Cholesterol: the building material of your life

An honest, understandable deep dive into the most misunderstood molecule in your body: why you couldn’t live a single day without cholesterol, when it does become unfavourable, and what that means for your eggs, your plate and your protein shake.

Take an egg out of your fridge. Feel how cool and smooth it lies in your hand.

So ordinary. And at the same time a small marvel: packed with building materials. Protein, vitamins, minerals, nature has folded the raw ingredients of a genuinely nourishing little package into it. And one of those building materials carries a name that frightens a lot of people.

Cholesterol.

You know it as a number on a blood test. Something that can be “too high”. Something in the leaflet next to the picture of a narrowed blood vessel. But that isn’t the whole story. It isn’t even half the story.

Because without cholesterol you’d have no brain to read this with. No hormones. No vitamin D. No cell walls holding you together.

This piece is about cholesterol, not as a villain, but as building material. I’ll take you through it step by step, in plain language, from what it is to the newest insights of 2026. And where the science still doubts, you’ll hear it from me.

An egg is full of building materials, cholesterol is one of them

Let’s stay with that egg, because it shows nicely what cholesterol actually is.

An egg is surprisingly complete. It contains a complete protein, meaning: all nine “essential amino acids”, the building blocks for your muscles that your body can’t make itself and must get from food. On top of that, one egg gives you choline (important for your brain and nerves), vitamin D (which few foods are naturally rich in), vitamin B12, selenium, riboflavin, and the pigments lutein and zeaxanthin that protect your eyes. All that for around 70 calories.¹

And yes: there’s cholesterol in it too. Not as contamination, but as building material, exactly as in your own body.

That’s the image to hold on to: cholesterol is building material. Not an intruder, but stock. Everything that follows, the parcels, the factory, the risks, begins with that one truth.

Cholesterol is not fat. And “good” and “bad” don’t really exist

You’ve probably learned: cholesterol is fat, and there’s a good kind and a bad kind. Hold that picture for a moment, we’re going to adjust it together, calmly, step by step.

First: cholesterol is not fat. It’s a sterol, read it as “a sturdy little building block”. It slots between the walls of your cells like the slats in a slatted bed base: it makes your cells supple and firm at the same time. Bendy enough to move, firm enough not to fall apart. Without that little block, a cell would collapse like a limp soap bubble.²

And then that “good” and “bad” cholesterol. Very simply put: it doesn’t exist. There’s only one kind of cholesterol. What differs is the way it travels.

Here comes the image I’ll keep for the rest of this piece. Think of your blood vessels as the roads of your body. Cholesterol is precious cargo that has to travel those roads to the building sites, your cells. But there’s a problem: cholesterol is fatty, and your blood is watery, and fat and water don’t mix (think of a drop of oil in a glass of water). Loose cholesterol would just float and never arrive.

Your body’s solution: it packs the cholesterol into little parcels with a protein coating, so they can travel through your watery blood after all. These parcels are called lipoproteins. Two of them show up most often:

• LDL is the parcel that delivers cargo to your cells, the delivery service.
• HDL is the parcel that collects the surplus and returns it to the liver, the central depot, the pick-up service.

LDL got the nickname “bad”, HDL “good”. But watch out, this is where the leaflet stops and the real science begins: LDL and HDL are not the cholesterol. They’re the parcels that carry it. Calling them good or bad is like calling a delivery parcel good or bad, when it’s really about the cargo and the traffic.

And straight away a crack in the simple story, because that belongs here. “HDL is good, so higher is better” isn’t true. Researchers found people with naturally very high HDL due to a rare gene fault, and they turned out to have more heart trouble, not less.³ In a large study the relationship even turned out to be a U-shape: both very low and very high HDL were linked to less favourable outcomes.^4,5,6 The lesson: it’s not about a high number, but about how well that pick-up service actually works.

Your body is its own cholesterol factory, and that changes everything about your plate

If cholesterol were so dangerous, would your body run a factory for it, day and night? That’s exactly what it does. And this bit turns the whole egg debate on its head.

You make the vast majority of your cholesterol yourself. Your own liver and your intestines are the factory. What you eat supplies only a small part.² In plain language: the cholesterol on your plate is not the boss of the cholesterol in your blood. Your own factory is.

And that factory has a thermostat. Eat more cholesterol, and your body makes less itself. Eat less, and it makes more. It largely regulates itself.² (The main switch of that factory is an enzyme with an ugly name, HMG-CoA reductase, remember it, because it turns out to be exactly where the most famous heart medicines act.)

That’s why the decades-old advice “above all, don’t eat cholesterol” turned out to be far too simple.

What cholesterol is really for

Before we talk about risks, I want to show you how indispensable this building material is. Because only when you grasp how badly you need it do you understand why your body guards it so carefully.

From cholesterol your body builds, among other things:

• your cell membranes, every cell, from your skin to your heart;
• vitamin D, which your skin makes from cholesterol the moment sunlight hits it;
• bile salts, with which you digest the fats in your food;
• your stress hormone cortisol;
• and your sex hormones: testosterone, oestrogen, progesterone.

Read that list again. Fertility, bones, muscles, your mood, your resilience to stress, it all begins with this one building material.

There’s a famous chart that medical students learn by heart: the hormone cascade (officially: steroidogenesis). Cholesterol sits at the top; below it, it branches out like a family tree into all your hormones.⁷

Read from top to bottom. Cholesterol is the source. From it your body first makes pregnenolone, the “mother hormone”, because almost everything springs from it. On the left it becomes progesterone (cycle and pregnancy) and the adrenal hormones cortisol (stress) and aldosterone (blood pressure and salt). On the right run the “male” hormones: DHEA → androstenedione → testosterone → DHT. And from those your body makes (via the enzyme aromatase) the “female” hormones: the oestrogens oestrone, oestradiol and oestriol. Both men and women have them all, just in different proportions. And note: vitamin D and bile salts hang from it too, but don’t run via pregnenolone; those branches leave straight from cholesterol.

Look at that chart once more. One molecule at the top, and a whole family of hormones below it. That’s not a villain. That’s a foundation.

And then your brain. About a quarter of all the cholesterol in your body sits in your brain, while your brain is only around 2% of your weight. The brain researchers Ingemar Björkhem and Steve Meaney described so aptly how your brain makes its own cholesterol on the spot and uses it as insulation to coat your nerves, your myelin, so that thoughts can travel at lightning speed.⁸ Very simply: cholesterol is the rubber around the electrical wires of your head.

And the nuance belongs right here. Your brain makes that supply itself, behind the blood-brain barrier, almost entirely cut off from the cholesterol travelling through your blood.⁸ That is awkward for the simple story: you cannot eat your brain smarter with cholesterol on your plate. What you eat does not determine what your brain builds.

Building material, you’d say now. And you’d be right. But there’s a shadow to it, and it doesn’t begin with the cholesterol itself.

So when does it become unfavourable? It’s not a fat problem, but a damage problem

If cholesterol is so useful, why does it have such a bad name? Here we have to be precise, because this is exactly where the folk story goes wrong, and I want to wake you up, not scare you.

The picture of “cholesterol that scales up like limescale in a pipe” is too simple. Back to our roads. A healthy vessel wall is like smooth, well-maintained road surface. A problem only arises when that surface gets damaged and rough.

1. The inside of a blood vessel gets damaged, by smoking, high blood pressure, high blood sugar, long-term inflammation. The smooth road surface turns rough.
2. On that rough spot, LDL parcels snag and slip into the wall.
3. There their cargo becomes oxidised, damaged, a bit like rust.
4. Your immune system sees that rusted cargo as an intruder and sends clean-up cells. They gorge themselves and pile up into a thickening in the wall: a plaque, like a bump in the asphalt.
5. That bump narrows the passage and stiffens the surface. And that’s unfavourable for your heart and vessels.

See the difference? It’s not so much about how much cholesterol you have, but whether the road surface is damaged and inflamed, and whether the parcels get stuck there and start to “rust”. Cholesterol got the blame, while the real culprits are often elsewhere: inflammation, smoking, high blood pressure, high blood sugar.

How sure are we that inflammation plays along? In the large CANTOS study, heart patients received a medicine that only dampened inflammation and did nothing to cholesterol. Their outcomes still improved.⁹ That was the proof: inflammation is a player of its own, not a bystander.

And here lies the hope right away: almost all of those damage factors are ones you can influence yourself. More on that shortly.

Why doctors now count the number of parcels: ApoB and Lp(a)

If it isn’t only about the amount of cholesterol, what do doctors look at nowadays? This is where the field is shifting right now, and I want you ahead of the leaflet.

Every risk parcel, every LDL-type particle, carries exactly one marker protein on its outside: ApoB. Count the ApoB, and you’re essentially counting the number of parcels bumping against your road surface. And that number sometimes matters more than the total cargo they carry together. In plain language: it’s not how much cholesterol is driving around in total that counts, but how many separate parcels knock against your vessel wall. Many small ones can be more unfavourable than a few full ones. ApoB is now regarded as a more accurate measure of that risk than the classic LDL number alone.¹⁰

And then there’s Lp(a), say it as “L-P-little-a”. This is a largely inherited variant, which you can do little about with lifestyle. About one in five people has a raised Lp(a) and doesn’t know it, because it’s rarely on the standard test. In the updated European guideline of 2025, Lp(a) was elevated to a factor that should be measured at least once in life in every adult.¹¹ Do you have early heart problems in the family? Then this is the number to ask about.

Remember: it’s about the number of parcels and the state of the road, not one single figure.

And then your plate: what’s really unfavourable?

You now understand the building material, the factory, the parcels and the roads. So we can finally answer the question that probably brought you here: what should I actually eat?

First an honest correction, because it’s often asked this way: “which food contains a lot of bad cholesterol?” Very simply: none. Bad cholesterol doesn’t exist in food, “bad” referred to a parcel (LDL) in your blood, not an ingredient in the supermarket. What your food does do is influence your own factory and your road surface.

And then it turns out: the cholesterol in your food isn’t the big culprit, three other things are.

Saturated fat and trans fat. This raises your LDL far more than cholesterol from food. Think of lots of butter, fatty meat, large amounts of full-fat dairy, and above all industrial trans fat. Replace some of that saturated fat with unsaturated fat, olive oil, nuts, oily fish, and your LDL drops measurably.

And here it gets more nuanced. In a review of fifteen randomised trials, together more than 56,000 participants, eating less saturated fat lowered the number of heart and vascular events by about a sixth. On mortality there was barely any effect.¹² So less saturated fat helps, but it is no miracle cure, and that difference is rarely what you hear in an advert.

Ultra-processed food. This is what I’d call “today’s food” to really watch out for. Biscuits, crisps, ready meals, soft drinks, quick snacks: rich in energy, saturated and trans fat, poor in fibre. They feed excess weight, a disturbed blood sugar, a fatty liver and inflammation, exactly the rough road surface where the parcels get stuck.

Overeating. Structurally eating more than you use is perhaps the quietest culprit of all. Excess weight around the belly drives up your triglycerides (your blood fats), lowers your HDL and feeds the inflammation in your vessel wall. Not one meal, but the sum, day after day.

See what happens? The spotlight shifts from that one egg to your whole pattern. And that’s good news, because a pattern is something you can steer.

How many eggs may you really have?

I made you wait for the egg on purpose, because without the story above the answer would put you on the wrong foot.

One large egg contains about 186 milligrams of cholesterol, all of it in the yolk.¹ For years that was enough to banish it. But remember the thermostat? Eat more eggs, and your body squeezes its own production shut.²

In a study among healthy young adults, participants went up to three eggs a day. The ratio between their parcels, the LDL/HDL ratio, did not get worse. It even shifted slightly in their favour.¹³ In a second study, with two eggs a day compared against a porridge breakfast, that same ratio stayed the same as well.¹⁴

And don’t forget what else is in that egg: that complete list from earlier, protein with all the building blocks, choline for your brain, vitamin D, B12, selenium. An egg is not a “cholesterol bomb”; it’s one of the most nourishing things in your fridge.

So: is it unfavourable to eat a lot of eggs? For most healthy people the honest answer is: no. About one egg a day fits fine into a healthy pattern. Below roughly one egg a day, science finds hardly any sign of harm.

But here too I’ll show you the cracks:

• The studies contradict each other. Some large studies see a slightly less favourable picture above one egg a day; others see no link at all with heart and vascular disease. They’re also mostly observational studies, they see association, not cause. And people who eat lots of eggs often eat them alongside bacon and white bread. Then the question is: was it the egg, or what lay next to it?
• The two egg studies above are also small and short, with a few dozen healthy young participants. That is something other than evidence for everyone.
• Some people are hyper-responders: in them, blood cholesterol does rise clearly from cholesterol in food. They usually don’t know it, until a blood test shows it.¹⁵
• For people with diabetes or the inherited condition familial hypercholesterolaemia it’s different. In them, several studies do point to a less favourable picture with a lot of eggs. For them the rule is: talk to your doctor, not to a blog.¹⁵

In plain language: for most people the egg is fine. The question isn’t “egg or no egg”, but “what lies next to the egg, and how does your body respond to it?”

The gym generation and the egg mountain

Maybe you recognise it: the gym generation knocks back eggs by the dozen, alongside shakes, bars and powders. Justified?

For the egg itself: largely yes, and the gain lies precisely in the yolk everyone is afraid of. In a lovely experiment, young men ate either whole eggs or only the white after strength training, with exactly the same amount of protein in each. The whole eggs boosted muscle building clearly more strongly.¹⁶ The yolk, with its fats, cholesterol and micronutrients, turned out to be no ballast, but the engine. It did involve ten trained young men, so keep it modest.

But mind the context, because here the spotlight shifts again. A trained, young body usually copes fine with a few eggs a day; the thermostat plays along. The downside rarely sits in the egg and far more often in the rest of the shelf: some sports nutrition is ultra-processed, bars and powders full of saturated fat, sugars and additives. And “getting a lot of protein” isn’t the same as “needing a lot of eggs”. Anyone who trains hard and falls into a risk group (diabetes, familial high cholesterol, high Lp(a)) does well not to go by feel, but to let their blood show once a year what their body makes of it.

Eating consciously isn’t the same as eating fearfully. It’s eating with your eyes open.

The pills and where the story began

One thread I want to finish with, because you hear so much about it: the medicines. And their origin deserves a moment.

It began with detective work. Ancel Keys, with his Seven Countries Study, laid down a link between cholesterol and heart trouble; the famous Framingham study showed that your cholesterol today predicts something about your heart later. And in 1972 the Japanese researcher Akira Endo, after screening thousands of moulds, found a substance that could turn down exactly that factory switch from the start of this piece, HMG-CoA reductase. The first statin was born, harvested from a blue-green mould.¹⁷

The main medicines, brief and honest, in plain language:

• Statins squeeze the cholesterol factory in the liver a bit shut. Cheap, well studied, and valuable for those at raised risk. Muscle complaints occur, but less often than the stories suggest, part is the nocebo effect (complaints because you expect them).
• Ezetimibe blocks the uptake of cholesterol in the gut.
• PCSK9 inhibitors (injections) make your liver fish more LDL parcels out of the blood.
• Inclisiran is smarter still: it switches off the blueprint for the PCSK9 protein, halves the LDL, and needs injecting only twice a year.
• Bempedoic acid acts on the same route as a statin, but only becomes active inside the liver, which gives fewer muscle complaints.

Are statins “poison”, as you read online? No. Are they needed by everyone? Also no. The answer depends on your risk, and that conversation belongs in the consulting room, not on the internet.

This article is not medical advice. It doesn’t replace a blood test, a GP, or your treating specialist. Use it to ask better questions, not to make decisions.

Friend or foe? The question itself is wrong

We’re back at the beginning, with that egg in your hand.

Cholesterol is not your enemy. It’s building material, the stock from which you build your brain, your hormones and your cell walls. Your body makes it on purpose, every day, because it can’t do without.

It only becomes unfavourable in combination, when the road surface gets damaged, when too many parcels circulate, when inflammation and excess weight and smoking and a disturbed blood sugar wreck the place. And almost all of those factors you can influence. Not with fear of one little egg, but with a pattern: moving, less ultra-processed food, not structurally overeating, not smoking, and when in doubt, letting your blood speak.

Because most of the power lies not in the pill and not in the leaflet. It lies in the pattern you begin today.

So not: “may I have this egg?” But: which building materials are you giving, meal after meal, to the body you’ll live in for the rest of your life?

Related reading

• The liver, quiet workhorse
• The omega alphabet
• Olive oil: liquid gold or marketing?
• The body is not a calculator

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If in doubt or for personal questions: discuss your blood results with your GP or treating specialist.

Sources on this site are cited in APA style, with a DOI wherever one exists. Why I made that choice →