Cholesterol
is a substance found in the blood. It is made in the liver and is needed
for healthy cell membranes.
However, too much cholesterol in the blood increases the risk of heart disease, and of diseased arteries.
Good and bad cholesterol
The bloodstream transports cholesterol around the body attached to proteins. The combination of cholesterol and protein is called lipoprotein, and there are two types.
- Low-density lipoproteins - LDLs - carry cholesterol from the liver to the cells.
- High-density lipoproteins - HDLs - carry excess cholesterol back to the liver.
LDLs are often called bad cholesterol
because they lead to fat building up on artery walls, which causes
heart disease. HDLs are often called good cholesterol because
they help to stop fat building up in the arteries. |
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| The walls of
healthy arteries should be smooth, without fatty deposits to block them |
Improving the balance
A high proportion of HDLs to LDLs is good for a healthy heart. Monounsaturated and polyunsaturated oils - as found in vegetable oils - help to reduce cholesterol levels in the blood, and also increase the proportion of HDLs compared with LDLs. Check your understanding of such oils by looking at Vegetable oils.
There are also drugs, such as statins, that
can improve high blood pressure and high cholesterol levels.
[ This page has been adapted from www.bbc.co.uk/schools/gcsebitesize/science ]