Cholesterol Series Part 1: The Diet-Heart Hypothesis (is wrong)

We’ve been receiving quite a few questions about cholesterol recently. How to lower it, how much impact diet has on blood cholesterol levels, is it really that dangerous, etc. Perhaps these questions are coming up because February was National Heart Health Month? Probably not, but it seems as good a time as ever to share the facts about why you do not, and will not ever, need to limit your dietary cholesterol intake to protect your heart health. Even if you’ve been told your cholesterol levels are high, lowering it will not necessarily make you healthier.

Initially, I was going to write a blog explaining the history and the (comparatively) new-ish discovery of C-reactive protein as a better measure of heart health. It turned into more of a novella, so this will be a three part series. This week, we’ll cover the infamous Diet-Heart Hypothesis that should have died 40 years ago but still lives on in our collective psyche like the voice of our overbearing grandmother, convincing us that we’re bad little kids if we eat too much fat. If we want to find a better way, we’ve got to start by silencing this demon of bad science.

In the beginning…

Why are they always so concerned about our blood cholesterol level when we get a checkup? Well, it all started back in 1958 when a researcher named Ancel Keys came up with the Diet-Heart Hypothesis, in which he imagined that the fat we eat, especially the saturated fat, causes heart disease. And when I say “came up with” and “imagined”, I mean that literally. He really just made it up. He traveled the world gathering data from traditional cultures that supported the conclusion he had come to before he even started the study. His resulting personal crusade against fat resulted in the first US Government Dietary Recommendations in 1977, which suggested that everyone over the age of two should avoid dietary fat at all costs.

It wasn’t until 50 years later that Keys’ biases came to light and it was revealed that he cherry picked data in order to fit his hypothesis. He had data from 22 countries, but he only published the data from 7 countries. The other 15 didn’t fit with his theory. For those not mathematically inclined, that’s the majority, over two thirds of his own data that disproved his hypothesis. He was a very passionate guy, though. He wasn’t going to let a silly little thing like reality stand in the way of him making his mark on the world. So Keys lied and published a study including less than 1/3 of his actual findings. All of our generally accepted nutrition recommendations have stemmed from his lies. He (probably) had the best of intentions, but we continue to suffer.

Keys’ Influence

In my opinion, the worst part is that he was so influential, other researchers were afraid to contradict him. We may never know how many other studies from that time period were hushed up because they didn’t fit into his, by then, firmly accepted theory. Some of these hidden studies have come to light 50+ years later. The famous Framingham Heart Study has been ongoing for generations and turning out data right and left. It was accidentally discovered after decades, that a certain cholesterol finding during the height of Keys’ influence had been left in a box and unreleased. What were these findings? Oh, just that after age 55, the higher the cholesterol, the longer people lived. Far from killing people off with heart attacks, it seemed to be protecting them.

Here is an article from Scientific American about an eerily similar situation in which a well conducted study from around 1970 was boxed for not fitting the Diet-Heart Hypothesis narrative. A group of researchers in Minnesota spent 5 years feeding over 9,000 nursing home patients two different diets. One group ate a diet high in saturated animal fats, and the other group were fed unsaturated vegetable oils (mostly corn oil) as the majority of their fat. Keep in mind that these diets were literally fed to them, every single day. This wasn’t one of those, “tell people what they should do and hope they’re not lying about doing it” kind of studies. These were people in nursing homes, eating what was prepared and set before them.

And what did the study find after five years? “Vegetable oils lowered total blood cholesterol levels, by an average of 14 percent… But that lowered cholesterol did not help people live longer. Instead, the lower cholesterol fell, the higher the risk of dying: 22 percent higher for every 30-point fall. Nor did the corn-oil group have less atherosclerosis or fewer heart attacks.” That’s right, it found that the Diet-Heart Hypothesis is wrong. Not only does dietary saturated fat have less effect on serum cholesterol than Keys imagined, but far more importantly, lower cholesterol levels do not correlate with improved heart health outcomes. Eating less saturated fat does not improve heart health. This conclusion was considered so sacrilegious that it too was shoved in a box and not discovered for 40 years.

Science should not be treated like religion, but for some reason Ancel Keys’ Diet-Heart Hypothesis was, and even now that enough time has passed that it’s acceptable to release studies contradicting his dogma, the advice given to the masses remains basically the same. It should not be, and we’ll get into why in the next part of this series, What is Cholesterol and Why?. Then in the final part, we’ll discuss C-Reactive Protein, a simple measure that your doctor is probably already testing on every blood panel, and a much better predictor of heart health than cholesterol has ever been. Then at the end, we’ll show you what you can adjust about your lifestyle to actually improve your health outcomes.

For now, just know that dietary cholesterol is not your enemy. It is, in fact, much more likely to improve the health of every cell in your body.

And now…

Even now, it’s difficult to find research that isn’t tainted with the established “fact” that saturated fats are unhealthy. Even when a saturated fat link isn’t found in an individual study, you will almost always find that their conclusion remains “It is still advisable to limit saturated fat intake to prevent heart disease risk factors.” It’s as though their findings mean nothing unless they match the a prior beliefs about cholesterol that are already in the researcher’s soul. It’s not science, it’s faith.

I’ve also been frustrated by how often scientists will combine saturated fats with trans fats in their data as though they are the same thing. They are not the same, not even close. Trans fats are chemically manipulated, manmade, and damaging to our bodies. I’m unaware of any study involving these industrially produced trans fats that hasn’t found them detrimental to all aspects of human health. Combining these unnatural fats in studies with saturated fats which are natural and recognizable by our body as useful, makes no sense and leads to skewed conclusions.

Did you know that long before Ancel Keys came on the scene, one of the first cholesterol-heart disease studies was conducted in 1908, on rabbits? That’s right, rabbits. Vegetarian animals who don’t eat saturated fat or cholesterol at all, ever. They developed illness and heart disease from eating fats that were not normally in their diet. Of course they did. This has nothing to do with humans, but it seems to be where the idea for the Diet-Heart Hypothesis originated. Isn’t it time we progressed a little from this non-sensical conclusion?

But research is starting to come around.

With that background on how sketchy the research tends to be in this realm, here are a few of the better studies and reviews I was able to find that dare to refute the Diet-Heart Hypothesis:

Review of 110,704 diet-heart related studies: This is by far the most extensive review I have ever come across. Their conclusion was unqualified. According to the data from thousands of diet related studies, there is no evidence for any dietary fat intake leading to heart disease, except for the unnatural trans fats. “We found that higher dietary trans fatty acids (TFA) intake was associated with increased risk of cardiovascular diseases (CVDs)… However, no association was observed between total fat, monounsaturated fatty acids (MUFA), saturated fatty acids (SFA), and polyunsaturated fatty acids (PUFA), and risk of CVDs.”

Meta-Analysis of 21 studies on the association of saturated fat intake and heart disease: This review is more specifically targeted. They chose only studies that focused on dietary saturated fat and cardio vascular outcomes. They then compared the highest intake of saturated fat with the lowest intake, and found that intake of saturated fat was not associated with any increased risk of CHD, stroke, or CVD. It made no difference.

The Helsinki Businessman Study: In the 70s, this study was conducted on over 1000 men. Some were told to live normally, while others were screened quarterly for “heart disease risk factors” such as high cholesterol and high blood pressure, and given interventions, mostly medication, to improve these symptoms. Which they did. However, the study was terminated after 6 years because the men in the intervention group, despite doctors claiming they were now at a lower risk for heart disease, were dying (of everything) at a rate so much higher than the control group that it was no longer ethical to continue the experiment. Follow-up studies have found that this increased mortality continued for at least 25 years afterward. Yikes.


Despite what most researchers seem to think, the human body is smart. What if cholesterol is there for a good reason? Spoiler: It is. The amount that we eat has little to no impact on the amount we have in our body. So where is our high cholesterol coming from?
Next week, we’ll take a deep dive into what cholesterol really is and why the nature of what it does in our bodies has embroiled it in so much controversy.

Part 1: The Diet-Heart Hypothesis is wrong.

Part 2: What is cholesterol? And why?

Part 3: A better Measure of heart health. (CRP)

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