Cholesterol
by Eleanor Mayfield
Cholesterol is sort of a "cousin" of fat. Both fat and cholesterol
belong to a larger family of chemical compounds called lipids. All
the cholesterol the body needs is made by the liver.
It is used to build cell membranes and brain and nerve tissues. Cholesterol
also helps the body produce steroid hormones needed for body regulation,
including processing food, and bile acids needed for digestion.
People don't need to consume dietary cholesterol because the body
can make enough cholesterol for its needs. But the typical U.S. diet
contains substantial amounts of cholesterol, found in foods such as
egg yolks, liver, meat, some shellfish, and whole-milk dairy products.
Only foods of animal origin contain cholesterol.
Cholesterol is transported in the bloodstream in large molecules
of fat and protein called lipoproteins. Cholesterol carried in low-density
lipoproteins is called LDL-cholesterol; most cholesterol is of this
type. Cholesterol carried in high-density lipoproteins is called HDL-cholesterol.
A person's cholesterol "number" refers to the total amount of cholesterol
in the blood. Cholesterol is measured in milligrams per deciliter
(mg/dl) of blood. (A deciliter is a tenth of a liter.) Doctors recommend
that total blood cholesterol be kept below 200 mg/dl. The average
level in adults in this country is 205 to 215 mg/dl. Studies in the
United States and other countries have consistently shown that total
cholesterol levels above 200 to 220 mg/dl are linked with an increased
risk of coronary heart disease. (See "Lowering Cholesterol" in the
March 1994 FDA Consumer.)
LDL-cholesterol and HDL-cholesterol act differently in the body.
A high level of LDL-cholesterol in the blood increases the risk of
fatty deposits forming in the arteries, which in turn increases the
risk of a heart attack. Thus, LDL-cholesterol has been dubbed "bad"
cholesterol.
On the other hand, an elevated level of HDL-cholesterol seems to
have a protective effect against heart disease. For this reason, HDL-cholesterol
is often called "good" cholesterol.
In 1992, a panel of medical experts convened by the National Institutes
of Health (NIH) recommended that individuals should have their level
of HDL-cholesterol checked along with their total cholesterol.
According to the National Heart, Lung, and Blood Institute (NHLBI),
a component of NIH, a healthy person who is not at high risk for heart
disease and whose total cholesterol level is in the normal range (around
200 mg/dl) should have an HDL-cholesterol level of more than 35 mg/dl.
NHLBI also says that an LDL-cholesterol level of less than 130 mg/dl
is "desirable" to minimize the risk of heart disease.
Some very recent studies have suggested that LDL-cholesterol is more
likely to cause fatty deposits in the arteries if it has been through
a chemical change known as oxidation. However, these findings are
not accepted by all scientists.
The NIH panel also advised that individuals with high total cholesterol
or other risk factors for coronary heart disease should have their
triglyceride levels checked along with their HDL-cholesterol levels.
Food and Drug
Administration Publication No. (FDA) 99-2286
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