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What is cholesterol

Cholesterol is a waxy substance, one of the wide range of fats (lipids) present in the body. It is essential to life.

Cholesterol is an important component of all cell membranes, with about 25% of the body’s total cholesterol in the cell membranes of the nervous system, where it is a major component of the fatty sheaths that insulate nerves.

It also provides the basic skeleton for the synthesis of many hormones – the sex steroids, such as oestradiol and testosterone, the steroid hormones synthesised by the adrenal gland, for example cortisol, as well as the precursor of vitamin D (7-dehydrocholesterol).

Cholesterol is also an essential precursor of the bile acids and is therefore vital to fat digestion. An adult body contains about 150g of cholesterol.


How much cholesterol comes from the diet?

Although nearly all body tissues can synthesise cholesterol, most is synthesised by the liver and intestine. It is therefore naturally present in the blood, irrespective of dietary cholesterol intake. The liver must produce a certain amount of cholesterol - without it the body would cease to function properly. It is estimated that an adult synthesises 0.5-1.0g of cholesterol per day, which is more than would usually be absorbed from the diet.

The total amount of cholesterol in our bodies at any one time will depend on the amounts synthesised and excreted and the amount of dietary cholesterol absorbed. Usually only about one third of the cholesterol in the body comes from the diet.

In most people, body synthesis will decline when more is absorbed from the diet, however some people are unable to regulate cholesterol homeostasis in this way.


Related information

Find out more about LDL and HDL Cholesterol

Cholesterol and CHD

Eggs and cholesterol