What is cholesterol?
Cholesterol is a soft waxy substance found in many different parts of the body, including the nervous system, skin, muscles, liver, intestines and heart.
It is needed for a number of bodily processes including the production of hormones, bile acid and vitamin D. It is carried around the body within the bloodstream.
Most cholesterol in our bodies is made in the liver, but it's also found in foods of animal origin, such as eggs, offal and shellfish.
Why is cholesterol important?
According to the British Heart Foundation, almost half of all heart disease deaths in the UK are due to raised blood cholesterol levels; 59% of men and 60% of women have raised levels.
Is all cholesterol bad?
Cholesterol is ferried around the bloodstream in protein molecules known as lipoproteins. "High-density lipoprotein (HDL, or 'good' cholesterol) removes excess cholesterol from the bloodstream and protects the body against heart disease", explains Melanie Raddon, nurse adviser with the British Heart Foundation.
"Low-density lipoprotein (LDL or 'bad' cholesterol), on the other hand, carries cholesterol from the liver to the cells and increases the risk of heart disease."
How does cholesterol increase heart disease risk?
Heart disease occurs when the blood vessels leading to your heart - the coronary arteries - become stiff and narrowed or 'furred' due to the accumulation of a fatty substance called atheroma.
Atheroma is formed when LDL cholesterol is oxidised, the same chemical process that causes apples to go brown when they are exposed to the air. This 'furring' of the arteries is known as atherosclerosis.
How is cholesterol measured?
Cholesterol is measured with a blood test. If your overall cholesterol level is raised, your GP will want to check your LDL and HDL cholesterol levels, as well as measuring blood fats called triglycerides; high levels are also associated with heart disease and stroke.
What's a normal cholesterol level?
In the UK, the average blood cholesterol is about 5.5 to 5.6, which is why heart problems are very common. If you turn that around and ask what is a 'good' cholesterol level the answer is the lower, the better.
Cholesterol is measured in units called millimols per litre of blood (written as mmol/l). There isn't an absolute level at which high cholesterol is diagnosed. It all depends on other risk factors.
What affects my cholesterol level?
The following can all affect your cholesterol levels:
- Physical activity
Does high cholesterol always matter?
For example, if you smoke and have raised cholesterol levels, your risk of heart disease is increased six-fold, if you smoke and have high blood pressure, it is increased nine-fold, if you smoke, have high blood pressure and a raised cholesterol it is increased 16-fold.
If your cholesterol is raised, the doctor will consider other risk factors to calculate your likelihood of having a heart attack.
Other risk factors include:
- Physical inactivity
- Being overweight
- Having diabetes or high blood pressure
What lifestyle changes will help my cholesterol level?
- "Changing to a healthier diet can reduce cholesterol levels by 5-10%," according to Melanie Faddon.
- That means a diet that is low in fat overall, and especially in saturated (animal) fats and transfats (found in some processed foods, such as cakes and pastries).
- Unsaturated fats from foods of plant origin - vegetables, nuts and seeds - and oily fish, reduce levels of 'bad' cholesterol.
- The soluble fibre in fruit and vegetables, such as apples and lentils may help; folic acid found in leafy green vegetables or taken as a supplement may also be useful.
What is the medical treatment?
The main drugs used to lower cholesterol are known as statins, which work by altering enzyme activity in the liver, preventing the manufacture of cholesterol.
According to the British Heart Foundation, there's substantial evidence to show that statins are effective in reducing blood cholesterol levels, so slowing down the development of atherosclerosis and significantly reducing the risk of a heart attack.
Other drugs that may be used to lower cholesterol include fibrates, which lower triglyceride levels.