LDL (Low-density lipoprotein)
Understanding Cholesterol and LDL
How your body makes and uses it — and what levels support a longer, healthier life
TL;DR
- Cholesterol is essential for every cell, but imbalances raise long-term health risks.
- LDL (low-density lipoprotein) carries cholesterol from the liver to cells; too much for too long raises the risk of atherosclerosis and heart disease.
- HDL (high-density lipoprotein) removes excess cholesterol from the bloodstream, protecting arteries.
- Both very high and very low LDL levels are linked to higher all-cause mortality.
- Aim for LDL 100–159 mg/dL (2.6–4.1 mmol/L) for optimal longevity and maintain healthy HDL.
- Most cholesterol is made by your body, not absorbed from food — genetics, metabolism, and lifestyle have the greatest influence.
What Cholesterol Is and Why It Matters
Cholesterol is a waxy, fat-like substance vital for health.
Your body uses it to:
- Build and repair cell membranes
- Produce hormones such as oestrogen, testosterone, and cortisol
- Synthesise vitamin D
- Make bile acids that help digest fats
Because cholesterol does not dissolve in water, it travels through your blood inside tiny carriers called lipoproteins — combinations of fat and protein that act like transport vehicles.
| Type | Role | Common Association |
|---|---|---|
| LDL (Low-Density Lipoprotein) | Delivers cholesterol to cells | High levels increase arterial plaque risk |
| HDL (High-Density Lipoprotein) | Removes cholesterol from blood | High levels protect arteries |
| VLDL (Very-Low-Density Lipoprotein) | Carries triglycerides | High levels linked to metabolic disease |
| Triglycerides | Energy storage fat molecules | High levels raise cardiovascular and metabolic risk |
Where Cholesterol Comes From
Around 75–85% of cholesterol is made by your liver and intestines.
Only 15–25% comes from food.
For most people, blood cholesterol levels depend more on genetics, metabolism, and inflammation than on dietary cholesterol itself.
(Harvard Health, 2024)
| Source | Contribution | Notes |
|---|---|---|
| Liver and intestines | 75–85% | 800–900 mg/day synthesised internally |
| Diet | 15–25% | ~300 mg/day absorbed |
| Total | ~1,000 mg/day | Excess removed via bile and stool |
Why LDL and HDL Matter
LDL delivers cholesterol to cells, which is necessary for healthy body function.
However, when LDL levels stay high for years, cholesterol can build up inside artery walls, forming plaques that narrow and stiffen arteries — a process called atherosclerosis.
HDL helps clear excess cholesterol, carrying it back to the liver for recycling or removal.
This is why HDL is often called “good” cholesterol and LDL “bad” — both are needed, but in the right balance.
Healthy Cholesterol Ranges
| Marker | Optimal Range (mg/dL) | mmol/L | Meaning |
|---|---|---|---|
| Total cholesterol | 180–220 | 4.65–5.69 | Associated with lowest all-cause mortality |
| LDL (“bad”) | 100–159 | 2.6–4.1 | Lowest population mortality range |
| HDL (“good”) | ≥50 (men) / ≥60 (women) | ≥1.3 / ≥1.55 | Higher levels protect arteries |
| Triglycerides | 70–150 | 0.8–1.7 | Higher levels raise risk of heart and metabolic disease |
| Non-HDL (Total – HDL) | <130 | <3.36 | Strong marker for cardiovascular prevention |
Extremely low LDL (<70 mg/dL) and very high LDL (>190 mg/dL) both correlate with increased all-cause mortality over time.
The safest range for most adults is moderate, not extreme.
How Cholesterol Is Tested
A lipid profile or cholesterol panel is a simple blood test that measures:
- Total cholesterol
- LDL cholesterol
- HDL cholesterol
- Triglycerides
- Sometimes non-HDL cholesterol or apolipoproteins
It can be done fasting or non-fasting in most labs.
Testing regularly helps track long-term trends rather than focusing on one result.
How Often to Test
- Healthy adults: every 4–6 years
- With risk factors (diabetes, high blood pressure, obesity, family history): once per year
- On medication: 4–12 weeks after starting, then every 6–12 months
- Children with inherited high cholesterol: start testing between ages 9–11 and recheck every 3–5 years
LDL Levels and Longevity
Large global studies show a U-shaped or J-shaped curve between LDL cholesterol and all-cause mortality:
both very low and very high LDL increase long-term risk.
The lowest risk of death across populations typically occurs at LDL 100–159 mg/dL (2.6–4.1 mmol/L).
| LDL-C Range (mg/dL) | mmol/L | Mortality Pattern | Key Sources |
|---|---|---|---|
| <70 | <1.8 | Higher risk in older adults and non-statin users | [1–8] |
| 70–99 | 1.8–2.6 | Slightly increased or neutral | [1–8] |
| 100–129 | 2.6–3.3 | Lowest overall risk | [2–8] |
| 130–159 | 3.4–4.1 | Slight increase with time | [3–9] |
| ≥160 | ≥4.1 | Clearly higher long-term risk | [3–9] |
Other Important Markers
Some advanced tests go beyond the standard lipid panel.
These markers offer deeper insight into how cholesterol particles behave and your real cardiovascular risk.
You may need them if your regular test results are borderline, or if your triglycerides or blood sugar are high.
| Marker | Description | Why It Matters |
|---|---|---|
| Triglycerides | Fat molecules for energy storage | Levels above 150 mg/dL (>1.7 mmol/L) raise cardiovascular disease (CVD) risk |
| ApoB (Apolipoprotein B) | Protein that counts LDL particles | Each LDL particle carries one ApoB; high ApoB means more atherogenic particles and higher CVD risk |
| ApoA-I (Apolipoprotein A-I) | Main protein in HDL | Higher levels are linked to vascular protection |
| Lipoprotein(a) [Lp(a)] | Inherited LDL-like particle | High levels increase lifetime heart disease risk regardless of diet |
| hs-CRP | Inflammation marker | High values suggest increased vascular inflammation |
| Non-HDL cholesterol | Total cholesterol minus HDL | Reflects all “bad” cholesterol types combined |
Testing these is useful when:
- Standard cholesterol results are unclear
- Family history of early heart disease exists
- You have diabetes, kidney disease, or metabolic syndrome
- You’re on therapy but LDL levels don’t explain residual risk
(UT Southwestern, 2024)
Evidence-Based Ways to Lower LDL
| Action | Typical LDL Change | Why It Helps |
|---|---|---|
| Statins (prescribed) | ↓ 20–50% | Block liver cholesterol synthesis |
| Weight loss (5–10%) | ↓ 5–20% | Reduces liver fat and improves metabolism |
| Diet (less saturated fat, more fibre) | ↓ 10–15% | Enhances bile excretion and gut lipid clearance |
| Exercise (150 minutes per week) | ↓ 5–10% | Raises HDL and lowers triglycerides |
| Quit smoking | ↑ HDL by about 10% | Improves blood vessel function |
Why Some People Have High or Low Cholesterol
| Cause | Effect |
|---|---|
| Genetics (familial hypercholesterolaemia) | Lifelong high LDL regardless of lifestyle |
| Diet high in saturated fats | Raises LDL, may lower HDL |
| Lack of exercise | Lowers HDL and worsens triglycerides |
| Obesity and insulin resistance | Raises triglycerides and LDL particle count |
| Smoking | Damages arteries and lowers HDL |
| Thyroid or liver disease | Alters cholesterol production and clearance |
| Chronic illness or malnutrition | Can lower cholesterol too much |
Even people with excellent diets can have high cholesterol due to genetics — and some with poor diets maintain average levels due to fast metabolism.
Key Insights
- Most cholesterol is made by the body — not absorbed from food.
- Focus on fat quality rather than cholesterol content.
- Healthy habits can significantly lower LDL within 3–6 months.
- Track cholesterol trends over time instead of single readings.
- Both very low and very high cholesterol levels are linked to shorter lifespan.
Key Takeaway
LDL is essential but potentially harmful when chronically high or abnormally low.
Moderate levels between 100–159 mg/dL (2.6–4.1 mmol/L) are linked to the longest average lifespan across multiple populations.
Focus on sustainable habits and regular monitoring rather than chasing extreme numbers.
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Disclaimer: This article is for informational purposes only and not a substitute for medical advice.
Scientific summaries were compiled and synthesised using the AI models and peer-reviewed research.