Cholesterol is a type of fat this is essential for the functioning of the body. Cholesterol helps produce hormones, protects nerve endings, and helps make up the walls of individual cell.
The amount of cholesterol present in the blood can range from 3.6 to 7.8 mmol/litre. More than 6mmol/litre is considered high, and is a risk factor for arterial disease. Government advice recommends a target cholesterol level of less than 5, but it is estimated that 2 out of 3 adults have a total cholesterol level above this.
Evidence strongly indicates that high cholesterol levels can cause narrowing of the arteries (atherosclerosis), heart attacks and strokes. The risk of coronary heart disease can also increase if cholesterol levels rise. If other risk factors, such as high blood pressure and smoking, are present then the risk increases even more.
Cholesterol is carried in the blood by molecules called lipoproteins. There are several different lipoproteins, but the three main types are:
Low density lipoprotein (LDL) is mostly made up of fat, plus a small amount of protein. It is this sort of cholesterol that can block your arteries, so it is often referred to as 'bad cholesterol'. Low density lipoprotein carries cholesterol from the liver to the cells and can cause a harmful build-up if there is too much for the cells to use. Normally, the blood contains about 70% of LDL, but the level will vary from person to person.
High density lipoprotein (HDL) is mostly made up of protein, plus a small amount of fat. It is this type of cholesterol that can help to reduce a blockage in your arteries, so it is often referred to as 'good cholesterol'. This good cholesterol is thought to prevent arterial disease, as it takes cholesterol away from the cells and back to the liver, where it is either broken down or is passed from the body as a waste product.
Triglycerides are another type of fatty substance present in the blood, which are produced by the liver. Triglycerides are found in dairy products, meat and cooking oils and people who are overweight, eat a diet high in fatty or sugary foods or drink a large amount of alcohol have an increased risk of a high triglyceride level.
Most of the cholesterol that our body needs is manufactured by our liver. However, if we eat foods that are high in saturated fat, it is broken down into LDL, or 'bad cholesterol'. Foods that are high in saturated fat and are therefore broken down into bad cholesterol include butter, cream, cakes, biscuits, bacon, sausages and processed meats.
A high cholesterol level may only be revealed if you have symptoms of narrowing of the arteries (atherosclerosis). These can include:
- Angina - caused by narrowed coronary arteries in the heart
- leg pain on exercising – this could be due to narrowing of the arteries that supply the legs
- blood clots and ruptured blood vessels – these can result in a stroke or mini-stroke (transient ischaemic attack (TIA))
- ruptured plaques – these can lead to a blood clot forming in one of the arteries delivering blood to the heart (coronary thrombosis), and may lead to heart failure if a significant amount of heart muscle is damaged
- thick yellow patches (xanthomas) around the eyes or elsewhere on the skin. These are cholesterol deposits and can often be seen in people with inherited cholesterol or familial cholesterol
Familial cholesterol (inherited cholesterol)
Familial hypercholesterol is a specific genetic defect which causes high cholesterol levels in the blood. People with inherited or familial hypercholesterolaemia (FH) have a lack of low-density lipoprotein receptors that remove cholesterol from the blood.
Familial Hypercholesterolemia (FH) is an inherited disorder that causes very high cholesterol levels and can therefore increases the chance of having a heart attack early in life. If a person has FH, then it is estimated that any children will have a 50% chance of inheriting Familial Hypercholesterolemia.
Cholesterol lowering medication
Statins (HMG-CoA reductase inhibitors) - Statins are a type of medication that are used to lower your blood cholesterol level. The statins do this by blocking the effects of an enzyme (chemical) in your liver that is used to make cholesterol. By lowering your blood cholesterol level through the use of statins, this will help prevent further damage to your carotid arteries and should reduce the risk of a heart attack or stroke occurring.Statins sometimes have mild side effects which can include constipation, diarrhoea, headaches, and abdominal pain. Common statins used are simvastatin and atorvastatin.
Aspirin may be recommended, depending on your age and a number of other factors. A low daily dose of aspirin can prevent blood clots from forming.
Niacin is a B vitamin which, in high doses, can lower LDL cholesterol and raises HDL cholesterol.
Other medications, such as cholesterol absorption inhibitors (ezetimibe), and bile-acid sequestrants, are also sometimes used to treat high cholesterol. However, they may be less effective than other forms of treatment and have more side effects.