What is Cholesterol?
Cholesterol -- a white, waxy and odorless substance
-- is a type of lipid,
which is a fat or fatlike substance that doesn't
dissolve in water. This fatty substance is present
in the blood and body tissues, as well as some
foods -- although it's not visible in food. While
cholesterol performs many important functions
in the body, too much of it can cause cardiovascular
disease (heart disease).
There are several different types of cholesterol
in our blood -- some from the food we eat, others
manufactured by the liver:
Total cholesterol
Total cholesterol is not, as many people think, simply the sum of low-density
lipoproteins (LDL cholesterol) and high-density lipoproteins (HDL cholesterol).
Total cholesterol is actually the combination of LDL, HDL and very low-density
lipoproteins (VLDL cholesterol).
LDL cholesterol
LDL cholesterol is also known as the "bad" cholesterol, because excess LDL
cholesterol tends to stick to artery walls, which can, in turn, lead to plaque buildup
and coronary artery disease,
including a heart attack.
The
National Cholesterol Education Program (NCEP)
recommends that people without heart disease
have LDL levels between 130 160 milligrams
per deciliter, depending on their individual
risk factors. In some cases LDL of < 100 milligrams
per deciliter may be recommended when a person
is found to very high risk for a future cardiac
problem. For people who have been diagnosed
with coronary artery disease, the NCEP recommends
their LDL. In many cases, these goals may require
medication and lifestyle changes.
HDL cholesterol
HDL, also known as the "good" cholesterol, helps remove excess cholesterol
from the blood. An abnormally low HDL level (according to the NCEP, anything
below 40 milligrams per deciliter) is considered a risk factor for coronary
artery disease.
VLDL
Very low-density lipoproteins (VLDL) carry
cholesterol and triglycerides from
the liver. After the liver removes triglycerides
from it, VLDL becomes LDL.
Triglycerides
Triglycerides -- compounds made up of fatty acids and glycerol (a carbohydrate)
-- bind to proteins to form VLDL, LDL,
and HDL. The bloodstream carries
these substances to the tissues and stores it for use as future energy. Diet
and exercise affect the blood's triglyceride level. Simple sugars -- such
as fruit juices, alcohol, and sweets -- can dramatically increase triglycerides.
The recommended level of triglyceride level is less than 150 milligrams.
ApoB (Apolipoprotein)
The normal range for apolipoprotein -- the major protein in LDL cholesterol
-- is anything less than 130 milligrams per deciliter. Abnormalties in ApoB
are felt to be an inherited trait. Someone's ApoB level may be elevated even
when his or her LDL cholesterol
is normal, but when both LDL and
ApoB levels are high, the risk for coronary artery disease is higher.
Homocysteine
Increased levels of homocysteine -- an essential amino
acid found in the blood -- and when found to be elevated, can harm the endothelium (the
lining of the arteries). A homocysteine level higher than 12 milligrams per
deciliter is a risk factor for coronary artery disease. Many health care professionals
believe that using folic acid to
lower homocysteine levels may help reduce the risk of heart disease.
Lp(a)
Lp(a) is a lipoprotein like LDL,
except that it has an extra protein that is thought tp interfere with an important
clot-buster in the body. When elevated levels of Lp(a) are deposited in the
walls of the arteries, it may cause blockages to become larger, blood to thicken,
artery walls to stiffen. Genetics -- rather than diet or other lifestyle choices
-- determines Lp(a) levels. People with a high Lp(a) level are at greater risk
for cerebrovascular (involving the brain and the blood vessels supplying it)
and cardiovascular disease, especially if they have a family history of stroke
or early-onset coronary artery disease.
Reviewed by: Joyce Ross, MSN, CRNP
Last updated: November 2005
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