Cholesterol Explained: LDL, HDL, Triglycerides and What to Do About Them
Cholesterol has a bad reputation, but your body needs it. It is a waxy substance used to build cell membranes, make hormones and produce vitamin D and bile. The trouble starts when too much of the wrong kind circulates in the blood and builds up in artery walls.
Where cholesterol comes from
Most of your cholesterol, roughly 70 to 80 per cent, is made by the liver. The rest comes from food. That explains why two people can eat similar diets yet have very different results: genetics and liver metabolism matter a great deal.
Reading your lipid panel
A standard blood test, usually fasting or non-fasting, reports several numbers.
- LDL cholesterol carries cholesterol from the liver to the tissues. When there is too much, it deposits in artery walls and forms plaque. This is why it is called the bad cholesterol and why it is the main treatment target.
- HDL cholesterol carries cholesterol back to the liver for disposal. Higher levels are generally protective, though raising HDL with drugs has not reliably reduced events.
- Triglycerides are the main fat in the blood. High levels are linked to excess sugar, refined carbohydrate, alcohol, obesity and diabetes, and very high levels can inflame the pancreas.
- Non-HDL cholesterol is total cholesterol minus HDL and captures all the harmful particles. It is increasingly used because it does not require fasting.
- Lipoprotein(a) is a genetically determined particle worth measuring once in a lifetime, especially with a family history of early heart disease.
Typical targets for the general population are LDL below about 3 mmol/L (115 mg/dL), but people with diabetes, existing heart disease or a high risk score are advised to aim much lower, sometimes below 1.4 mmol/L (55 mg/dL). Your doctor will set a target that fits your personal risk.
Why high LDL is dangerous
High LDL itself causes no symptoms. Over decades, plaque narrows the arteries and can rupture, triggering a clot. If that happens in a heart artery, the result is a heart attack; in a brain artery, a stroke; in the legs, painful circulation problems. Lowering LDL by even a modest amount over many years reduces these events substantially, and the longer your LDL is low, the greater the benefit.
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Familial hypercholesterolaemia
A common but under-diagnosed inherited condition, familial hypercholesterolaemia, causes very high LDL from birth. It affects about one in 250 people. Clues include an LDL above 5 mmol/L (190 mg/dL), yellowish deposits around the eyes or tendons, and relatives with heart disease in their forties or fifties. Because the condition runs in families, relatives should be tested, and treatment should start early.
Food that helps
- Soluble fibre from oats, barley, beans, lentils, apples and psyllium binds cholesterol in the gut.
- Unsaturated fats from olive oil, nuts, seeds and fish can replace saturated fat, which raises LDL.
- Plant sterols and stanols, added to some spreads and yoghurts, modestly lower LDL.
- Fewer trans fats and less processed meat, which both worsen the lipid profile.
- Less sugar and alcohol to lower triglycerides.
Eggs and shellfish are less of a concern than once thought for most people, since saturated fat has a larger effect than dietary cholesterol.
Activity, weight and smoking
Regular aerobic exercise raises HDL and lowers triglycerides. Losing even five to ten per cent of body weight improves nearly every number. Stopping smoking improves HDL and, more importantly, removes a major driver of artery damage.
Medication
Statins are the first-line treatment. They reduce cholesterol production in the liver and have been shown in huge trials to cut heart attacks and strokes. Most people tolerate them well. Muscle aches occur in a minority, and a different statin or dose often solves it. Serious side effects are rare.
If a statin is not enough or not tolerated, options include ezetimibe, which blocks absorption in the gut; bempedoic acid; and injectable PCSK9 inhibitors or inclisiran for very high-risk patients. For high triglycerides, lifestyle change comes first, with specific treatments reserved for severe cases.
How often to test
Adults should have a baseline test, then repeat every few years if normal, or more often if treated. After starting medication, a check after six to twelve weeks confirms it is working.
Key points
Cholesterol is a risk factor you can measure and change. Know your numbers, understand your overall risk, and use food, activity and, where appropriate, medication to bring LDL down for the long term.
This article is for general information and is not a substitute for professional medical advice. If you are worried about your health or have symptoms, speak to a doctor or other qualified health professional.