This cholesterol factsheet is for people who want to learn more about cholesterol levels and health. Cholesterol is a fat-like material in your blood. Your body makes its own cholesterol. When you eat foods that have lots of fat or cholesterol, you can have too much cholesterol in your blood. It is essential for good health and is found in every cell in the body. However, a high cholesterol level in the blood (hypercholesterolaemia) is associated with an increased risk of heart disease and stroke. Seven out of 10 people over 45 have high cholesterol.

• 107 million, or 1 in 5 adults, has cholesterol levels above 200 mg/dL.
• Almost 38 million more have levels above 240 mg/dL.
• More women over age 45 have high cholesterol than men.
• Almost 30 million prescriptions are written each year for cholesterol lowering drugs, accounting for $20 billion in annual sales for the pharmaceutical industry.
• Americans spend $10 billion per year on the statin drug, Lipitor alone
• In 2001, the statin drug, Baycol used to lower cholesterol was taken off the market due to toxic side effects.
• Most drugs prescribed today to lower cholesterol are statin drugs.
• Asians on average have an LDL cholesterol level of less than 95 because of their low fat diet.  Anything under 100 for LDL cholesterol is considered good.
• Diet and lifestyle changes, without the use of drugs, have been shown to decrease LDL cholesterol in one year’s time by 40 percent on average (from 144 down to 87 mg/dL.)

Why is high cholesterol a problem?

Cholesterol can build up on the inside the blood vessels of your heart. If too much cholesterol builds up, then the blood cannot flow through to your heart. This can cause a heart attack. The main risk associated with high cholesterol is cardiovascular disease (CVD). This includes diseases of the heart and blood vessels. High cholesterol causes blood vessels to become narrowed with fatty deposits called plaques. This can result in heart attacks, strokes and blood vessel problems. For more information see the separate HealthyLifeReviews health factsheets Angina, Heart attack and Stroke.

Types of cholesterol

Cholesterol is transported around the body in the blood attached to a protein. This combination of fat and protein is called a lipoprotein. Lipoproteins can be high density (HDL), low density (LDL) or very low density (VLDL), depending on how much protein there is in relation to fat.

LDL (low density lipoprotein)

Most of the body's cholesterol is transported as LDL. This is made up of mostly fat and a small amount of protein. Too much LDL in the blood can cause cholesterol deposits to build up in the arteries, making it harder for the blood to flow through these blood vessels. High levels of LDL in the blood are associated with an increased risk of CVD. So LDL is sometimes referred to as " bad cholesterol".

HDL (high density lipoprotein)

A small amount of cholesterol is transported as HDL, which is mostly made up of protein and a small amount of fat.

HDL actually helps prevent cholesterol deposits building up in the arteries. Having low levels of HDL (compared with LDL) in the blood is associated with an increased risk of CVD. So HDL is sometimes referred to as "good cholesterol". Women tend to have a higher levels of HDL cholesterol than men.

If the total cholesterol (TC) level is too high, this is one risk factor for health problems. However, it's important to consider the relative amounts of HDL and LDL. This is often referred to as the TC:HDL ratio. A high level of HDL and a low level of LDL (so a low TC:HDL ratio) is desirable.

Triglycerides

Triglycerides are a different type of fat, which mostly come from fats in your food. Energy that is eaten and not used immediately is converted into triglycerides and transported to fat cells for storage. This is an important source of stored energy.

Although most triglycerides are stored in fat tissue, low levels are also found in the blood. They are carried in the blood as very low density lipoproteins (VLDL).

A raised level of blood triglycerides together with high LDL can increase the risk of heart disease, particularly in people with diabetes.

What causes high cholesterol?

There are several factors that may contribute to high blood cholesterol:

• a diet that's high in saturated fat and, less so, high in cholesterol (see How diet affects cholesterol below)
• lack of exercise may increase LDL ("bad") cholesterol and decrease HDL ("good") cholesterol
• family history - people are at a higher risk of high cholesterol if they have a direct male relative aged under 55 or a female relative aged under 65 affected by heart disease
• being overweight, which may increase LDL ("bad") cholesterol and decrease HDL ("good") cholesterol
• age and sex - cholesterol generally rises slightly with increasing age, and men are more likely to be affected than women
• drinking more than the recommended amount of alcohol (ie more than three to four units per day for men and two to three units per day for women)

Rarely, high cholesterol can be caused by a condition that runs in the family called a lipid disorder (familial hypercholesterolaemia). About one in 500 people have this condition.

Other health conditions such as poorly controlled diabetes, certain kidney and liver diseases and an underactive thyroid gland may also cause cholesterol levels to rise. Some medicines such as beta-blockers, steroids or thiazides (a type of diuretic) may also affect blood lipid levels.

How diet affects blood cholesterol

Only a small amount of cholesterol comes directly from your diet - the majority is produced by your liver. However, if your diet is high in saturated fats and cholesterol this can cause your liver to produce more LDL ("bad") cholesterol. The amount that diet influences cholesterol levels varies from person to person.

Measuring cholesterol

The amount of cholesterol in your blood is measured in units called millimoles per litre of blood, usually shortened to "mmol/litre" or "mmol/l". America uses the units milligrams per decilitre of blood: "mg/dl" instead. Current UK guidelines state that it is desirable to have a total cholesterol level under 5mmol/l, and an LDL level under 3mmol/l.

In order to estimate your risk of getting CVD, the best indicator of risk is your TC:HDL ratio. A lower ratio is desirable, because this indicates that you have high levels of HDL.

Measuring cholesterol involves a simple 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 test. A blood sample may be taken either by using a needle and a syringe, or by using a finger prick. You can have this test at your GP surgery, at a hospital appointment, or as part of a health assessment examination.

Home-testing kits for cholesterol may not be very accurate. Also, cholesterol is just one of the risk factors for heart disease. It should ideally be measured under medical supervision so that other important issues, such as blood pressure, age and whether or not you smoke, are taken into account. Speak to your pharmacist about your result if you do choose a home testing kit.

Who should have a cholesterol test?

Anyone who has any cardiovascular disease, such as coronary heart disease, peripheral vascular disease (disease in the blood vessels that supply the limbs) or stroke, should have their cholesterol measured by a doctor.

Anyone, even children, with a family history of familial hypercholesterolaemia should have their cholesterol measured.

Anyone aged 35 or over should consider having their cholesterol measured if they have one or more of the following risk factors for CVD: family history of early heart disease, diabetes, high blood pressure, or if they smoke.

Diagnosis

Having a high cholesterol level does not cause symptoms. Most people find out they have high cholesterol when they have their blood cholesterol measured as part of a medical check-up. Alternatively, it may be identified after other health problems, such as heart disease, have been diagnosed.

Treatment

The main aim of lowering cholesterol is to reduce the risk of heart disease. The type of treatment depends on the overall risk of heart disease.

There are two ways to help lower high cholesterol. The first is with simple lifestyle changes including changing diet, managing weight and increasing exercise. The second is to combine lifestyle changes with cholesterol-lowering medicines.

Diet

Healthy eating can reduce cholesterol. Your diet should be low in saturated fats in particular, and low in fat overall. Biscuits, cakes, pastries, red meat, hard cheese, butter and foods containing coconut or palm oil all tend to be high in saturated fats, so cut down on these foods.

Large amounts of cholesterol are found in a few foods, including eggs, offal such as liver and kidneys, and prawns. However, if you're already eating a balanced diet, you don't need to cut down on these foods unless your GP or dietitian have advised you to.

It's also important to eat plenty of fibre, especially soluble fibre, which is thought to lower cholesterol. It's found in fruits and vegetables, beans and oats. Aim to eat at least five portions of fruit and vegetables each day. For more information see the HealthyLifeReviews factsheet, Healthy eating.

There is some evidence that foods containing substances called plant sterols or plant stanols, such as the brands Benecol or Flora pro.activ, in combination with a low fat diet and physical activity, can help to lower cholesterol.

Medicines

Cholesterol-lowering medicines are considered for people who already have CVD, or are at high risk of getting it because they have other risk factors.

The main group of medicines for lowering cholesterol are statins. Examples include simvastatin (Zocor) and atorvastatin (Lipitor). They work by reducing the production of cholesterol in the liver. Occasionally these drugs have side-effects such as indigestion and muscle pains. Other types of drugs to reduce cholesterol are called fibrates, nicotinic acids and cholesterol absorption inhibitors such as ezetimibe (Ezetrol) but these are generally less effective or have more side-effects. Your doctor will tell you more about these medicines.