is a substance which naturally occurs in animal tissue
and fat. It can be synthesized in the liver and is a normal
component of bile, which is used in digestion. Cholesteral
is also essential for the body to produce various hormones.
Only about 20 percent of the cholesterol in our bodies comes
from diet; the other 80 percent is synthesized by the liver.
However, excess cholesterol in the diet
can lead to an increased risk of developing heart disease
and other conditions. For example, atherosclerosis
is a condition in which cholesterol deposits build up inside
arteries, reducing or blocking blood flow. Additionally, if
an arterial deposit breaks loose, it can travel through the
blood stream until it lodges in a narrow blood vessel, blocking
bloodflow. If the blockage prevents blood flow to the heart,
it can cause a heart attack. If the blockage prevents blood
flow to the brain, it can cause a stroke.
Cholesterol is often subdivided into two
categories: high-density lipoprotein (HDL) cholesterol and
low-density lipoprotein (LDL) cholesterol. Elevated levels
of LDL or "bad" cholesterol is associated with heart disease
but HDL or "good" cholesterol helps retrieve accumulating
LDL and return it to the liver for disposal. Thus, having
a low "total" cholesterol level may be less desirable than
having a high level of protective HDL and a low level of LDL
Cholesterol levels can be reduced by restricting
the amount of fat in the diet and by exercising regularly.
Smoking and diabetes each lower the level of HDL or "good"
cholesterol in the body. High blood pressure also accentuates
the effects of cholesterol buildup. After menopause, women's
HDL levels may drop unless they take hormone
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain