Cholesterol Can Severely Impair Cognitive Function
Learn How This Happens & Why You Should Care
It should be pretty obvious to everybody now; lower cholesterol means better health and a longer lifespan.
We have been barraged over the last 3 decades with the same message: cholesterol bad.
Over the last, say, 5 years, that message became more refined: some cholesterol good, some cholesterol very bad.
Cardiovascular experts, public health bodies, and clinical researchers all seem to be in agreement on this.
It is observed as medical fact that dietary cholesterol increases serum cholesterol, and that serum cholesterol is a serious risk factor for heart disease (among other diseases).
Surprisingly, though, there are a large number of people (mostly on YouTube and bodybuilding blogs) who claim that cholesterol is not damaging to health at all.
They claim a number of things, such as “dietary cholesterol is not linked to cholesterol levels in the blood”, and “high cholesterol is fine, sugar is the real issue”.
We think there are a few reasons why people make these claims; financial, denial, the need to tell people something different to gain an audience, supplement industry pressure, to name just a few.
We will deal with this issue below.
However, the main purpose of this article is not to discuss the overall health impact of cholesterol.
No, we’re going to talk about something that does not get anywhere near as much attention as cholesterol’s impact on heart health.
We’re going to look at how cholesterol affects the long-term health of your brain.
We’ll discuss the relationship between your brain and cholesterol, how much cholesterol you really need, whether your body can make enough to support optimal brain health, and so on.
We’ll also look at how your cholesterol intake, and therefore your serum cholesterol levels, influences your day-to-day cognitive function.
Does cholesterol affect your memory?
Does it reduce focus?
Does your brain need cholesterol?
Is cholesterol intake linked with dementia and Alzheimer’s in any way?
Should you reduce your cholesterol intake for better brain health?
We will touch on all of these questions in the article below. We urge you to read this article carefully and to let us know if you have any questions at all on the subject of cholesterol, brain health, and cognitive function. If you have any uncertainty about cholesterol and heart health, we suggest you focus your reading on bodies of medical professionals and not YouTube bloggers.
We Do Need Cholesterol, But We Don’t Need To Eat It
You will hear this every time you read about this subject online, so let’s get it out the way.
Your body and your brain need cholesterol.
Without cholesterol, you couldn’t complete a number of literally vital bodily functions.
You couldn’t make important hormones like testosterone (made in part from cholesterol).
You couldn’t produce the cell membranes which enclose every cell in your body.
You couldn’t produce enough bile, which is necessary for the breakdown of dietary fats in the stomach.
Without cholesterol, you really wouldn’t last very long.
However, some people mistakenly take this as meaning that you need to consume some amount of cholesterol from your diet.
That is absolutely not the case.
Like with most genuinely VITAL substances in the human body, you are quite capable of making all the cholesterol you need yourself from its constituent parts.
Cholesterol is synthesized in the liver from acetyl coenzyme A, or acetyl-CoA. This peptide is involved in the synthesis of many different lipids.
The process which results in cholesterol being formed is a long and complex one, but the liver makes short work of it.
Thanks to the liver’s efficiency, you are more than capable of producing all the cholesterol you need for the bodily functions laid out above.
There is absolutely no reason why any healthy person should need to augment their own production of cholesterol with dietary cholesterol.
This is true for most substances that your body really needs to survive (excluding things like water and oxygen of course).
After all, it would be a pretty big evolutionary disadvantage if we needed to source every individual molecule we needed for survival from the environment.
Cholesterol Intake DOES Influence Serum Cholesterol
There is a major trend at the minute of fitness YouTubers, bloggers, and so-called “experts” telling people that there is no link between dietary cholesterol intake and serum cholesterol levels.
That simply isn’t true.
There is a direct, causal link between dietary cholesterol intake and serum cholesterol levels.
Not only are these weekend physicians wrong, but in most cases they are purposefully lying to you.
We don’t want this point to hijack the article, so we’ll very quickly establish that dietary cholesterol DOES influence serum cholesterol, and then highlight some reasons why we think these internet experts might be lying to you.
It shouldn’t take a lot of effort for you to understand that dietary cholesterol intake increases serum cholesterol.
When you consume things that the body has uses for and can be absorbed, they tend to end up in the blood.
If you eat salt, your serum sodium levels go up.
If you eat fat, your serum fat levels go up.
And if you eat cholesterol, your serum cholesterol levels go up.
Take a look at this extensive meta-analysis which examined hundreds of studies on the relationship between dietary cholesterol and serum cholesterol.
As the lead author stated quite clearly, this meta-analysis showed that: “Serum cholesterol concentration is clearly increased by added dietary cholesterol“.
Here we have another study looking at egg yolk consumption and serum cholesterol. Again, we have a very clear increase in serum cholesterol from increased cholesterol intake.
So why are there people saying that eating cholesterol doesn’t affect cholesterol levels?
Well, usually they justify their claims by appealing to a handful of studies which they claim prove them right.
Take a look at this article from the incredibly qualified Acupuncturist Chris Kresser, which is often used to justify eating 10 egg yolks per day.
Here, acupuncture wizard Chris talks about some studies monitoring egg consumption: “There have been very well controlled egg-feeding studies where they didn’t change anything else in the diet but they added two to four eggs per day to the diet and then measured people’s serum cholesterol levels, and in 70% of people, there was no discernible change at all. They ate four additional egg yolks a day, and their cholesterol didn’t go up and it didn’t go down. “
Chris goes on to say: “In other words, eating cholesterol isn’t going to give you a heart attack. ” Quite a bold claim, but he did study acupuncture, so he obviously isn’t just pulling this out of thin air.
So how can that be?!
Which study is right?
Who are you to believe?
Well, if you look at the meta-analysis we linked first, you’ll see that these kinds of studies are very easily explained away: “Serum cholesterol concentration is clearly increased by added dietary cholesterol but the magnitude of predicted change is modulated by baseline dietary cholesterol.”
The study goes on to state that the biggest change will be seen in people with cholesterol levels near minimum, while you can expect to see no change at all in people with a cholesterol level of 400-500mg/dl.
It continues to then outline a range of factors which MIGHT cause someone to have higher cholesterol levels than another person with the same diet.
Take a look at the meta-analysis Chris Kresser is pulling his data from. If you trudge through this paper, you’ll see that the researchers largely found there to be a statistically significant association between cholesterol intake and serum cholesterol levels:
“In conclusion, the effect of dietary cholesterol on incident CAD and serum cholesterol outcomes remains unclear. Intervention trials showed a statistically significant increase in total, LDL, and HDL cholesterol when comparing intervention doses of 500–900 mg/d dietary cholesterol with control doses”.
There is another gem in there towards the end:
“The relation between dietary cholesterol and serum cholesterol has been estimated to be linear with cholesterol intake up to 600 mg/d. Studies have reported a nonlinear relation for intakes of cholesterol .600 mg/d, with little effect on serum lipid concentration in most people (59). The findings from our meta-analysis indicate that increases in serum cholesterol are no longer statistically significant when dietary cholesterol interventions exceed 900 mg/d, which is consistent with previous observations showing a plateau in serum cholesterol concentrations when dietary cholesterol increases (60).”
Starting to get it?
Dietary cholesterol doesn’t influence serum cholesterol levels if they are already very high.
The higher your baseline serum cholesterol levels, the smaller the increase you will see from eating more cholesterol.
If you have very low blood cholesterol levels, dietary cholesterol will have an enormous impact.
Studies looking at populations who already consume very large amounts of cholesterol will invariably fail to see a difference from eating more cholesterol; this is the problem of the sick population.
As Geoffrey Rose put it in his brilliant 2001 paper Sick Individuals and Sick Populations, “If exposure to a necessary agent is homogeneous within a population, then case/control and cohort methods will fail to detect it: they will only identify markers of susceptibility.”
So what constitutes a low cholesterol level? Are we really dealing with a sick population?
Well, let’s avoid quacks and let the major public associations guide us.
According to the Center for Disease Control & Prevention in the US, mean cholesterol levels for adults aged 20 and over was 192mg/dl.
They state that 12% of he US population aged 20 and over has “high” cholesterol levels, which they class as above 250mg/dl.
In 2011-12, “78 million U.S. adults (nearly 37%) had low-density lipoprotein cholesterol levels that fall in the range where experts recommend cholesterol medicine or had other health conditions putting them at high risk for heart disease and stroke.”
According to heart experts, atherosclerosis pretty much cannot occur when cholesterol levels are below about 70mg/dl. To us, that would be a healthy cholesterol levels; one that lets you build all the testosterone you need without causing plaque build-up in your arteries.
The next time you see some YouTube shill telling you that they ate 6 eggs per day and their cholesterol didn’t go up, take a look at their cholesterol levels.
More often than not, you’ll see young men with cholesterol levels above 250mg/dl when they started their “experiment”, meaning that they were ALREADY at risk of developing heart disease and stroke.
Cholesterol Does Affect Heart Health
Since this is a site dedicated to cognitive performance, we aren’t going to spend too long dwelling on cholesterol’s effect on health.
We think the evidence here is abundant and readily available. You can easily do this research yourself.
However, since there is so much misinformation out there, we think it is worth going over it briefly.
Every major body of surgeons and cardiovascular specialists state that cholesterol is a significant risk factor for heart disease.
In fact, according to this paper, cholesterol is the only necessary risk factor for the development of atherosclerosis (where you get a fatty plaque build up on the inside of your arteries). Atherosclerosis is a major cause of heart disease, so preventing atherosclerosis is a good way to significantly reduce the risk of developing heart disease.
The link between atherosclerosis and heart attack or stroke is not difficult to establish.
Atherosclerosis is technically classed as a disease. it is where a hard plaque builds up on the inside of your arteries.
This plaque forms when high levels of cholesterol stick to your artery wall, and bind with calcium, different forms of fat, and other substances found in the blood. This sticky, calciated substance grows and hardens over time.
This plaque effectively narrows the passage through which blood can flow. It also makes blockages significantly more likely.
Atherosclerosis can develop in any artery in the body.
This means that it can cause a variety of extremely serious, often fatal conditions.
For example, atherosclerosis in a coronary artery, which deliver blood to the heart, can be lethal.
A build up of plaque in a coronary artery will severely reduce blood flow to the heart. This means a section of your heart will stop receiving blood, and will become damaged as a result. If there is one muscle in your body you do not want to atrophy, it is your heart muscles!
Should the passage become restricted enough, a blockage becomes extremely likely.
A blockage in a coronary artery will cause an acute, life-threatening heart attack.
Similarly, you can get atherosclerosis in your carotid arteries, which take oxygen-rich blood from your heart to your brain.
Restricting blood flow in these arteries is really not a good idea.
Should either of these arteries (which are on either side of your neck) become severely restricted or totally blocked, you will experience a stroke.
If blood gets sufficiently restricted, regions of your brain will not be getting all the oxygen and nutrients they need to survive, let alone thrive.
This brings us neatly onto the main sections of this article: the relationship between your brain and cholesterol.
Cholesterol & Your Brain
Contrary to what many people may think, cholesterol does not just affect your cardiovascular health.
Cholesterol can also influence your brain health and your cognitive function (which are obviously linked).
There are several ways it affects your cognition.
First and most straightforward is the restriction of blood flow to the brain (mentioned above).
This is an easy chain of events to digest:
- High cholesterol levels cause atherosclerosis
- Atherosclerosis can restrict blood flow in the arteries which feed the brain
- Reduced blood flow means the brain will not be getting all the oxygen and nutrients it needs to function properly
- Some cells may die and areas of the brain may atrophy as a result
- Aspects of cognition that these areas are responsible for will decline
That should be enough to convince you that cholesterol can be pretty devastating to your cognitive function.
There aren’t many things more damaging to your mental functioning than a stroke.
So if you’re interested at all in safeguarding your long term mental capacity and brain health, not to mention your life, cholesterol needs to be taken seriously.
But we can get a lot more specific here.
The link between a high cholesterol intake, or more accurately high serum cholesterol levels, has been firmly established through numerous large-scale clinical trials.
Cholesterol has been found to have a significant impact on specific aspects of cognitive function.
It seems increasingly clear that vascular health has an enormous influence on things like memory, attention, and even mood.
This article discusses how researchers from Leiden University Medical Center in the Netherlands found Low Density Lipoprotein (the “bad” cholesterol”) to have a serious affect on reaction times.
The researchers studied people using statin drugs (which lower LDL cholesterol), and found a correlation between LDL level variance and cognitive impairment.
Basically, the more someone’s LDL levels fluctuated, the longer they took to respond in reaction time tests.
Another study, using elderly women as their subjects, looked at LDL cholesterol levels and a range of cognitive functions, including memory, focus, and linguistic abilities.
According to study lead author Kristine Yaffe, MD, UCSF: “”The higher cholesterol these women had, the worse they did on cognitive testing. And using statins, which reduce cholesterol, seemed to be beneficial to their performance on these tests.”
The results showed that there was a direct relationship between LDL cholesterol levels and cognitive performance. Basically, the higher the LDL levels, the worse the test scores. Total cholesterol levels also showed a correlation, but it seems that LDL cholesterol levels had by far the biggest impact on cognitive function.
Clearly, high LDL cholesterol levels have a negative effect on cognitive function; from memory and focus to reaction time and mood, everything seems sensitive to cholesterol levels, and LDL cholesterol in particular.
Cholesterol & Age Related Cognitive Decline
This is where things get a little messier.
We’ll start off by stating that high cholesterol levels in the blood is a significant risk factor for Alzheimer’s disease.
This isn’t just speculation, this is reported in the medical literature with great certainty. Specifically, it is routinely noted that “Elevated extracellular brain levels of LDL cholesterol (i.e. >100 mg/dL) increase AD risk by increasing Aß42 production.” (ref).
Indeed, most medical professionals seem to be in agreement that cholesterol levels, specifically LDL, seems to be a statistically meaningful risk factor for Alzheimer’s disease.
However, there are a number of studies which present a very different picture.
Some research now suggests that low cholesterol levels in very old age is correlated with increased risk of dmeentia and Alzheimer’s.
For instance, check this study out. It was first published in the Journal of Alzheimer’s Disease in 2012.
The researchers here found that, “when measured in midlife, high cholesterol levels associate with an increased risk of late-life dementia and cognitive decline. However, when measured in late-life, high cholesterol levels show no association with cognitive function, or even show an inverse relation.”
That really is interesting. The study goes on to say that “In conclusion, cholesterol associates with late-life cognitive function, but the association is strongly age-dependent.”
It seems that up until a certain age, cholesterol exacerbates cognitive decline.
But then above a certain age, it is preventative somewhat.
These same effects were observed in a different study, looking at people from South Korea aged 65 and over.
These clinical researchers concluded: “Lower serum cholesterol level was associated with worse cognitive function in the community sample. Associations with dementia were specific to AD rather than other subtypes. No cross-sectional association was found between cholesterol levels and cognitive function in AD groups from either sample.”
Obviously, the link here has not been firmly established, nor have we seen a strong mechanistic study explaining how this is supposed to work. But this is a space that requires more research, and it gives us serious food for thought.
For the time being, we think it is wise to simply follow prevailing medical opinion.
It may feel clever to listen to experts that the “doctors don’t want you to know about”; the renegades whispering the secrets of long life to you through their home vlogs,. But these people often have hidden agendas and ulterior motives for telling you what they do.
Try to eat a diet conducive to lower cholesterol levels, especially LDL cholesterol, and get plenty of Omega 3 fatty acids.
DHA is easily the most important Omega 3 fatty acid for long-term brain health and cognitive function.
However, if you get lots of Omega 3s from nuts, seeds, fish, and leafy green vegetables, you will be able to make more than enough DHA.