Cholesterol Dr Trisha Macnair Cholesterol is essential for our bodies to work, so why are there so many health warnings about high cholesterol levels? We look at what cholesterol does and why raised cholesterol is damaging to health.

In this article

What is cholesterol? Cholesterol and food

Lipoprotein levels What are healthy levels?

How low do you go? What's the treatment?

Cholesterol forms part of the outer membrane that surrounds every cell. It's used to insulate nerve fibres (and so make nerve signals travel properly) and make hormones, which carry chemical signals around the body.

Without cholesterol, your body wouldn't work - it's vital to ensure the body's normal function.

Too much cholesterol in the blood, however, increases the risk of coronary heart disease and disease of the arteries.

One of the biggest misconceptions people have is that food's packed with cholesterol. In fact, very little cholesterol is found in foods. The main culprits are eggs, offal and shellfish.

What's important is the type of fat in the food you choose, especially saturated fat. Once inside the body, the liver turns this fat into cholesterol.

Knowing your cholesterol level isn't, on its own, enough to tell you your personal risk of heart disease. You also need to know about lipoproteins. These are special molecules that carry or transport cholesterol around the body.

There are three main types:

• Low-density lipoprotein (LDL), often known as bad cholesterol - this carries cholesterol from the liver to the cells and, if supply exceeds demand, can cause harmful build-up of cholesterol
• High-density lipoprotein (HDL), or good cholesterol - this takes cholesterol away from the cells and back to the liver, where it's either broken down or excreted
• Triglycerides

The greatest danger is when someone has high levels of LDL cholesterol and trigylcerides, and low levels of HDL cholesterol.

The average total cholesterol level in the UK is 5.5mmol/l for men and 5.6mmol/l for women, which is above a normal level. So does that mean that most people need to take anticholesterol drugs?

In recent years, we've come to realise that to decide whether an individual's cholesterol levels are dangerous, these levels need to be considered in the light of the person's overall risk of heart disease.

In particular, it's the balance of different types of lipoproteins, rather than the overall total cholesterol level, that matters.

This overall risk is determined by a combination of factors, including age, gender, family history of heart disease, and whether someone smokes, is overweight, has high blood pressure or diabetes.

The higher the risk of heart disease (for example, a male smoker with high blood pressure and diabetes), the greater the need to get cholesterol levels down.

But what constitutes a healthy cholesterol level is controversial, even among doctors.

The National Institute for Health and Clinical Excellence (NICE) and Department of Health cholesterol guidelines, which is the policy doctors follow, are:

• Total cholesterol - less than 5.0mmol/l
• LDL cholesterol - less than 3.0mmol/l

However, the Joint British Societies (a group of the main UK expert societies involved in cardiovascular disease) recommend different cholesterol limits for people who have, or are at risk of, coronary heart disease:

• Total cholesterol - less than 4.0mmol/l
• LDL cholesterol - less than 2.0mmol/l

These guidelines match the more stringent recommendations used in Europe.

NICE is currently reviewing its national policy guidelines.

How hard people who have little risk of heart disease should strive to keep their cholesterol levels down below 5mmol/l is even more controversial.

Some believe the lower the cholesterol level, the better in terms of preventing heart disease. These people argue that because cholesterol-lowering drugs mostly appear to have minimal side-effects, almost everyone should take them.

But other experts argue that the research evidence doesn't show any particular benefit for certain low-risk groups, such as women who don't have a history of heart disease, and some point to recent concerns about side-effects, such as damage to muscles or the kidneys.

With anticholesterol drugs now being sold without prescription at the pharmacy, the decision about how far to control cholesterol is being pushed into the consumer's hands.

One in 500 people has high cholesterol because of an inherited problem, called familial hyperlipidaemia. If this includes you, you can get more information from Heart UK.

The first steps in treating high cholesterol levels are:

• Regular physical activity
• Healthy eating

The latter means cutting down on fats, especially a type called trans fats, and replacing saturated fats with unsaturated alternatives. There are also some foods that may help to lower cholesterol levels, particularly garlic, soya, oats, corn and selenium-enriched cereals.

For advice on healthy eating for hearts, contact the British Heart Foundation.

After taking steps to lower cholesterol, lipid-lowering drugs should be used.

This article was last medically reviewed by Dr Rob Hicks in December 2007