HDL 與 LDL 膽固醇

HDL and LDL Cholesterol

HDL and LDL Cholesterol: Should You Be Concerned About LDL, Vascular Inflammation and Eggs?

High LDL cholesterol can increase the risk of atherosclerosis, heart disease and stroke, so it should be checked and managed according to individual risk.
Higher HDL cholesterol is generally associated with lower cardiovascular risk, but raising HDL alone does not replace lowering LDL, controlling blood pressure, stopping smoking and improving the overall diet.
For most healthy adults, one egg a day can usually fit into a balanced diet, while people with high LDL, diabetes, cardiovascular disease or other risk factors should discuss egg intake with a doctor or registered dietitian.

What Are HDL and LDL Cholesterol?

Cholesterol is a lipid that the body needs for cell membranes, hormones and other functions. It travels through the bloodstream inside particles called lipoproteins.

LDL Cholesterol

LDL stands for low-density lipoprotein cholesterol. It is often called “bad cholesterol.”

When LDL remains high, cholesterol can remain in the artery wall and contribute to atherosclerotic plaque. This process may narrow the arteries and raise the risk of:

  • Coronary heart disease

  • Heart attack

  • Ischaemic stroke

  • Peripheral artery disease

The American Heart Association identifies LDL reduction as an important part of cardiovascular disease prevention. The ACC and AHA cholesterol guideline also stresses that treatment decisions should consider more than one laboratory value.

Relevant factors include:

  • Age

  • Blood pressure

  • Smoking

  • Diabetes

  • Family history

  • Previous cardiovascular disease

  • Kidney disease and other risk factors

HDL Cholesterol

HDL stands for high-density lipoprotein cholesterol. It is often called “good cholesterol” because it helps transport some cholesterol back to the liver for processing.

Higher HDL is generally linked with lower cardiovascular risk. However, this does not mean that HDL is always better when it is higher, or that high HDL can cancel out high LDL.

In clinical practice, doctors usually consider:

  1. The LDL level

  2. Whether cardiovascular disease is already present

  3. Diabetes, high blood pressure and kidney disease

  4. The person’s overall cardiovascular risk

Why Should LDL Cholesterol Be Taken Seriously?

Researchers and doctors generally agree that LDL deserves attention, but its meaning depends on the person’s overall risk.

LDL Risk Is Not the Same for Everyone

The same LDL result may have different implications for different people. Extra care is appropriate for people who:

  • Have had a heart attack or stroke

  • Have diabetes

  • Have familial hypercholesterolaemia

  • Smoke or have high blood pressure

  • Have a family history of premature heart disease

  • Have kidney disease or other major risk factors

The American Heart Association notes that lower LDL is generally associated with lower risk for many people, but a doctor should decide whether lifestyle changes, medication or both are appropriate.

High LDL Often Has No Symptoms

High cholesterol usually does not cause noticeable symptoms. Many people discover it only through a blood test or after developing a cardiovascular problem.

You may wish to discuss a lipid test with a doctor if you:

  • Want to assess your cardiovascular risk

  • Have a family history of high cholesterol

  • Have diabetes, high blood pressure or kidney disease

  • Have had heart disease, stroke or peripheral artery disease

  • Take cholesterol-lowering medication

The Debate: Is Cholesterol Mainly a Problem When Blood Vessels Are Inflamed?

Some researchers argue that cholesterol is not the only factor involved in atherosclerosis. Damage to the vascular lining and chronic inflammation may affect how LDL enters the artery wall and how plaques develop.

When the blood vessel wall is affected by factors such as the following, LDL particles may be more likely to enter and remain in the vessel wall:

  • Smoking

  • High blood pressure

  • High blood sugar

  • Oxidative stress

  • Obesity

  • Long-term metabolic dysfunction

After entering the artery wall, LDL may become modified or oxidised. This can trigger local immune activity and contribute to plaque formation.

This view helps explain why some people with only mildly elevated LDL still develop cardiovascular disease. It also shows why cardiovascular risk cannot be judged by a single cholesterol number alone.

The Two Main Views in This Debate

View One: LDL Is an Important Driver of Atherosclerosis

LDL can remain in the artery wall, particularly when the endothelial lining has been damaged. Long-term exposure to high LDL increases the chance of plaque formation and cardiovascular disease.

View Two: The Condition of the Blood Vessels Affects the Impact of LDL

Smoking, high blood pressure, poor blood sugar control, abdominal obesity and chronic inflammation may make blood vessels more vulnerable to the effects of LDL.

Cardiovascular disease is therefore usually the result of several interacting risk factors, not one food or one cholesterol value alone.

Is “Inflammation Is the Real Problem” Accurate?

Only partly.

A more precise explanation is:

Long-term exposure to high LDL increases the risk of atherosclerosis, while vascular injury and chronic inflammation may make this process more likely or accelerate it.

Vascular inflammation should not be treated as a replacement explanation for LDL risk. Even without a clearly elevated inflammation marker, long-term high LDL may still contribute to atherosclerosis.

Likewise, lowering LDL while ignoring smoking, high blood pressure, diabetes, obesity and physical inactivity may not fully reduce cardiovascular risk.

What Does This Mean in Practice?

The most useful approach is not to choose between “cholesterol” and “inflammation.” Both areas deserve attention:

  • Monitor and manage LDL

  • Stop smoking

  • Control blood pressure and blood sugar

  • Maintain a healthy body weight

  • Reduce saturated fat and highly processed foods

  • Eat more vegetables, whole grains, beans, fish and nuts

  • Stay physically active

  • Follow medical advice for diabetes, kidney disease and other chronic conditions

Can Eating More Eggs Harm Your Health?

Eggs contain dietary cholesterol, most of it in the yolk. One large egg contains about 186 milligrams of cholesterol, but dietary cholesterol often has a smaller effect on blood cholesterol than saturated fat.

Why Were Eggs Once Considered Harmful?

Earlier dietary advice focused heavily on dietary cholesterol and often restricted eggs and egg yolks. Later research showed that eggs are frequently eaten with foods such as:

  • Bacon

  • Sausage

  • Ham

  • Butter

  • Full-fat cheese

  • Fried foods

  • Refined carbohydrates and sugary drinks

These foods may add saturated fat, trans fat, salt and excess calories.

When researchers study eggs, they therefore need to distinguish the possible effect of the egg from the effect of the rest of the meal.

What Do Medical Organisations Say Now?

The American Heart Association’s scientific advisory on dietary cholesterol and cardiovascular risk states that:

  • Healthy people can include up to one whole egg per day within a heart-healthy eating pattern

  • Older adults with healthy cholesterol levels may be able to eat up to two eggs per day, depending on their overall diet

  • Dietary advice should focus on the overall pattern rather than one food or nutrient

Mayo Clinic also reports that most healthy people can eat up to seven eggs per week without increasing heart disease risk. The evidence for people with diabetes is less consistent, so personalised advice may be appropriate.

Eggs and Vascular Inflammation

It is not accurate to say that eggs always cause vascular inflammation. It is also too strong to say that eggs have no effect on everyone.

Research findings may vary according to:

  • The overall eating pattern

  • The number of eggs eaten

  • The cooking method

  • Saturated fat intake

  • Diabetes status

  • Existing LDL levels

  • Body weight and metabolic health

  • Other cardiovascular risk factors

For most healthy adults, moderate egg consumption can fit into a diet that also includes vegetables, whole grains and unsaturated fats.

If eggs are regularly eaten with bacon, sausage, butter, fried foods and highly salted processed foods, the saturated fat and total calorie content of the complete meal may deserve more attention than the egg alone.

What Should You Watch When Eating Eggs?

1. Cooking Method

More suitable choices include:

  • Boiled eggs

  • Poached eggs

  • Steamed egg dishes

  • Scrambled eggs made with little oil

  • Eggs served with vegetables

Try to limit:

  • Eggs fried in large amounts of butter

  • Eggs served with bacon, sausage or ham

  • Large amounts of full-fat cheese

  • Egg meals served with fried potatoes and sugary drinks

The concern may be less about the egg itself and more about the saturated fat, salt and calories in the complete meal.

2. Overall Eating Pattern

A heart-conscious eating pattern commonly includes:

  • Vegetables and fruit

  • Whole grains

  • Beans and lentils

  • Fish

  • Nuts and seeds

  • Olive oil or other unsaturated plant oils

  • Low-fat or fat-free dairy

  • Moderate amounts of eggs, fish and lean meat

The American Heart Association highlights Mediterranean-style and DASH-style eating patterns because they focus on overall diet quality rather than one isolated nutrient.

3. Individual Response

People respond differently to dietary cholesterol. Some people see little change in LDL after eating eggs, while others may have a more noticeable response.

If you eat several eggs daily or already have high LDL, consider:

  1. Having a lipid test

  2. Recording your food intake and egg consumption for several weeks

  3. Reducing butter, fatty meat, processed meat and high-fat dairy

  4. Rechecking cholesterol when advised

  5. Never stopping prescribed medication without speaking to your doctor

Who Should Be More Cautious?

General advice for healthy adults may not apply directly to people who:

  • Have coronary heart disease, a heart attack or stroke

  • Have persistently high LDL

  • Have diabetes

  • Have familial hypercholesterolaemia

  • Have chronic kidney disease

  • Take cholesterol-lowering medication

  • Have been told that they have high cardiovascular risk

This does not always mean that eggs must be avoided. It means that egg intake should be considered alongside the person’s complete diet, blood results and treatment goals.

Practical Ways to Lower LDL

Dietary Changes

  • Replace some processed meat with fish, beans and lean protein

  • Reduce fatty beef, fatty pork, poultry skin and full-fat dairy

  • Replace butter with unsaturated plant oils

  • Eat more oats, barley, beans and vegetables

  • Limit fried foods and products containing trans fat

  • Pay attention to portion size and total calorie intake

Lifestyle Changes

  • Stay physically active

  • Maintain a healthy body weight

  • Stop smoking

  • Manage blood pressure and blood sugar

  • Take cholesterol medication exactly as prescribed

Frequently Asked Questions

Is lower LDL always better?

For many people at higher cardiovascular risk, lower LDL is generally associated with greater protection. The appropriate target depends on medical history, current risk and treatment. It is not advisable to copy another person’s target.

Does high HDL mean I do not need to worry about LDL?

No. Higher HDL does not completely offset high LDL, smoking, diabetes or high blood pressure. LDL and overall cardiovascular risk still need to be assessed.

Is one egg a day safe?

For most healthy adults, one egg a day can usually fit into a balanced eating pattern. People with high LDL, diabetes, cardiovascular disease or other risk factors should discuss their intake with a doctor or registered dietitian.

Are egg whites safer?

Egg whites contain no cholesterol and still provide protein. They can be useful when someone needs to limit egg yolks, but the rest of the diet remains important.

Should I have an inflammation test?

General cardiovascular risk assessment does not rely on an inflammation marker alone. A doctor will usually consider lipids, blood pressure, blood sugar, smoking, family history and other clinical information before deciding whether further testing is needed.

If my blood vessels are not inflamed, is LDL harmless?

No. The absence of a clearly elevated inflammation marker does not mean that long-term high LDL is harmless. LDL, endothelial injury and inflammatory responses may influence one another and should be considered together.

References

  1. American Heart Association: Dietary Cholesterol and Cardiovascular Risk

  2. American Heart Association: Making Sense of Cholesterol: The Good, the Bad and the Dietary

  3. American Heart Association: Here’s the Latest on Dietary Cholesterol and How It Fits in With a Healthy Diet

  4. Mayo Clinic: Eggs: Are They Good or Bad for My Cholesterol?

  5. American College of Cardiology: 2018 AHA/ACC/Multi-Society Guideline on the Management of Blood Cholesterol

  6. American Heart Association: 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease

  7. National Heart, Lung, and Blood Institute: Familial Hypercholesterolemia

  8. National Heart, Lung, and Blood Institute: What Is Atherosclerosis?

  9. Libby P: Inflammation in Atherosclerosis

  10. Ross R: Atherosclerosis: An Inflammatory Disease

This article is for health education and does not replace personalised medical advice based on your blood tests, medical history, medication and cardiovascular risk.


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