Cholesterol is a substance essential for the normal functioning of the human body. It is a type of lipid (fatty compound) produced in the liver; it is also contained in food. An elevated level of cholesterol in the blood does not cause any immediate symptoms, but it is a strong risk factor for cardiovascular disease, mainly heart attack.

Types of cholesterol

Cholesterol circulates in the blood bound to proteins in lipoprotein complexes. Some of the lipoproteins have a protective effect; others are harmful.

• High-density lipoprotein (HDL): HDL transports cholesterol from the cells in the body towards the liver, where it is broken down or removed as waste material. That is why it is 'good cholesterol and a high level of HDL cholesterol is beneficial for health.
• Low-density lipoprotein (LDL): LDL transports cholesterol from the liver to the cells that need it. If the body can’t use up all LDL cholesterol, the excess builds up in the walls of arteries and creates atherosclerotic plaques. LDL is therefore 'bad cholesterol and a high level is bad for health.

Blood tests are available to assess either level of total cholesterol in the blood (the lower, the better) or for lipid profile which usually includes total cholesterol, HDL cholesterol (high is good), LDL cholesterol (low is good), total cholesterol/HDL ratio (low is good) and triglycerides (low is good).

Consequences of high cholesterol

Cholesterol deposits in the arteries restrict the blood flow to the brain, heart and the rest of the body. The cholesterol plaques also increase the risk of blood clots leading to a sudden occlusion of an artery which in the brain would cause stroke and, in the heart, a heart attack. Consequences of hypercholesterolaemia include:

• Angina and heart attack
• Stroke and TIA (transient ischaemic attack, TIA = ministroke)
• Peripheral vascular disease (PVD, narrowings of the arteries in the legs), also known as peripheral arterial disease (PAD)
  
  

Causes of high cholesterol

Familial hypercholesterolaemia (FH) - a rare genetic condition that leads to very high cholesterol regardless of eating habits.
Genetic disposition - in most people, the problem is not in one single gene (as is the case in FH), but elevated cholesterol is a consequence of the interaction between many different genes.
Unhealthy diet - dietary cholesterol and saturated fats in the food obviously increase cholesterol level.
Smoking - some substances in cigarettes may block the transport of LDL from cells to the liver, increasing its level in the arteries leading to the narrowing of the arteries; smoking also greatly increases overall cardiovascular risk.

Diagnosis

Lipid profile or at least total cholesterol should be checked in patients with:

• Age over 40 years
• Established coronary artery disease (CAD), peripheral vascular disease (PVD) and stroke or mini-stroke (TIA)
• Family history of premature heart disease
• Diabetes, hypertension or underactive thyroid
• Unhealthy weight and obesity
• Familial hypercholesterolaemia
  
  

How to reduce cholesterol?

A healthy and balanced diet with wholegrain cereals, fruit and vegetables is the first step to lower cholesterol. Quit smoking, reduce alcohol consumption to recommended limits (below 14 units a week) and do regular exercise. If the lifestyle changes are not sufficient, your GP or consultant may prescribe statins (e.g. simvastatin, atorvastatin, rosuvastatin) to reduce your level of cholesterol. A scoring system QRISK3 guides the indication for statins. The first-line treatment is normally atorvastatin 20mg once daily for patients with QRISK3 score 10% or more (i.e. with 10% or higher risk of developing cardiovascular disease over the next 10 years).