Cholesterol is a type of fat (lipid) made by your body. It's essential for good health and is found in every cell in your body. However, having a high level of certain types of cholesterol in your blood (hypercholesterolaemia) can increase your risk of cardiovascular disease, such as heart disease and stroke.
If you have high cholesterol, it may affect your heart and blood vessels and increase your risk of developing cardiovascular disease. High cholesterol causes fatty deposits (known as plaques) to build up inside your blood vessels.
In time, the blood vessels supplying your heart may become so narrow they can't deliver enough oxygen to your heart muscle, particularly when you're exerting yourself. This can cause you to feel chest pain (angina). If a fatty plaque breaks off, it may cause a blood clot that can block blood flow to your heart (heart attack), or if the same process occurs in your brain it may cause a stroke.
Cholesterol is transported around your body attached to a protein in your blood. This combination of fat and protein is called a lipoprotein. There are different types of lipoprotein, depending on how much fat there is in relation to protein.
A small amount of your body’s cholesterol is transported as high-density lipoprotein (HDL), which is mostly protein and not much fat. HDL transports excess cholesterol from your tissues (including the walls of arteries) to your liver for disposal. As HDL helps prevent cholesterol building up in your blood vessels, you have a reduced risk of heart disease if you have high levels of this type. This is why HDL is often referred to as ‘good’ cholesterol.
Most of your body's cholesterol is transported as low-density lipoprotein (LDL). It consists mainly of fat, with not much protein. LDL transports cholesterol from your liver to your cells. High levels of LDL increase your risk of cardiovascular disease because LDL causes cholesterol to build up in your blood vessels. LDL is often called ‘bad’ cholesterol.
Triglycerides are another type of lipid that mostly come from fats in your food. Energy from your food that isn’t used immediately is converted into triglycerides and transported to fat cells for storage. This provides you with an important source of stored energy. Although most triglycerides are stored as fat, low levels are also found in your blood. Having a raised level of blood triglycerides together with high LDL can increase your risk of heart disease, particularly if you have diabetes, high blood pressure or you smoke.
If you have a high total cholesterol level, this is a risk factor for future health problems, such as cardiovascular disease. But the ratio of how much HDL you have compared to total cholesterol is important too. This is called your total cholesterol (TC) to HDL cholesterol ratio (TC:HDL). You should aim for a high level of HDL cholesterol and a low level of LDL (a low TC to HDL ratio).
You may only find out that you have high cholesterol if you have a cholesterol test as part of a health check up, or if you develop symptoms of heart disease. Sometimes, yellow patches (called xanthomas) may develop around your eyes or elsewhere on your skin – these are cholesterol deposits and may show that you have high cholesterol.
If you have high cholesterol, it increases your risk of heart disease and stroke. It may also affect arteries elsewhere in your body such as your legs – this is known as peripheral arterial disease.
There are several factors that may contribute to you having high cholesterol. These include:
If you're a man younger than 55 you're more likely to have high cholesterol than a woman. If you’re a woman over 55 and past the menopause, your cholesterol levels are likely to increase.
High cholesterol can sometimes be caused by a condition that runs in your family called familial hypercholesterolaemia (FH). In the UK, about one in 500 people have this condition. It’s not caused by an unhealthy lifestyle but is passed through families by a faulty gene.
Other conditions, such as poorly controlled diabetes, certain kidney and liver diseases and underactive thyroid (hypothyroidism) may also cause your levels of cholesterol or triglycerides to be high. Some medicines such as the oral contraceptive pill, beta-blockers, steroids or thiazides (a type of diuretic) may also affect your blood lipid levels.
Your cholesterol level is measured with a blood test. Usually you will be asked not to eat for 12 hours before the test so that your food is completely digested and doesn't affect the result. Your doctor or nurse may take a blood sample using either a needle and syringe, or a finger prick. You can have your cholesterol tested at your doctor’s surgery, at hospital, or as part of a health assessment examination.
Home-testing kits for cholesterol are also available but may not be very accurate. Speak to your pharmacist about your result if you use a kit.
The amount of cholesterol in your blood is measured in units called millimoles per litre of blood, usually shortened to 'mmol/litre', 'mmol/L' or 'mM'. When looking at your cholesterol levels, your doctor will consider how much HDL you have compared to total cholesterol. This is called your total cholesterol to HDL cholesterol ratio. You can work this out by dividing your total cholesterol level by your HDL level. It’s healthiest to have high HDL, low LDL and low total cholesterol, with total cholesterol to HDL ratio of less than four.
There is no recommended target level of cholesterol, unless you already have cardiovascular disease or are at high risk. In these instances, your cholesterol levels should ideally be:
The levels of cholesterol in your blood can vary from day to day, so your doctor may take a series of different readings before recommending any treatment.
If you’re at high risk of cardiovascular disease or you have a family history of high cholesterol, you should have your cholesterol levels checked. Speak to your doctor about how often it should be tested. Your doctor should check your cholesterol levels every year if you have cardiovascular disease.
If you have high cholesterol, there are two ways in which you can reduce it. The first is with lifestyle changes, which include changing your diet, managing your weight and exercising. The second is to combine lifestyle changes with cholesterol-lowering medicines.
By eating healthily, you can reduce your cholesterol levels. Your diet should be low in saturated fats in particular, and low in fat overall. Biscuits, cakes, pastries, red meat, hard cheese and butter all tend to be high in saturated fats, so it’s good to cut down on these foods.
Some foods such as eggs, prawns and offal (for example, liver and kidneys) contain cholesterol. This type of cholesterol is known as dietary cholesterol and it has a much lower effect on blood cholesterol than saturated fat in your diet. You may need to cut down on these foods if your doctor advises you to.
It's also important to include plenty of fibre in your diet, especially soluble fibre, which helps to lower cholesterol. There is soluble fibre in fruits and vegetables, beans and oats. Aim to eat at least five portions of fruit and vegetables each day. Eating foods containing substances called plant sterols or stanols, contained in some yoghurts or spreads, may help to lower high cholesterol, but they are not a substitute for a healthy diet.
If you're overweight, losing your excess weight can reduce your LDL levels and increase your HDL levels. Increasing your physical activity may enhance the cholesterol-lowering effects of your diet.
As high cholesterol can increase your risk of heart disease, you should reduce any additional risk of developing it, such as by stopping smoking.
Medicines are generally recommended either if you already have cardiovascular disease or if your risk of getting it is more than 20 percent over 10 years. Your risk can be calculated by your doctor, using a computerised calculation that takes into account a number of other risk factors. The aim of treatment for people with cardiovascular disease is to reduce total cholesterol levels by a quarter or to less than 4mmol/L.
The main group of medicines for lowering cholesterol are called statins. Statins available in the UK include simvastatin, atorvastatin, fluvastatin, pravastatin, and rosuvastatin. These medicines work by reducing the production of cholesterol in your liver, but can have side-effects such as indigestion and muscle pains.
Other types of medicines used to reduce cholesterol include fibrates, nicotinic acid and cholesterol-absorption inhibitors such as ezetimibe (Ezetrol), but these are generally less effective than statins or have more side-effects. If you have very high cholesterol, your GP may prescribe ezetimibe with statins. Your doctor can tell you more about these medicines and suggest the most suitable treatment for you.
You may be able to prevent high cholesterol by keeping to a healthy weight and eating a diet that is low in saturated fat. Try to include at least two portions of fish per week in your diet, of which at least one should be an oily fish such as mackerel or salmon. Try to take regular exercise, avoid smoking and stick to recommended limits of alcohol.
If you don’t have high cholesterol, consuming products containing plant sterols or stanols, such as yogurts or spreads, is not recommended (and they are not suitable for women who are pregnant or breastfeeding).
Produced by Krysta Munford, Bupa Health Information Team, January 2013.
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This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.
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