AHA Scientific Position
Cholesterol is a soft, waxy substance found among the lipids
(fats) in the bloodstream and in all your body's cells. It's an
important part of a healthy body because it's used to form cell
membranes, some hormones and is needed for other functions. But
a high level of cholesterol in the blood —
hypercholesterolemia — is a major risk factor for coronary heart
disease, which leads to heart attack.
Cholesterol and other fats can't dissolve in the blood. They
have to be transported to and from the cells by special carriers
called lipoproteins. There are several kinds, but the ones to
focus on are low-density lipoprotein (LDL) and high-density
lipoprotein (HDL).
What is LDL cholesterol?
Low-density lipoprotein is the major cholesterol carrier in
the blood. If too much LDL cholesterol circulates in the blood,
it can slowly build up in the walls of the arteries feeding the
heart and brain. Together with other substances it can form
plaque, a thick, hard deposit that can clog those arteries. This
condition is known as atherosclerosis. A clot (thrombus) that
forms near this plaque can block the blood flow to part of the
heart muscle and cause a heart attack. If a clot blocks the
blood flow to part of the brain, a stroke results. A high level
of LDL cholesterol (160 mg/dL and above) reflects an increased
risk of heart disease. If you have heart disease, your LDL
cholesterol should be less than 100 mg/dL. That's why LDL
cholesterol is called "bad" cholesterol. Lower levels of LDL
cholesterol reflect a lower risk of heart disease.
What is HDL cholesterol?
About one-third to one-fourth of blood cholesterol is carried
by HDL. Medical experts think HDL tends to carry cholesterol
away from the arteries and back to the liver, where it's passed
from the body. Some experts believe HDL removes excess
cholesterol from plaques and thus slows their growth. HDL
cholesterol is known as "good" cholesterol because a high HDL
level seems to protect against heart attack. The opposite is
also true: a low HDL level (less than 40 mg/dL in men; less than
50 mg/dL in women) indicates a greater risk. A low HDL
cholesterol level also may raise stroke risk.
What is Lp(a) cholesterol?
Lp(a) is a genetic variation of plasma LDL. A high level of
Lp(a) is an important risk factor for developing atherosclerosis
prematurely. How an increased Lp(a) contributes to heart disease
isn't clear. The lesions in artery walls contain substances that
may interact with Lp(a), leading to the buildup of fatty
deposits.
What about cholesterol and diet?
People get cholesterol in two ways. The body — mainly the
liver — produces varying amounts, usually about 1,000 milligrams
a day. Foods also can contain cholesterol. Foods from animals
(especially egg yolks, meat, poultry, fish, seafood and
whole-milk dairy products) contain it. Foods from plants
(fruits, vegetables, grains, nuts and seeds) don't contain
cholesterol.
Typically the body makes all the cholesterol it needs, so
people don't need to consume it. Saturated fatty acids are the
main culprit in raising blood cholesterol, which increases your
risk of heart disease. Trans fats also raise blood cholesterol.
But dietary cholesterol also plays a part. The average American
man consumes about 337 milligrams of cholesterol a day; the
average woman, 217 milligrams.
Some of the excess dietary cholesterol is removed from the
body through the liver. Still, the American Heart Association
recommends that you limit your average daily cholesterol intake
to less than 300 milligrams. If you have heart disease, limit
your daily intake to less than 200 milligrams. Still, everyone
should remember that by keeping their dietary intake of
saturated fats low, they can significantly lower their dietary
cholesterol intake. Foods high in saturated fat generally
contain substantial amounts of dietary cholesterol.
People with severe high blood cholesterol levels may need an
even greater reduction. Since cholesterol is in all foods from
animal sources, care must be taken to eat no more than six
ounces of lean meat, fish and poultry per day and to use
fat-free and low-fat dairy products. High-quality proteins from
vegetable sources such as beans are good substitutes for animal
sources of protein.
How does physical activity affect cholesterol?
Regular physical activity increases HDL cholesterol in some
people. A higher HDL cholesterol is linked with a lower risk of
heart disease. Physical activity can also help control weight,
diabetes and high blood pressure. Aerobic physical
activity raises your heart and breathing rates. Regular moderate
to intense physical activity such as brisk walking, jogging and
swimming also condition your heart and lungs.
Physical inactivity is a major risk factor for heart
disease. Even moderate-intensity activities, if done daily,
help reduce your risk. Examples are walking for pleasure,
gardening, yard work, housework, dancing and prescribed home
exercise.
How does tobacco smoke affect cholesterol?
Tobacco smoke is one of the six major risk factors of heart
disease that you can change or treat. Smoking lowers HDL cholesterol
levels and increases the tendency for blood to clot.
How does alcohol affect cholesterol?
In some studies, moderate use of alcohol is linked with
higher HDL cholesterol levels. However, because of other risks,
the benefit isn't great enough to recommend drinking alcohol if
you don't do so already.
If you drink, do so in moderation. People who consume
moderate amounts of alcohol (an average of one to two drinks per
day for men and one drink per day for women) have a lower risk
of heart disease than nondrinkers. However, increased
consumption of alcohol brings other health dangers, such as
alcoholism, high blood pressure, obesity, stroke, cancer,
suicide, etc. Given these and other risks, the American Heart
Association cautions people against increasing their alcohol
intake or starting to drink if they don't already do so.
Consult your doctor for advice on consuming alcohol in
moderation.
Related Scientific Statements
Cholesterol
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