Cholesterol is often painted as the villain of the piece where general health is concerned, but in fact this soft, waxy substance is a vital body fat (the generic medical term is “lipid”) that is crucial to the functioning of your body’s cells as a source of energy and is transported around your body in your bloodstream.

Contrary to widespread belief (due to the emphasis on diet and cholesterol levels) only a small amount of the cholesterol in your blood is derived from the food you eat. Most of it is created by your liver. The fats you ingest from food (especially meat and dairy produce) are in the form of triglycerides which are mostly stored as fat on you, though low levels are also present in your blood.

In common with all fats, cholesterol is not soluble in water and cannot therefore be carried by directly the bloodstream. What happens is that it combines with proteins to form what are called lipoproteins which are soluble. There are various types od lipoprotein, labelled according to the density of protein in relation to lipid, and all are classed under the generic label “cholesterol”.

VLDL (very low density lipoprotein)

These (and a class of lipoprotein particles called chylomicrons) form only a small faction of your total cholesterol, however they are abundant in triglycerides which they transport to tissues requiring them.

LDL (low-density lipoprotein)

These form the bulk (some 70%) of the cholesterol transported around your body. An LDL particle has a low density of protein and therefore consists largely of lipids (fat). The principal function of LDL is to carry energy (as cholesterol) from the liver to your body’s cells. However, an excess of LDL in the bloodstream results in a build up of fatty deposits that over time restrict blood flow through your main arteries and blood vessels and hence LDL has come to be known as “bad cholesterol”.

The truth is that LDL is in fact a “good thing” but that you can have too much of a good thing, and it’s that which is a “bad thing”. Clear now?

HDL (high-density lipoprotein)

A much smaller (though significant) amount of cholesterol is in the form of HDL (unlike LDL these particles are mostly protein with little fat). These perform the return journey, soaking up excess cholesterol from tissues and artery walls, and transporting it back to the liver to be re-metabolised (or disposed of).

To maintain symmetry, HDL is referred to as “good cholesterol” since it mops up LDL (”bad”) cholesterol. It tends to be higher in women and can be increased through taking physical exercise.

Ideal concentrations for the various forms of cholesterol in your blood are:

Total cholesterol: less than 5.0 mmol/L
LDL cholesterol: less than 3.0 mmol/L
HDL cholesterol: more than 1.0 mmol/L

In general you should aim not only for a low total cholesterol level but for a relatively high level of HDL compared to a relatively low level of LDL (i.e. LDL 2.6 with HDL 1.3 – check here for more information about cholesterol levels).