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About Cholesterol |
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What is cholesterol?
Cholesterol is a fatty substance (a lipid) that is an important part of the outer lining (membrane) of cells in the body
of animals. Cholesterol is also found in the blood circulation of humans. The cholesterol in a person's blood originates
from two major sources, dietary intake and liver production. Dietary cholesterol comes mainly from meat, poultry, fish,
and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin
contain no cholesterol. After a meal, cholesterol is absorbed by the intestines into the blood circulation and is then
packaged inside a protein coat. This cholesterol-protein coat complex is called a chylomicron.
The liver is capable of removing cholesterol from the blood circulation as well as manufacturing cholesterol and
secreting cholesterol into the blood circulation. After a meal, the liver removes chylomicrons from the blood circulation.
In between meals, the liver manufactures and secretes cholesterol back into the blood circulation
Cholesterol: The most common type of steroid in the body, cholesterol has gotten something of a bad name.
However, cholesterol is a critically important molecule. It is essential to the formation of:
- Bile acids (which aid in the digestion of fats)
- Vitamin D
- Progesterone
- Estrogens (estradiol, estrone, estriol)
- Androgens (androsterone, testosterone)
- Mineralocorticoid hormones (aldosterone, corticosterone)
- Glucocorticoid hormones (cortisol)
Cholesterol is also necessary to the normal permeability and function of cell membranes, the membranes that surround cells.
Cholesterol is carried in the bloodstream as lipoproteins. Low-density lipoprotein (LDL) cholesterol is the
"bad" cholesterol because elevated LDL levels are associated with an increased risk of coronary artery (heart) disease.
Conversely, high-density lipoprotein (HDL) cholesterol is the "good" cholesterol since high HDL levels are associated with
less coronary disease.
After the age of 20, cholesterol testing is recommended every 5 years.
A diet high in saturated fats tends to increase the blood cholesterol levels while diets high in unsaturated fats tend to
do the opposite, to lower blood cholesterol levels.
Although some cholesterol is obtained from the diet, most cholesterol is made in the liver and other tissues. The
treatment of elevated cholesterol therefore involves not only diet but also weight loss and regular exercise (and,
occasionally, medications).
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