Article at a Glance
- New science demonstrates that, for most people, dietary cholesterol, in foods like eggs and salmon, is not absorbed and has very little do with levels of cholesterol circulating in the blood.
- The body makes most of its own cholesterol.
- However, about 20-30% of the population are “hyper absorbers” and need to watch cholesterol intake because it can affect LDL levels.
- Certain strains of bacteria living in the gut can transform cholesterol into a substance known as TMAO, which the New England Journal of Medicine has linked to heart disease.
For a different take on eggs, and when to exclude them from the diet, check out my recent interview with Chris Masterjohn, PhD.
I just finished a delicious breakfast of three scrambled pastured eggs cooked in ghee, half an avocado, and some roasted brussel sprouts.
Prior to breakfast, I went for a run and listened to Joe Rogan interview Chris Kresser on his podcast. I am fans of both of these guys, but in my view, a snippet of their conversation about the health implications of eating eggs and cholesterol lacked nuance, so I decided to write this blog to get a few things off my chest.
Do eggs have too much cholesterol?
Not for most of us.
We’ve touched on it here before, but it bears repeating: in many people, consumption of dietary cholesterol does not equal elevated levels of blood cholesterol.
No arguments there.
However, not everyone absorbs cholesterol at the same rate. Some, known as hyper absorbers, take in considerably more cholesterol than do others, and for them the increased absorption causes the liver to make VLDL, which once it sheds its triglyceride rich load, becomes LDL-C. (R)
Elevated LDL-C and LDL-P means increased risk for heart disease and depending on how high levels get, all cause mortality as well. One of the drivers of increased absorption of both cholesterol and plant sterol are the ABCG8 and ABCG5 genes, markers I have talked about in my posts on sterol sensitivity and absorption.
For more on how high fat diets affect heart disease risk, check out our first podcast episode: Ketogenic Diets: the Good, the Bad and the Genetic.
In the Joe Rogan episode, Joe and Chris refer to the emerging consensus about the difficulty of absorbing dietary cholesterol, but I believe they take the implications too far. Very little is said about the 20% who hyper-absorb.
Their reasoning is that since dietary cholesterol doesn’t raise serum levels of cholesterol, and because cholesterol was demonized in the first place as the result of a campaign by the sugar industry, there’s nothing to any of the “cholesterol is bad” talk, so eat the shit out of that cholesterol people.
This is bad advice.
Joe proudly tells the audience that he eats 4-6 eggs a day. Throughout the episode, Chris and Joe imply that anyone who doesn’t recognize that cholesterol is fine and healthy is a dummy, then they extend the same logic to saturated fat.
They claim that there is absolutely no reason to limit cholesterol in the diet, ever. Problem is, that is simply not true for about one in four people.
I don’t believe Joe Rogan makes transcripts of his podcast available to the public, and even if he does, I was too lazy to find one, so I typed in the relevant section of the show below.
[Begin informal, but accurate, transcript]
Chris: we get these studies showing that blood cholesterol has no impact on your blood cholesterol for most people.
Joe: say that again, because for a lot of people, they’re like what did he just say (laughing)
Chris: so, even the standard U.S. dietary guidelines, they removed any restriction on dietary cholesterol from U.S. diet guidelines. They basically said there’s no reason to limit cholesterol in your diet anymore.
Joe: now, for people who don’t know why this is so crazy, you need to go to the NY Times article on how the sugar industry bribed scientists so they could blame saturated fat and cholesterol and push the blame away from sugar, think they only got paid 50 grand. Amazing when you think about how many that’s affected.
Chris: (solemn agreement) Yeah, these conflicts of interest are everywhere.
Joe: that’s not conflicts of interest, that’s just crime. Did some horrible things to people.
Then later on…
Joe: so, one more time, dietary cholesterol has no impact.
Chris: yeah, in 70% of people, eating egg yolks and meat, doesn’t do anything to serum cholesterol, the cholesterol in blood. In 30% of people, you’ll get a slight raise in your LDL, so called bad cholesterol, but you’ll also get a small raise in HDL, which means there’s no net clinical impact.
Chris continuing: (referring to the American Heart Association’s decision to remove warnings about dietary cholesterol from our diets) we can’t tell you to remove dietary cholesterol because there is no evidence to support that.
Joe: What took so long?
Chris: Conflicts of interest, status quo (paraphrasing)
Joe: Saturated fat is another one, you talk to the average person, they think you should restrict saturated fat.
Chris: I think there is some nuance here, I think we’re headed to more personalized recommendations depending on goals, health status, genetics, etc.
Joe: I had a conversation with a guy, brilliant guy, and we were talking about eggs, and uh, I said I like to eat 4-6 a day, and he was like “what about the cholesterol? And I was like, wow, you don’t know? Like, you don’t know? You don’t know that and you’re a really smart guy. This is kind of stunning.
Chris: Yeah, think of everything that has to change to reflect that new understanding.
[End informal transcript]
Cholesterol nuance needed…badly
Both sides want it to be so simple.
The Vegans tell you all you ever need is plants.
The Paleo types tell you all their animal products are perfectly safe all the time, so load up on bacon and eggs for breakfast seven days a week.
The truth lies somewhere in the middle, and it’s a sliding scale based on a number of factors, including the state of the microbiome, genetics and factors like uric acid, HbA1c and vegetable oil consumption, all of which oxidize LDL.
High fat diets can do bad things to some people. (R) Where a diet is high in cholesterol, it’s also usually high in saturated fat, and high saturated fat diets are particularly dangerous for certain genotypes, such as APOE4 (which to his credit, Chris briefly touches on in the episode).
But at the end of the day, Joe and Chris are basically saying that dietary cholesterol doesn’t raise serum cholesterol, so let’s load up on all the cholesterol we can get because the people on the other side don’t know a thing about nutrition, their point of view is 100% wrong, and has no merit whatsoever.
Is that likely?
No, it’s not.
Again, I admire Joe and Chris both, and I ate eggs for breakfast today, but I am not nearly so cocky about eggs and cholesterol, and not because I think some dietary cholesterol is necessarily a “bad thing.”
Aaron wrote a great post about how different genotypes process cholesterol and saturated fat differently, which is a must read for anyone looking for a nuanced perspective on this topic. In his post, he echoes some of what Joe and Chris have to say on the issue of cholesterol:
whilst a high level of blood-borne cholesterol is associated with an increased risk of heart disease, most people who suffer from heart disease have normal blood cholesterol levels (7). Secondly, as cholesterol is so fundamental to life it is directly synthesized in the body, mainly in the liver. Excess dietary cholesterol is mainly excreted, and any dietary cholesterol which is absorbed results in a decrease in cholesterol synthesis in the liver (8, 9). Together this means that even a diet very high in cholesterol has little, if any, impact on the cholesterol levels in the blood which are maintained at a steady state.
This statement is true for a good number of people, but there is not a uniform reaction to dietary cholesterol (cholesterol rarely occurs in food without saturated fat alongside) and that needs to be recognized and mentioned when these discussions take place.
Very recent studies have shown the LDL-C increase in response to a high fat diet can range between 5-107%! There is tremendous variability between people.
Back to eggs.
Eggs and the microbiome
Note: for a thorough breakdown of the science behind TMAO metabolism and how genetic factors play a role, Aaron’s recent post TMAO and heart disease: what we know (and what we don’t) is worth a read.
Now on to the way the bugs in our gut handle cholesterol.
Before you start eating 4-6 eggs a day, be aware of a study that appeared in the New England Journal of Medicine (“NEJM”) and a nasty little gut metabolite called trimethylamine-N-oxide, or “TMAO” for short.
The New England Journal of Medicine study found that our gut bacteria metabolize fats, like choline (which is found in abundance in eggs, meat, butter, etc.) into TMAO.
In the NEJM study, when subjects ate eggs while taking a course of antibiotics, TMAO wasn’t produced, but it was under normal circumstances, and guess what?
Elevated TMAO levels are a major predictor of heart disease.
From the Cleveland Clinic Heart Lab:
A new blood test that measures levels of TMAO (trimethylamine-N-oxide) — a metabolite derived from gut bacteria — can powerfully predict future risk for heart attack, stroke, and death in patients who appear otherwise healthy, according to pioneering Cleveland Clinic research.
Ok, so people who are otherwise healthy can still be at risk for heart disease based on consumption of foods that are high in…cholesterol. It’s not necessarily the cholesterol that’s the problem, it’s what the gut does with the cholesterol. Or put another way – it’s what an unhealthy gut does with cholesterol, as eating fish seems to be protective of cardiovascular health although fish is one of the foods highest in TMAO. So, the nuance here is that those with certain unhealthy strains of bad bacteria in their colon will be at greater risk for heart disease when they eat a lot of fish and eggs, whereas someone with a different microbiome might not have as much of an issue.
I had my TMAO levels tested and they were normal, which is a step that should be taken by anyone on a high cholesterol diet as well.
TMAO, when elevated, is associated with a dangerous buildup of plaque in the artery wall, and it’s produced when we eat eggs. In fact, the NEJM study induced production of TMAO by having subjects eat…hard boiled eggs!
To quote the study:
After adjustment for traditional risk factors and other baseline covariates, elevated plasma levels of TMAO remained a significant predictor of the risk of major adverse cardiovascular events.
Based on this NEJM study, you could be eating eggs everyday and thinking you’re fine because your cholesterol looks good (which would make sense because most don’t absorb the cholesterol they eat). All the numbers could be normal, but the whole time you were testing the wrong thing. Those on a high cholesterol diet should be looking more at TMAO levels than at cholesterol levels. Serum cholesterol levels have zero to do with the way our microbiome uses cholesterol rich foods to create TMAO, hence the NEJM study expressly stating: “after adjustment for traditional risk factors…”
My take is this: if you eat foods that are rich in cholesterol, as I sometimes do, know that you gain benefit from these foods, but that they can also cause problems for some when consumed in excess. The authors of the NEJM study do not recommend excluding choline from the diet, they recommend cycling intake so the body has the chance to excrete TMAO.
Again, quoting the NEJM:
Our data suggest that excessive consumption of dietary phosphatidylcholine and choline should be avoided; a vegetarian or high-fiber diet can reduce total choline intake.16 It should also be noted that choline is a semiessential nutrient and should not be completely eliminated from the diet, since this can result in a deficiency state. However, standard dietary recommendations, if adopted, will limit the intake of phosphatidylcholine- and choline-rich foods, since these foods are also typically high in fat and cholesterol content.
The next few days for me will be plant based, low fat days since I had a higher fat day today. The goal is to let my body clear the TMAO.
Eggs and Arachidonic Acid
Besides TMAO and genetic differences in cholesterol absorption, another feature of eggs that is rarely discussed is arachidonic acid, both in the eggs as well as the vegetable oils they are often cooked in. (R) In fact, I would go as far as to say that the likely reason some epidemiological studies in particular find and increased risk of disease in eggs is due to the fact that they are:
- Eggs from factory farms;
- Eggs cooked in vegetable oil
The same people who absorb cholesterol from eggs are also the same people who absorb the rancid vegetable oils the eggs are cooked in! Oxidized phospholipids bind preferentially to some our most dangerous LDL particles, so if these folks also have elevated Lp(a), boom, the perfect storm for heart disease is present.
But vegetable oils aren’t just a problem because of damaged fats, they are also high in linoleic acid, an omega 6 fatty acid that converts to arachodonic acid in the body. Arachodonic acid (ARA) is one the most pro-inflammatory compounds in the human diet. (R) The linoleic acid in vegetable oil converts to ARA, and does so at a stepped up rate in certain FADS1 genotypes, and the eggs are already high in ARA, especially if the hens have been eating a bunch of corn and soy. (R)
This is why if you are going to eat eggs every day, eat eggs from the farmers market that have been eating grass, or at a minimum something other than GMO grain. The diet of the hens dictates just how much ARA is in the eggs you eat, and the less ARA the better.
Key Takeaways – are eggs safe?
In sum, I don’t eat eggs everyday, and that doesn’t make me a dummy, it makes me a guy who reads the New England Journal of Medicine.
The ARA content of eggs and especially factory eggs cooked in vegetable oil shouldn’t be ignored.
So, if you’re going to eat eggs, be smart – no vegetable oil (poaching is fantastic) and get to know your local farmers.
Related supplement note: PQQ came on my radar largely because there is some evidence it may reduce TMAO levels. For more on that, check out my blog post: I took 10mg of PQQ, here’s what happened.
See also: Vegan eggs, are they healthy?