Beyond Good and Bad: The Real Story of Cholesterol and Your Heart Health

Table of Contents

• Key Points
• Background: The Traditional View of Cholesterol
• Why Cholesterol Matters to Your Body
• The Lipoprotein Ecosystem: More Than Just LDL and HDL
• Key Findings: LDL Is Not the Only Dangerous Particle
• Lipoprotein(a): The Hidden Risk Factor
• Remnant Particles: Another Unmeasured Danger
• A Better Way to Measure Risk: Counting ApoB Particles
• The HDL Mystery: When "Good" Cholesterol Turns Bad
• Investigating HDL Proteins: The League of Shadows
• Clinical Implications: What This Means for Patients
• Study Limitations: What Scientists Still Don't Know
• Recommendations for Patients
• Frequently Asked Questions
• Source Information

Key Points

• Standard cholesterol tests miss Lp(a) and remnant particles, which are dangerous and affect many people.
• ApoB testing counts dangerous particles and is endorsed by European cardiologists, but not yet routine.
• Very high HDL cholesterol, found in 3-10% of people, may be linked to several serious diseases.
• About 20% of people have high Lp(a), which cannot be lowered by diet or exercise.
• A normal LDL reading can falsely reassure people with high apoB levels, raising heart risk.

Background: The Traditional View of Cholesterol

Once upon a time, cholesterol was simple. Medical experts proclaimed that this molecule came in two varieties: an artery-clogging "bad" sort and an artery-clearing "good" sort. The difference between the two was never in the cholesterol molecules themselves, but rather in the way they are packaged for transport through the bloodstream.

These packages take the form of tiny nanoparticles called low-density lipoproteins (LDLs) and high-density lipoproteins (HDLs). LDL particles deliver cholesterol to cells that need it, while HDL particles collect excess cholesterol and carry it back to the liver for disposal.

The public-health message was clear, and generations of patients followed it faithfully: minimize "bad" LDL cholesterol by cutting down on fatty foods, red meat, and dairy products. Increase "good" HDL by exercising more and eating more fruits and vegetables.

This message matters enormously because of the numbers behind it. Approximately one-third of heart attacks and one-fifth of strokes are blamed on having too much LDL cholesterol, too little HDL cholesterol, or both. Since the 1990s, effective medications have been widely available. Statins, for example, work by boosting the liver's ability to clear LDL from the bloodstream.

But a new picture of cholesterol has been emerging in recent years, thanks to several strands of research conducted over the past two decades. Medical guidelines are now being rewritten to better reflect who is truly at greatest risk of heart disease. The standard measure of "bad" cholesterol, it turns out, fails to account for its riskiest form — an extra-bad type that also resists the usual treatments.

Why Cholesterol Matters to Your Body

Before diving into the new findings, it helps to understand why cholesterol is so important in the first place. Cholesterol is far from being purely harmful — it is an essential biochemical that your body cannot function without.

Cholesterol is a key component of cell membranes, giving them structure and flexibility. It is particularly abundant in the fatty sheaths that insulate nerve cells, which explains why an estimated 25% of the body's cholesterol is found in the brain. Cholesterol also serves as a precursor molecule for vital hormones, including estrogen (oestrogen) and testosterone.

Cholesterol becomes troublesome only when it accumulates in the walls of arteries. There, it provokes the formation of structures called plaques. These plaques can rupture and create blood clots that block arteries, leading to heart attacks and strokes.

The Lipoprotein Ecosystem: More Than Just LDL and HDL

Scientists now understand that LDL and HDL are only part of a much bigger system. In fact, researchers describe it as a whole lipoprotein ecosystem — and as in any real ecosystem, the various inhabitants have different roles and different levels of danger.

Besides cholesterol, lipoprotein particles contain various fats, proteins, and other molecules. Working together, they shuttle cholesterol between the cells that use it and the liver, where it is manufactured.

• LDL particles deliver their cholesterol cargo to cells in need of supply, then return to the liver for disposal.
• HDL particles collect cholesterol that is surplus to needs — mopping up cholesterol from dead cells, for example — and carry it back to the liver.
• Together, LDLs and HDLs account for 80-90% of the cholesterol in circulation.

Plaque formation happens when this finely tuned system gets out of balance. The prevailing theory holds that when there is too much LDL cholesterol in the bloodstream, it gets deposited into arterial walls faster than HDLs can clear it away. When this imbalance is aggravated by high blood pressure or chronic inflammation, the result is serious trouble.

Key Findings: LDL Is Not the Only Dangerous Particle

The notion that too much LDL cholesterol is bad for you has solid, decades-old evidence behind it. For one thing, statins and other medications that lower LDL cholesterol demonstrably reduce the rate of heart attacks. Genetics provide even more dramatic proof: a specific genetic variant carried by 1 in 250 people blocks the liver from clearing LDLs and is linked to a 20-fold increased risk of developing heart disease, often before middle age.

However, researchers have discovered that LDL is not the only harmful particle in the bloodstream. Two additional types of dangerous particles — lipoprotein(a) and remnant particles — are not measured in standard cholesterol tests and may be putting millions of people at risk without their knowledge.

Lipoprotein(a): The Hidden Risk Factor

Around one-fifth of people (approximately 20%) carry a genetic variant that causes their bodies to make a troublesome protein called apolipoprotein(a). This protein attaches itself to standard LDL particles, creating a novel particle known as lipoprotein(a), or Lp(a) for short.

The danger is substantial. People with high levels of Lp(a) particles are several times more likely to develop premature heart disease than those with little or none of them. This risk applies to younger people as well as older adults — "premature" heart disease means it strikes before the age most people expect.

Perhaps most worrying is that these high-risk patients often pass standard cholesterol checkups with flying colors. That's because routine tests do not look for Lp(a) at all.

There is more bad news: Lp(a) levels are completely impervious to changes in diet or lifestyle. No amount of healthy eating or exercise will lower them. However, the article notes that drugs from Amgen, Eli Lilly, and Novartis are on the horizon, raising hopes that targeted treatments may soon be available.

Remnant Particles: Another Unmeasured Danger

A second type of dangerous particle that escapes standard testing is called a remnant. These are leftovers of large lipoproteins such as chylomicrons — particles that carry fats from the food you eat. Once these large lipoproteins have delivered their cargo of other molecules, what remains are remnant particles.

Remnants are formidable threats for several reasons:

• They typically carry several times more cholesterol than an ordinary LDL particle.
• Although remnants are larger than LDLs — which in theory should make it harder for them to penetrate the protective lining of arterial walls — the proteins and fats on their surfaces can do serious damage on their own.
• On a per-particle basis, remnants are up to four times more likely to cause heart disease than LDLs.

A Better Way to Measure Risk: Counting ApoB Particles

The revelations about remnants and Lp(a) have led scientists to rethink what actually causes cholesterol-related harm. The problem may not be too much cholesterol cargo, but rather too many LDL particles themselves. It turns out that lipoproteins which tend to get stuck and spill their cholesterol into the artery wall do so because of a protein on their surface called apolipoprotein-B (apoB).

Conveniently, each dangerous particle is wrapped in a single strand of apoB. This means that counting apoB is equivalent to counting the number of potentially dangerous particles in the bloodstream — a much more precise way of assessing heart risk than measuring total cholesterol content.

The European Society of Cardiology now endorses this apoB method as a superior way to measure risk to the heart. However, this approach has not yet been incorporated into the risk calculators used by most doctors in Europe and America.

And the difference matters — dramatically. Research shows that some 20-30% of people have low LDL-cholesterol but also high apoB levels. These individuals are falsely reassured by typical checkups that show "normal" cholesterol, when in fact their particle count puts them at significantly elevated risk.

The HDL Mystery: When "Good" Cholesterol Turns Bad

The traditional story also fails to capture the complexities of "good" HDL cholesterol. In 2012, a research team led by Sekar Kathiresan of Harvard Medical School reported a surprising result: people with genetic variants that raise their HDL-cholesterol levels did not have lower rates of heart attacks. This finding challenged the entire "good cholesterol" narrative.

Today, researchers understand that both low and very high HDL-cholesterol levels are signs of trouble. The mid-range levels found in the majority of people are considered healthy. This means the relationship between HDL and health is U-shaped rather than linear — too little is bad, but so is too much.

Scientists have proposed several explanations for why low HDL might signal danger:

• Relatively low HDL-cholesterol could reflect underlying metabolic conditions such as diabetes, which itself comes with high numbers of remnant particles — and all the risks associated with them.
• Alcohol consumption raises HDL-cholesterol, which means some cases of very high HDL could actually be caused by heavy drinking (a behavior people tend to underreport in studies).

But even accounting for alcohol, a mystery remains. HDL carries out many jobs in the body; it picks up some bacterial toxins, for example. One leading guess is that HDL particles which are stuffed full of cholesterol become dysfunctional — they stop working properly and contribute to disease instead of protecting against it.

The observational evidence is sobering. Very high HDL-cholesterol — at the levels found in 3-10% of people — has been implicated in a strikingly wide range of conditions:

• Diabetes
• Non-alcoholic fatty-liver disease
• Chronic kidney disease
• Age-related macular degeneration
• Alzheimer's disease
• Cancer

Some scientists now believe that dysfunctional HDL may in fact be just as harmful as LDL cholesterol.

Investigating HDL Proteins: The League of Shadows

Researchers have been investigating whether faulty proteins on the surface of HDL particles could identify the dysfunctional ones. Many HDL surface proteins are known to be beneficial. For example, they can block harmful enzymes, support the body's immune system, and manage early responses to injury or infection.

Scientists believe HDL may also protect blood vessels through a variety of mechanisms:

• Fighting inflammation
• Preventing artery damage
• Supporting tissue repair
• Reducing blood clots
• Helping control immune responses and metabolism

None of these functions has much to do with how much cholesterol the HDL particles carry — which helps explain why measuring HDL cholesterol alone gives an incomplete picture.

The sheer complexity of HDL is staggering. All told, some 280 proteins and counting are thought to be part of HDL particles. But identifying which proteins sit on the more dangerous HDL particles is extremely difficult, because each individual HDL particle carries only a small subset of two or three of these proteins.

Clinical Implications: What This Means for Patients

These discoveries have profound implications for how heart disease risk is assessed and managed. The traditional cholesterol test, which measures LDL and HDL cholesterol levels, is simply not capturing the complete picture of cardiovascular risk.

The key takeaways for patients are:

1. Standard tests can give false reassurance. Approximately 20-30% of people have low LDL-cholesterol but high apoB levels, meaning their particle count puts them at risk that routine tests miss.
2. Genetic factors matter more than lifestyle for certain risks. Lp(a) levels, which affect roughly 20% of people, cannot be changed through diet or exercise — though new medications are in development.
3. Remnant particles are a distinct threat. These unmeasured particles are up to four times more likely to cause heart disease per particle than LDLs.
4. Very high HDL is not necessarily good. The 3-10% of people with very high HDL-cholesterol may actually face higher risks of multiple diseases.
5. ApoB testing offers a better risk assessment. The European Society of Cardiology now endorses apoB counting as a superior measure of heart risk, but it has not yet reached most doctors' offices.

For patients with a family history of early heart disease, or those who have been told their cholesterol is "normal" but remain concerned, asking about apoB or Lp(a) testing could be a valuable conversation to have with their doctor.

Study Limitations: What Scientists Still Don't Know

While the research described in this article represents a major advance in understanding, important questions remain unanswered. The article itself highlights several significant gaps in current knowledge:

• The mechanisms by which very high HDL-cholesterol contributes to disease are not yet fully understood. The alcohol connection explains some cases, but not all, and the "dysfunctional HDL" theory remains a hypothesis rather than a proven fact.
• Researchers have not yet identified which specific proteins on HDL particles mark them as dangerous, and the fact that each particle carries only two or three of 280 possible proteins makes this work extremely challenging.
• The evidence linking very high HDL to conditions like diabetes, cancer, and Alzheimer's is observational, which means it can show associations but cannot prove cause and effect.
• ApoB testing has been endorsed by European cardiology experts, but its adoption into routine practice remains incomplete, and the article notes that most risk calculators used by doctors in Europe and America have not yet incorporated it.
• Treatment options for elevated Lp(a) are still in development, meaning patients with this risk factor currently have no specific therapy available to them.

Recommendations for Patients

Based on the research described in this article, patients can take several practical steps to better understand and manage their cardiovascular health:

1. Know your numbers — all of them. Ask your doctor whether your cholesterol panel includes apoB and Lp(a) measurements, or whether those tests would be appropriate for you, particularly if you have a family history of premature heart disease.
2. Don't be falsely reassured by "normal" LDL. If you have other risk factors — such as high blood pressure, diabetes, or a family history — a normal LDL reading may not tell the whole story.
3. Remember that lifestyle still matters. While Lp(a) levels cannot be changed by diet and exercise, standard LDL cholesterol can be influenced by reducing saturated fats, red meat, and full-fat dairy, and by increasing physical activity and fruit/vegetable intake.
4. Understand that statins are not the only answer for everyone. Statins remain highly effective for lowering LDL, but they do not address elevated Lp(a) or remnant particles.
5. Watch for emerging treatments. Drugs from Amgen, Eli Lilly, and Novartis targeting Lp(a) are on the horizon, and patients with known Lp(a) elevation may want to discuss these developments with their cardiologist.
6. If you have very high HDL, talk to your doctor. Rather than assuming higher is better, discuss what your HDL level might mean, especially considering the associations with heavy drinking and metabolic conditions.

The era of "good" versus "bad" cholesterol is giving way to a much more sophisticated understanding of the entire lipoprotein ecosystem. For patients, the most important takeaway is this: a standard cholesterol test is a useful starting point, but it is no longer the complete story of your heart health.

Frequently Asked Questions

What is lipoprotein(a) and should I ask my doctor about it?

Lipoprotein(a), or Lp(a), is a dangerous particle formed when a protein attaches to LDL. High levels raise heart disease risk. It is not measured in standard cholesterol tests and is not changed by diet or exercise. About 20% of people carry the genetic variant. Ask your doctor if Lp(a) testing is appropriate for you, especially with a family history.

My LDL cholesterol is normal, but I have a family history of early heart disease. What else should I ask?

Ask about apoB testing, which counts dangerous cholesterol particles and is more precise than standard LDL measurement. The European Society of Cardiology endorses it, though it is not yet widely used. Studies show 20-30% of people have low LDL but high apoB, putting them at risk that routine tests miss. Also ask about Lp(a).

Is very high HDL cholesterol always good for my health?

No. Very high HDL, found in 3-10% of people, has been linked to diabetes, fatty-liver disease, chronic kidney disease, age-related macular degeneration, Alzheimer's disease, and cancer. Scientists think HDL stuffed with cholesterol may become dysfunctional. The relationship between HDL and health is U-shaped, so too little and too much can both be harmful.

What are remnant particles and why are they dangerous?

Remnant particles are leftovers of large lipoproteins that carry fat from food. They typically hold several times more cholesterol than an LDL particle and, on a per-particle basis, are up to four times more likely to cause heart disease. They are not measured in standard cholesterol tests, so they can go undetected.

What is the difference between LDL cholesterol and apoB?

LDL cholesterol measures the amount of cholesterol inside LDL particles. ApoB is a protein on each dangerous particle, so counting apoB tells you the number of particles. Because each dangerous particle has one apoB, counting apoB gives a more precise estimate of heart risk than measuring total cholesterol content.

My doctor said my HDL cholesterol is low. How worried should I be?

Low HDL can signal underlying metabolic conditions such as diabetes, which raises remnant particles and heart risk. However, low HDL alone does not prove harm. Talk to your doctor about your full risk picture, including apoB and Lp(a) testing. Lifestyle changes that improve overall health remain important regardless.

Can diet and exercise lower all types of bad cholesterol?

Diet and exercise can lower standard LDL cholesterol: reduce saturated fats, red meat, and full-fat dairy, and increase physical activity and fruit/vegetable intake. However, lipoprotein(a) levels cannot be changed by diet or exercise. Statins lower LDL but do not lower Lp(a) or remnant particles. New targeted treatments are in development.

My standard cholesterol test shows normal LDL, but I have a family history of early heart disease. Should I get a second opinion to check for hidden risks like Lp(a) or apoB?

Yes, a second opinion can be valuable if your standard cholesterol panel shows normal LDL but you have a family history of early heart disease. Standard tests miss lipoprotein(a) and remnant particles, which are dangerous and affect many people. About 20-30% of people have low LDL but high apoB, meaning their particle count raises risk that routine tests miss. ApoB testing counts dangerous particles and is endorsed by European cardiologists, though not yet routine. Ask your doctor about apoB and Lp(a) testing. Diagnostic Detectives Network provides independent expert second opinions.

Source Information

Original article title: There’s more to cholesterol than simply “good” or “bad”

Publication: The Economist, Science & Technology section (print edition headline: "Re-thinking cholesterol")

Publication date: November 25, 2025 (appeared in the November 29, 2025 edition)

Author: The Economist (staff-written feature; illustration by Cristina Spanò)

Key researcher mentioned: Sekar Kathiresan, Harvard Medical School (2012 HDL genetics study)

This patient-friendly article is based on peer-reviewed research and scientific reporting as presented in the original publication. Cholesterol science continues to evolve rapidly, and patients should consult their healthcare providers for personalized advice based on their individual risk factors.