadly unhealthy

In a sense, I can’t believe I’m writing this article. From a scientific perspective, this issue has been firmly settled. The answer is very clearly “NO!”. And yet, if I google “is saturated fat unhealthy?”, then seven of the top nine results proclaim with great certainty that “yes, it is”.

Here’s what the NHS says to people living in the UK: “Too much saturated fat can increase the amount of cholesterol in the blood, which increases your risk of developing heart disease.”

And here’s what the US government tells its citizens: “Eating too many foods high in saturated fats can be bad for your health. By replacing saturated fats with unsaturated fats, you may lower your risk of getting heart disease.”

To be fair, the US government doesn’t sound quite as confident as the UK health authorities. There’s a lot of “can” and “may” in that sentence. Which is actually a bit funny, when you consider that it was the US government that got the whole world to cut down on saturated fats in the first place.

Interestingly, none of the self-appointed fact checking organizations that have sprung up in recent years has yet tried to pull the NHS or the US government off the internet for spreading misinformation.

The claim that saturated fat is unhealthy originated with physiologist Ancel Keys in the mid-part of the twentieth century. He initially believed that cholesterol in the diet was what caused heart disease. Unfortunately, he soon noticed that feeding people cholesterol had no effect whatsoever on the cholesterol levels in their blood streams. So he was forced to abandon that line of thinking. On doing some further research, he noticed that increasing the proportion of saturated fat in the diet did however appear to increase cholesterol somewhat.

This led him to develop the diet-heart hypothesis, which basically says the following: Saturated fat in the diet leads to increased cholesterol levels in the blood stream, which causes heart disease. So it’s a two part hypothesis. As I’ve already discussed before on this blog, the second part of the hypothesis has been disproven – cholesterol in the blood stream does not cause heart disease.

But what about the first part? Even if not through the intermediate action on cholesterol, saturated fat might still somehow be unhealthy. Ancel Keys claimed to have evidence that high levels of saturated fat in the diet correlates with heart disease. This evidence came from a very shaky observational data set called the “Seven Countries Study”, in which Keys presented results from relatively small, hand-picked cohorts in seven countries, which appeared to show a correlation between saturated fat intake and heart disease (and ignored data from a bunch of other countries where no such correlation could be seen).

But it’s now more than forty years after the Seven Countries Study was published, and there is thus no reason to rely any longer on what Ancel Keys claimed to have found. We can instead look at the wealth of data that’s been produced since then.

Let’s start with what the observational data show. A meta-analysis was published in the American Journal of Clinical Nutrition in 2010 that sought to find if the prospective cohort studies that had been carried out up to that point supported the notion that saturated fat causes heart disease.

A meta-analysis is a pooled analysis, where you take a bunch of studies and add their results together, to get a higher degree of statistical accuracy. A prospective cohort study is a study where you find two groups of people that vary in some significant respect, for example in terms of how much saturated fat they eat, and then follow them over time to see what happens – it’s generally considered to be the highest quality type of observational study, although it doesn’t reach the level of quality of a randomized controlled trial, because it isn’t able to get rid of confounding effects to the level that a randomized trial can (if you need to brush up on scientific method in the health sciences, read this).

Why are we even bothering to look at observational studies at all then, instead of just jumping straight to randomized trials? Because observational studies are easier to do, so there are more of them, and they can gather a lot more data. While a randomized trial with a few thousand people is huge, an observational study with a few thousand people is tiny. Additionally, as mentioned, the initial recommendation to eat less saturated fat was based on a single observational study, and quite a small one at that (the Seven Countries Study included less than 13,000 people – “Seven Countries” makes it sound much bigger than it was). So it’s interesting to see if the vast mass of observational data that we have today bears out the initial findings of the Seven Countries Study.

The authors of the meta-analysis identified 21 prospective cohort studies, with a total of almost 400,000 participants. That’s a big data set. The studies followed participants for between five and 23 years.

So, what did they find?

The difference in risk of cardiovascular disease between the groups with a high intake of saturated fat and those with a low intake of saturated fat was exactly zero. There was no difference at all. If you look more closely at the different kinds of cardiovascular disease, then you see a slightly increased risk of coronary heart disease in the saturated fat group (7% increased relative risk), but a slightly decreased risk of stroke (21% decreased relative risk). Neither of those differences were statistically significant, however. And in observational data sets, with all the risks of confounding they face, anything less than a halving or doubling of risk should be ignored, since small differences between groups are almost certainly caused by confounding factors.

Let’s move on and look at what the randomized controlled trials show. A Cochrane review was published in 2020 that looked at the ability of a diet low in saturated fat to prevent heart disease and death. 15 trials were identified, with a total of roughly 55,000 participants, and included in Cochrane’s meta-analysis. In most of the trials, the intervention consisted of dietary advice, although a few also provided polyunsaturated fats (so-called “healthy oils”), and told people to replace their lard and butter with them, and one provided participants with complete meal replacements. The trials lasted from two to eight years, with an average duration of five years.

Eleven of the 15 trials measured intake of saturated fats at multiple time points, and could thus confirm that intake of saturated fats decreased in the intervention group as compared with the control group. This is good to know, since if that wasn’t the case then a lack of benefit in terms of heart disease risk could simply be due to not managing to get people to change their diets sufficiently. So we know for certain that saturated fat intake decreased in at least eleven of the fifteen trials. Did this have any meaningful impact on people’s risk of having a heart attack or dying?

No, is the short answer. In the low saturated fat group, 6.4% of participants died, while in the high saturated fat group, 6.2% of participants died. So 0.2% more people died in the low saturated fat group than in the high saturated fat group. As you would expect for such a small difference, it isn’t statistically significant.

After the dark magic known as Mantel-Haenszel weighting (a statistical technique used in meta-analysis in which studies with more precise results are given greater weight), the authors reach the conclusion that it’s actually the other way around, that marginally less people should have died in the low saturated fat group, but the difference still isn’t statistically significant.

So it’s not possible to conclude that a diet high in saturated fat increases overall mortality. What about if we look specifically at heart attacks?

Most heart attacks are not fatal, so it’s possible that an intervention could lower heart attacks without meaningfully impacting overall risk of death. In the low saturated fat group, 3.3% of participants had a heart attack. In the high saturated fat group, 3.1% of participants had a heart attack. So the people in the high saturated fat group actually experienced fewer heart attacks than the people in the low saturated fat group.

Again, after statistical weighting, it appears that there should have been slightly fewer heart attacks in the group with the low saturated fat diet (rougly 0.3% less). Just as before, however, the difference isn’t statistically significant. What that means is that the small difference that was found is within the margin of error.

To conclude, the sum of all the observational and randomized trial evidence now available to us does not allow us to conclude that there is any increased risk of cardiovascular disease or death with increased intake of saturated fat. Considering that the data sets that these conclusions are based on are massive, we can be certain that even if there were a benefit, it would be so tiny as to not be worth bothering with. It is therefore shocking that public health agencies still tell their populations to cut down on saturated fats, instead of focusing on the things that have actually been shown to make a difference.

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39 thoughts on “Is saturated fat unhealthy?”

  1. Big Pharma is missing out big time here. They should be making saturated fat pills. Dose would be the approximate amount of fat in a rasher of bacon. They can get the raw material almost for free from any industrial farm. 🤔 maybe I should shut up and do this myself.

      1. I first began to consider all those lies when I came across Dr. Chris Masterjohn (https://daveasprey.com/podcast-16-everything-you-need-to-know-about-saturated-fat-cholesterol-with-chris-masterjohn/) That was a before/after for me.
        Next I learnt about the oxidative theory and some others. Result: today I am rather confused 🙁
        When studying Diethetics (2004) we were told that saturated fats, because of all their atoms being “occupied”, made them almost impossible to combine with other molecules -that being supposedly “bad”. Palm oil, for exemple, was kind of a devil. However, precisely due to this (according to the Keto diet, this is “good” and make them “stable” -ie. high or none oxidation point) some consider them “good”. Who can please make this clear once and for all?…

    1. before vaccines, there were statins – the most lucrative of drugs, with annual revenue of $1tri.

      but saturated fat in the body negatively correlates to covid severity.

      so the saturation of industrially-extracted seed oils throughout our food system was the perfect set-up for vaccine desperation.

      and the vaccines seem now in some way to further compromise our health.

      its all going swimmingly top class and stylishly sweet.

      oh to be a learned one. I would be so wise.

  2. Hi Dr. Rushworth
    7 countries included Finland. It means 200 forestry workers in Eastern Finland, who “spread butter on hard cheese”. And they did smoke.

    Interestingly, Dr. Kendrick combines them with former sovjet states liberation and consequent stress or strain in his words. Which causes CVD…

    The Finns made a massive relocation of 400k people from russian conquered territory. It is stressful. Where did they get land: existing farmers. Which is stressful. I must guess now that the most burden was in the east.

    Western Finns have a different gene pool than Eastern Finns. They would not have fitted into Key’s study, by health and by habits.

    But the sat fat got the blame. Subsequent margarine project coincided with smoking diminishing, read, proving that sat fat was to blame and margarine was the hero.

    The guy advanced to Finnish Fauci and he is still circulating those “Karelia project” advances…

    I do shame these “advances”…
    JR

    1. 7 countries included Finland. It means 200 forestry workers in Eastern Finland, who “spread butter on hard cheese”. And they did smoke.

      Interestingly, Dr. Kendrick combines them with former sovjet states liberation and consequent stress or strain in his words. Which causes CVD…

      That’s not what Kendrick said; he proposed that it was the breakup of the Soviet Union and the subsequent destruction of the Soviet social system that created the stress, NOT ‘liberation’. He compared it to countries with massive dislocation of populations due to war, refugees, exile and so forth.

  3. You say:
    “It is therefore shocking that public health agencies still tell their populations to cut down on saturated fats, instead of focusing on the things that have actually been shown to make a difference.”

    Care to tell us what definitively does make a difference?

      1. I believe Sugar is the correct answer. Seems that sugar glycation is the missing variable in those cholesterol heart studies. Saturated fat is generally paired with protein and the amino acid lysine. Sugar glycates the lysine in LDL turning it bad.

        By the way, Lysine has been found to strongly inhibit viral replication including that of covid by decreasing Arginine uptake which viruses love. You’d also want to decrease Arginine by cutting out nuts and seeds. Getting your lysine from food is not enough, you need to supplement with at least an additional gram for the antiviral benefit.

        I wonder if a carnivore diet would give you enough lysine to be covid protective. We normally get about a gram of Lysine per day but that’s not enough. A pound of beef has 10 G of Lysine. Pushing people away from meat eating would be a great way to make them susceptible to viruses, but the powers-that-be certainly would never do that, would they?

    1. What does make a difference is restriction of the bioactive lipids linoleic acid and arachidonic acid. Saturated fatty acids are not bioactive lipids. They cannot do what this narrative asserts. “High intake of dietary saturated fatty acids has been associated with obesity, cardiovascular disease and diabetes in humans. Some of the basis for this association has been attributed to the ability of saturated fatty acids to promote inflammation and insulin resistance, as well as to increase adipose accumulation and risk of obesity.” (excerpt from pages 5-6 of a 2019 Master’s Thesis entitled “Broiler chicken development: from genetic regulation to rural Rwandan production.”) Look that up and read pages 6-9. The author explains how and why excessive linoleic acid intake causes both chickens and humans to accumulate belly fat.

      That narrative is what is currently being taught in almost every university in the World that graduates students with degrees in the health sciences. It’s what all the bureaucrats in government agencies who formulate dietary advice believe. It’s what all policy advisors to political leaders believe. It has been so firmly entrenched in academia and government for so long that it will likely require political action to expose the fallacy. That’s not going to happen until politicians take an interest in the matter. No sign of that happening as yet.

  4. Makes me feel better about cooking in ghee — far better than overheating olive oil or other nastier oils. And I must have a little bit of butter for my bread (as the King told the Queen and the Queen told the parlour maid).

    What about people with congenitally high cholesterol levels? I heard that high levels in India caused increased rates of heart disease and resulted in them understandably using less ghee for cooking. Should other means of reducing cholesterol be used?

    1. High cholesterol is not that much of a problem. Certainly after 60 it is all cause mortality protective; especially for women. People with low cholesterol (male and female) die younger. Read Malcolm Kendrick’s (cardiologist) books.

  5. Another excellent article, thx.

    So, would it follow that you can’t reverse heart disease through diet?

    Was the Dean Ornish study which was more than just changes in diet a good analysis?

    1. No.
      Oxidative stress causes arteriosclerosis.
      Cholesterol is required for arterial repair. Too many repairs in rapid succession lead to constriction.
      At the end of this link is a better explanation of how it works. Personally I wouldn’t follow any of the diet advice in the link but the science looks the goods.
      https://therootcauseprotocol.com/

    2. Ah, but one can reduce risk for heart disease by altering arachidonic acid and linoleic acid intake to levels that meet physiological requirements. Swapping animal protein for plant protein will result in lower concentrations of arachidonic acid in cell membranes. This, in turn, reduces inflammatory cell signaling. For the scientifically curious, I suggest Googling Anna Haug arachidonic acid and Olaf Adam arachidonic acid. Excerpt from a 1992 Review by Olaf Adam entitled Immediate and long range effects of the uptake of increased amounts of arachidonic acid. “Within the last 50 years, changing nutritional habits in Western communities led to a fourfold increase in the supply of dietary arachidonic acid (AA), provoked by the same increase in the consumption of meat and meat products.”

  6. What does make a difference? My guess is smoking and genetics.
    I’ve always had cholesterol in the 230 range. At 63 years old I had a heart cath/ultrasounds/scans done and the doctor told me “You have no plaque anywhere in your body…clean living!” Ha, if he only knew!

    The doctors STILL tried to put me on statin drugs to reduce my cholesterol and I asked “Did you even read my charts?”. My suspicion is that with the current “zeitgeist” in the medical community such that cholesterol is still a boogie man, they must prescribe statins at a certain age or they will be sued if the patient has a heart attack…because cholesterol! AKA CYA (Cover Your Ass)

    1. I liked the description of an NHS cardiologist of the state of my arteries: “clean as a whistle.”

      In spite of which my GP wanted me to take statins. He did me a favour; ever since I have been sceptical of the advice of doctors. Not uniformly disbelieving, just sceptical.

      One of the great advantages of your blog, doc, is that you send us to look at evidence. Keep up the good work!

    2. Genetics: I can just look at sugar – or a piece of bread – or a cigar – and my arteries will plaque! Let alone eat them… My cholesterol is very high too (300+ these days) – and I’ve gone back on statins based on my doctor’s advice… Though I doubt they do me much good: I was on statins for years – and plaque developed year after year… I cut out a lot of carbs the last couple years. not obese, etc.. Genetics.. or What?
      My dad died of a heart attack at 50. I’ve made it to 67 – and feel fine despite it all – No heart attacks, stents or bypasses or anything like that yet (besides ear operation and cataracts).
      My maternal granddad made it to 91 – with bad angina – popping nitro tablets as he walked along near the end.

      1. Sorry to bother you – but have you had your thyroid checked? Thyroid hormones are built from cholesterol. If you‘re hypothyroid the cholesterol might simply not be used. Hypothyroidism increases the risk of heart problems. You can check yourself. Is your pulse low? How is your body temperature in the morning? Have a doctor check your TSH. And don‘t get L-thyroxin, it makes things worse. Get a combination of T4 and T3.

  7. Translation of the Dutch government advice:

    “Saturated fat increases the risk of cardiovascular disease. This is because saturated fat can cause the ‘bad’ LDL cholesterol in your blood to rise and as a result your blood vessels can slowly clog up. Choose products with little saturated fat and replace them with products with unsaturated fat.” (https://www.voedingscentrum.nl/nl/service/vraag-en-antwoord/gezonde-voeding-en-voedingsstoffen/welke-vetten-zijn-ongezond-.aspx)

    This is kind of scary to read. Why does their advice not reflect scientific consensus?

  8. Yes also see the ethnographic study the ‘Roseto Effect’ here rates of heart disease in a community of ‘lard’ eating Italians was very low. The author concluded that social cohesion was the key protective variable/subsequently lost in subsequent generations who became more individualistic.

  9. See also video The Great Leveller its available on YouTube has Whitehall Study as well as Roseto and all sorts of other stress related stuff.

  10. According to Dr Malcolm Kendrick, there is no one, cause of heart disease but just look at the most prevelent symptom, and also the one hardest to quantify; stress.

  11. “Children being treated for transgender issues at Sweden’s Karolinska University Hospital have allegedly suffered severe injuries as a result of hormone puberty blockers.”

    This is what happens when people go to war against biology.

  12. “Cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid and vitamin D”

    vitamin d… hmm… where have I ben hearing about that lately…

  13. Look at nature. Fish in cold waters are rich in unsaturated and poor in saturated fatty acids. Fish in warm waters are rich in saturated and poor in unsaturated fatty acids. If you live in cold areas, unsaturated fatty acids are fine. In the tropics, it should be saturated fatty acids. Cholesterol is needed for the formation of vitamin D via sunlight. Nature has already ”thought this through” well. I have not yet found a book on nutrition where it is taken into account where on earth the reader lives. In addition, the type of fatty acids should be adapted to the season.

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