More on cholesterol

Millions of people around the world have high cholesterol (also known as
dyslipidaemia). High cholesterol increases the risk of heart attacks and strokes. But what are cholesterol?

What are lipids?

The body contains three basic types of fats (or lipids): cholesterol, fatty acids and triglycerides. These fats are needed by the body to function properly, but high levels can cause health problems. The table below summarises some of the characteristics of cholesterol, fatty acids and triglycerides.

What are lipoproteins?

Cholesterol is an essential part of all cell walls so it is needed throughout the body. But like oil and water, cholesterol and blood don’t mix. To get around this problem the body packages cholesterol into tiny molecules called lipoproteins, which are made up of a combination of fat and protein. The lipoprotein provides a protective wrapping for the cholesterol allowing it to be transported around the body in the blood. They also act like an address label that helps the body to direct the cholesterol to specific destinations.

What is the difference between good (HDL) and bad (LDL) cholesterol?

There are several types of lipoproteins that differ structurally in the amount of protein and fat they contain. The more fat there is in the lipoprotein the lower
the density of it. The four main types of lipoprotein are:

Although the main role of lipoproteins is to transport cholesterol and fats around the body they all have slightly different functions.

LDL

Virtually every cell in the body is able to take up and use the cholesterol that LDL carries. But usually there are more LDL particles in the blood than your body can use. Your liver’s job is to remove excess LDL from the blood and use it to make more bile acid or new lipoproteins. Sometimes your body can’t keep up with this and the LDL particles start to gather in the lining of your blood vessels. If this continues to happen then fatty plaques can develop, which can have a devastating impact on your health. Fatty plaques are associated with an increased risk of heart attacks and strokes. LDL is therefore sometimes referred to as ‘bad’ cholesterol.

HDL

HDL particles are quite different to LDL (bad) cholesterol. They have lots of
protein and not much fat. HDL has two main functions: they supply
chylomicrons and VLDLs with the proteins that signal the liver to trap them and take out their fat; and they also sponge up excess cholesterol from the lining of blood vessels and carry it to the liver where it is got rid of from the body. Because HDL removes cholesterol from the blood and therefore can reduce the risk of fatty plaques developing it is sometimes known as ‘good’ cholesterol.

Chylomicron and VLDL

Your intestines absorb fat from the foods that you eat. The fat molecules are
broken down into fatty acids before being assembled into new triglyceride
molecules and packaged along with a small amount of cholesterol into
chylomicrons. At the same time, your intestines are also absorbing sugars and proteins from your food. These are also converted into triglyceride molecules and packaged along with cholesterol and proteins into VLDLs (very low-density lipoproteins).

As chylomicrons and VLDLs move around the body they temporarily stick to the blood vessel walls in muscle that needs energy or in fatty tissue that stores energy. As chylomicrons and VLDLs give up their triglycerides to the parts of the body that needs them they turn into LDLs (low-density lipoproteins). LDLs carry most of the body’s cholesterol (60–70%).

You can learn more about how high cholesterol can affect your health here.