Why Saturated Fats Differ in Their Effects on LDL

Okay, so the next question I was really interested in myself, and it was submitted by David. David asks, is there a hierarchy of saturated fats in terms of causing harm by raising LDL? For instance, stearic acid from chocolate doesn't raise LDL much, and now I'm hearing more that the saturated fat in dairy doesn't raise LDL.

So, in a nutshell, let's just talk about mechanism here. Certain saturated fatty acids, so there's palmitic acid that's 16 carbons, there's myristic acid, which is 14 carbons, and then there's lauric acid, which is 12 carbons. Those have been repeatedly linked to downregulating LDL receptor activity in the liver. So, what does that mean? That means when you downregulate the LDL receptor, you make less of that receptor. And that LDL receptor is very, very important. You do not want to make less of it because that is what clears LDL out of your circulation, out of your bloodstream. And so when you have fewer LDL receptors on your liver, that leads to elevations in LDL particles in circulation, which then of course allows those LDL particles to lodge themselves in arterial walls, form plaques, form foam cells and all this. You get the beginnings of atherosclerosis.

Stearic acid is 18 carbons, and it is somewhat special. So, a decent fraction can convert to oleic acid, and this is a monounsaturated fat. So, it tends to not suppress the LDL receptor activity in the liver to the same extent as some of the other saturated fatty acids, like, for example, palmitic acid. And that is partly why chocolate, which is higher in stearic acid, is sometimes said to be "neutral" with respect to raising LDL.

So, what do the studies say? Well, let's talk about stearic acid. Some studies show that stearic acid tends to raise LDL less than other saturated fats. Again, because we're talking about less downregulation, less suppression of LDL receptors on the liver. However, if you replace stearic acid with an unsaturated fat, like a monounsaturated fat, you actually see even lower LDL. So, really, the best is to try to go for these monounsaturated, polyunsaturated fats before the saturated fat.

Palmitic acid, so a meta-analysis indicated that swapping out palmitic acid for unsaturated fat lowers LDL levels by a small but significant amount. Because palmitic acid is so common, so it's in palm oil, it's in butter, it's in fatty meat, it does make up a substantial chunk of many people's dietary saturated fat intake.

Now, let's talk about dairy fat, so butter versus cheese, for example. Butter consistently raises LDL in studies, very consistent. Interestingly, cheese, so dairy that is cheese, seems to have a weaker impact on LDL than you'd predict from its saturated fat content alone. And I think that's because of the so-called matrix effect. And we've talked a little bit about this in previous Q&A. So, calcium and protein, plus the unique structure of cheese, can bind some of these fatty acids, some of these saturated fatty acids. So, less of those saturated fatty acids are actually absorbed into circulation. And the net effect then is that cheese can raise LDL less than butter or palm oil, even though it still has a similar amount of the saturated fatty acids.

Now, coconut oil, the composition of coconut oil is lauric acid. I mentioned that was 12 carbons. It's also got myristic acid and palmitic acid. Now, while there is between virgin coconut oil and refined coconut oil, most meta-analyses still suggest coconut oil raises LDL more than many unsaturated fatty acids, so monounsaturated or polyunsaturated fatty acids. It doesn't seem as potent at raising LDL as butter in all studies, but the overall takeaway is if you are trying to lower your apoB and LDL, coconut oil is not neutral.

And I've personally experimented with this and found that I was able to drop my LDL particle number significantly. Many, many years ago, I used to cook with coconut oil, over 10 years ago. I used to cook with coconut oil, and once I cut that out, my particle number dropped. I mean, it was a significant amount. I don't remember because it was so long ago, but it was quite significant.

Okay, so I would say in general, stearic acid, which is something that's higher in chocolate, for example, or cocoa butter, it is the less concerning end of the saturated fat spectrum from a purely LDL-raising standpoint. Lauric, myristic, and palmitic acids, which really dominate in coconut oil, palm oil, butter, many processed foods, like peanut butters, you'll find palm oil in a lot of processed foods, popcorn, for example, they tend to have more consistent LDL-raising effects.

However, food does matter. So, palmitic acid in the context of a diet that's high in fiber or cheese has that "matrix effect." And I think that has been shown to yield a different net effect on lipids than if you're just consuming the palmitic acid from processed foods, fried foods, for example. So, really what I'm talking about here is cheese dairy versus the palm oil and the stuff that you're finding in the processed foods.

I do want to also stress that focusing on a single fatty acid in isolation sort of misses the broader point. It really is more about overall diet composition and the net effect on apoB-containing lipoproteins. There's a lot of really solid data showing that replacing saturated fats with monounsaturated fats or polyunsaturated fats typically lowers LDL and total apoB. So, you'll see a lot of improvements there with a lot of different prospective studies looking at cardiovascular outcomes.

You also want to make sure you're not replacing these fats with added sugar, with ultra-processed foods, things that are found in refined carbohydrates. That is also damaging to cardiovascular health. And so, if you swap out saturated fat with the ultra-processed foods and refined carbohydrates, you are not doing yourself any benefit. So, you're better off, honestly, replacing saturated fatty acids with things like avocado, avocado oil, olive, olive oil, salmon, right? These are the good sources of monounsaturated, polyunsaturated fat. Nuts. These are fatty acids that are not going to raise apoB.

And cooking, I think cooking with avocado oil and olive oil is ideal and better than cooking with butter. Also, what's the big one? I think people are really interested in cooking with beef tallow. I don't know that that's a great idea for someone interested in lowering their apoB number because it's so high in—I think it's really high in the palmitic acid. So, you're really getting a really high, high, high dose of that while you're just using it to cook. And honestly, you can just be using avocado oil to cook.

Josh Mitteldorf is asking how strong the evidence linking LDL to cardiovascular disease. I would say it's pretty darn strong. I would say it's pretty strong. I know there's been a big sort of push that, "Oh, saturated fat's not as bad as we thought," and I think that the bigger take-home message there is that replacing saturated fat with refined carbohydrates is not the way to go. And that's what a lot of people did. Replacing it with trans fats, like margarine, is actually worse. And that has a lot to do with the properties of these hydrogenated oils, which essentially, the carbons strung together are not flexible. And so, you have a really stiff fatty acid.

And those fatty acids get incorporated into your cells. You need fatty acids. They get incorporated into your cells, and they're a part of the cell membrane. And what happens is when all those cells lining your blood vessels, your arteries, when they incorporate the trans fats, they can't bend and move. And so, they get real stiff. And stiffness of blood vessels and arteries is a major contributor to cardiovascular disease.

So, I think that there was a big sort of correlation doesn't equal causation with respect to, "Oh, with saturated fat, look what happens when you lower your saturated fat, your cardiovascular disease risk doesn't go down." Well, turns out lots of studies that swapped out saturated fat with polyunsaturated fat, cardiovascular disease risk did go down. When they swapped it out with a lot of refined carbohydrates, cardiovascular disease risk did not go down. So, it's really, again, a food-first approach. You have to look at what you're eating. It's not just about these fatty acids in isolation. It's the whole foods.

So, I do think we pretty much know for a fact that high LDL particle number, high apoB is detrimental for cardiovascular health. And there are people, for example, that have single nucleotide polymorphisms in their PCSK9 gene, which lowers it. And these people have the lowest cardiovascular rate of mortality. They're living a long time, and they're not getting cardiovascular disease. Now, keep in mind, PCSK9 is a target now for drugs. There's a lot of people actually take these PCSK9 inhibitors. They get injections every few weeks, and that also sort of is mimicking what these people that naturally have a low amount, a low version of this gene, what they're doing. And so, sometimes you can look at genetics and go, "Wow, people that have a low amount of this LDL are living longer, and it's sort of more of a causal effect that you won't find from a lot of dietary studies."