Cholesterol is a fatty substance known as a lipid and is vital for the normal functioning of the body. It’s mainly made by the liver, but can also be found in some foods.
Having an excessively high level of lipids in your blood (hyperlipidemia) can have an effect on your health.
High cholesterol itself doesn’t usually cause any symptoms, but it increases your risk of serious health conditions.
Cholesterol is carried in your blood by proteins. When the two combine, they’re called lipoproteins.
The two main types of lipoprotein are:
- high-density lipoprotein (HDL) – carries cholesterol away from the cells and back to the liver, where it’s either broken down or passed out of the body as a waste product; for this reason, HDL is referred to as “good cholesterol”, and higher levels are better
- low-density lipoprotein (LDL) – carries cholesterol to the cells that need it, but if there’s too much cholesterol for the cells to use, it can build up in the artery walls, leading to disease of the arteries; for this reason, LDL is known as “bad cholesterol”
The amount of cholesterol in the blood – both HDL and LDL – can be measured with a blood test.
The recommended cholesterol levels in the blood vary between those with a higher or lower risk of developing arterial disease.
Why should I lower my cholesterol?
Evidence strongly indicates that high cholesterol can increase the risk of:
- narrowing of the arteries (atherosclerosis)
- heart attack
- transient ischaemic attack (TIA) – often known as a “mini stroke”
- peripheral arterial disease (PAD)
This is because cholesterol can build up in the artery wall, restricting the blood flow to your heart, brain and the rest of your body. It also increases the risk of a blood clot developing somewhere in your body.
What causes high cholesterol?
Many factors can increase your chances of having heart problems or a stroke if you have high cholesterol.
- an unhealthy diet – in particular, eating high levels of saturated fat
- smoking – a chemical found in cigarettes called acrolein stops HDL transporting cholesterol from fatty deposits to the liver, leading to narrowing of the arteries (atherosclerosis)
- having diabetes or high blood pressure (hypertension)
- having a family history of stroke or heart disease
There’s also an inherited condition called familial hypercholesterolaemia, which can cause high cholesterol even in someone who eats healthily.
Read more about the causes of high cholesterol.