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? 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. Cholesterol | Fatty acids | Triglycerides | Essential part of the cell wall Is used to make bile acids (which help digest fat), vitamin D and hormones Up to 80% is made by the liver and 20% or more comes directly from the food we eat (eggs, liver and kidneys, and shellfish) | Essential part of the cell wall There are two forms:
saturated and unsaturated (mono- and poly-unsaturated) Most are made in the body, but a few need to be taken
from the food we eat (essential fatty acids) Saturated fatty acids are found in meat and are solid at room temperature. Unsaturated fatty acids are found in vegetable products
and are liquid at room
temperature | Essential part of the cell wall Essential energy store:
triglycerides are made up of three fatty acids and therefore contain a lot of fat Make up the majority of the fat stored in your fat tissue Come from the food we eat (meat, dairy and cooking oils) but are also produced
by the body |
 |  |  | | High levels of triglycerides often appear with other well-known risk factors of heart disease, such as high cholesterol and diabetes. |  |
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.
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.
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 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.
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. |