Cholesterol: why "good" and "bad" is an oversimplification
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Many people have been taught to think of cholesterol as either good or bad. LDL is framed as harmful. HDL is framed as protective. Total cholesterol is often treated as the headline number.
This way of thinking is simple, memorable, and incomplete.
It can be useful for broad public health messaging, but it often falls short when someone wants to understand their personal risk or decide what to do next.
This page explains why the good and bad cholesterol story is an oversimplification, and what matters more in practice.
This article is part of our wider ASCVD (heart disease and stroke) resource hub, which brings together all our guidance on cardiovascular prevention in one place.
Cholesterol itself is not the problem
Cholesterol is an essential molecule. Your body uses it to build cell membranes, produce hormones, and support normal brain and nerve function.
Every cell in the body can make cholesterol. The issue is not cholesterol existing in the body, but how cholesterol is transported in the bloodstream and how often blood vessels are exposed to certain transport particles over time.
Cholesterol does not travel alone
Because cholesterol does not dissolve in water, it cannot travel freely in the blood. Instead, it is carried inside transport particles called lipoproteins.
Different lipoproteins behave differently. Some are more likely to contribute to plaque formation in blood vessels. Others are involved in returning excess cholesterol to the liver.
When we talk about cholesterol risk, we are really talking about the behaviour and number of these particles, not the cholesterol molecule itself.
Read more about cholesterol, triglycerides, and transport particles
Why LDL is not the whole story
LDL cholesterol measures how much cholesterol is being carried inside LDL particles. It does not tell us how many particles are carrying that cholesterol.
Two people can have the same LDL cholesterol level but very different numbers of LDL particles. One may have fewer large particles. The other may have many smaller ones.
From a long-term risk perspective, particle number matters more than cholesterol mass alone.
This is one reason some people experience heart disease or stroke despite being told their LDL cholesterol is normal.
What about HDL?
HDL is often described as good cholesterol. In reality, HDL particles are involved in transporting cholesterol away from tissues and back to the liver.
Having very low HDL can be a marker of poor metabolic health. However, having very high HDL does not reliably reduce cardiovascular risk.
Attempts to raise HDL cholesterol with medication have not consistently reduced heart attack or stroke risk. This tells us that HDL cholesterol levels alone do not capture how well these particles function.
In other words, HDL is more complex than simply being good.
What actually predicts risk more reliably
Research over the past two decades has shown that the number of cholesterol-carrying particles capable of contributing to plaque formation is a stronger predictor of cardiovascular risk than LDL cholesterol alone.
These particles all carry a protein called apolipoprotein B, or ApoB. Measuring ApoB provides a direct count of these particles.
Risk is driven by a combination of:
- how many of these particles are present
- how long blood vessels are exposed to them
- the health of the vessel walls themselves
Read more about ApoB and why particle number matters
Where metabolic health fits in
Blood pressure, smoking, inflammation, and metabolic health influence how damaging cholesterol-carrying particles become once they interact with blood vessels.
Poor metabolic health makes particles more likely to become trapped and cause plaque. This does not replace the importance of particle number. It adds to it.
A sensible prevention approach addresses both exposure and vulnerability.
Read more about ASCVD and the full picture of cardiovascular prevention
What to take away
The good and bad cholesterol story is not wrong, but it is incomplete.
The more useful way to think about cholesterol is:
- cholesterol is essential
- cholesterol travels in particles
- some particles are more risky than others
- risk depends on number, time, and vessel health
Understanding this helps explain why standard cholesterol tests can be reassuring but still miss long-term risk.
If you would like a practical summary of how this fits into prevention, you can download our two-page heart attack and stroke prevention guide.