Cholesterol

Cholesterol is a fatty substance found in all cell membranes. The nervous system contains about 40% of all the body cholesterol levels. Cholesterol comes in two parts "Chole" = bile and "Sterol" = steroid.

Required by the body for a number of health reasons, unfortunately it has always been given a bad name, namely due to problems associated with high cholesterol levels.

The main functions of cholesterol are:

An excess of cholesterol in the bile can lead to gallstones, and excess in the blood can become deposited on the artery walls leading to Coronary Heart Disease.

There are four main types of lipoproteins all having slightly different structures and functions.

(a) Chylomicroms: Triglyceride - rich particles formed in the intestine from dietary fats.

(b) VLDL (Very low density lipoproteins) - transport triglycerides from the liver to the tissues where it is very easily broken down and the cholesterol used.

(c) LDL (Low density lipoprotein) 20 % protein shell and 80 % triglyderides. They transport the cholesterol from the liver to the tissues. Here it is broken down less easily than the VLDL's and used for cell membrane metabolism and hormone production etc. Excess levels contribute to the formation of atheroma.

(d) HDL (High density lipoprotein) High levels are not associated with atheroma or CHD. HDL's, act as scavengers by removing cholesterol from the blood before it can enter the arterial wall, and returning it to the liver.

Dietary cholesterol only comes from food of animal origin (foods high in dietary cholesterol are egg yolk, cream, full fat milk, cheddar cheese, liver, kidneys and prawns).

However most of the cholesterol in the body does not come from the diet, it is manufactured by the body tissues, particular the liver, because it is an essential component of every cell membrane.

It is also needed for the synthesis of bile acids and a number of hormones, including the steroid sex hormones and Vitamin D.

The following factors all show an effect on cholesterol in the body.