What Is Cholesterol?

Many people are curious about what cholesterol is. Cholesterol is a substance your body uses to hold cells together and to make vitamin D, hormones, and substances that help digest foods. Your body manufactures most of it; the rest comes from animal products, such as meat and whole milk. While your body needs this substance to work properly, too much of it can cause problems.

What Is Cholesterol?

Cholesterol is a soft, waxy substance found in all of your body's cells. Your body needs cholesterol in order to work properly. This is because your body uses it to hold cells together. Your body also uses it to make hormones, vitamin D, and substances that help you digest foods.
 
If too much cholesterol gets into your blood, it can cause problems. This is known as high cholesterol. Other names for high cholesterol include hypercholesterolemia or hyperlipidemia.
 

Sources of Cholesterol

Cholesterol comes from two places. Your body actually makes most of the cholesterol it needs in the liver. The rest of the cholesterol in your body comes from the food you eat.
 
Cholesterol is only made by animals, so you can only get it by eating animal products, such as:
 
  • Chicken
  • Meat
  • Fish
  • Eggs
  • Butter
  • Cheese
  • Whole milk.
     
These foods can provide you with more than enough cholesterol. You will not find cholesterol in anything that comes from a plant. For example, cholesterol-free foods include fruits, vegetables, or whole grains.
 

How Does It Move Through the Blood?

In order to get to all of your cells, cholesterol needs to travel through the bloodstream.
 But because cholesterol is a fat, it separates from the blood similar to the way that oil separates from water. To keep this from happening, proteins form a shell around the cholesterol, making a "cholesterol complex." It is then released into the bloodstream and travels to where it needs to go.
 
A protein that is linked to cholesterol to form this cholesterol complex is called a "lipoprotein." There are two main types of lipoproteins. One is good and the other can be bad, although not always. You have probably heard about "good cholesterol" and "bad cholesterol."
 

What Is LDL Cholesterol?

The cholesterol complex, or lipoprotein, that can be bad is called "LDL." LDL stands for low density lipoprotein. Remember, a lipoprotein is a protein that forms a shell around cholesterol. Normally, LDLs transport cholesterol from your liver and deliver it to the tissues that need it. But if you have a lot of LDLs left over after all of your tissues have been taken care of, the LDLs will "let go" of the extra cholesterol while traveling through your blood. This can cause a buildup of cholesterol known as plaque and lead to a condition called atherosclerosis, or narrowing and hardening of blood vessels.
 

What Is HDL Cholesterol?

The good lipoprotein, which is also known as the "good cholesterol," is called "HDL." HDL stands for high density lipoprotein. HDL cholesterol is "good cholesterol," because it picks up the extra cholesterol that was dropped off by the LDLs and brings it to your liver. This way, your liver can repackage it to use it later, or simply get rid of it.
 
This is why it is good to have high levels of HDL in your system and low levels of LDL. Think of "H" for "high" to help you remember this about HDL. And "L" stands for low, which is a way to remember that you want low levels of LDL.
 

How Is Cholesterol Tested?

The only way to determine your cholesterol level is to have a blood test. According to recent guidelines, a person should get a fasting cholesterol test every five years; however, people with risk factors for heart disease should have their cholesterol tested more frequently.
 
There are several types of tests available. Each test can look at different components of cholesterol and fats in the blood, including:
 
  • Total cholesterol
  • Low density lipoprotein (LDL) -- the "bad" cholesterol
  • High density lipoprotein (HDL) -- the "good" cholesterol
  • Triglycerides.
     
Some cholesterol tests, like a lipid profile done at the doctor's office, will look at all four components. Other tests, like most home cholesterol tests, only look at total cholesterol. Some tests also provide a cholesterol ratio or VLDL (very low density lipoprotein) as part of their results.
 
(Click Cholesterol Test for more information.)
 

Cholesterol Numbers at a Glance

The following table outlines healthy cholesterol levels.
 
Cholesterol Category
Healthy Level
Total Cholesterol
Less than 200 mg/dL
Less than 100 mg/dL, but will depend on the number of risk factors
Greater than 40 mg/dL, but the higher the better
Less than 150 mg/dL
 
(Cholesterol levels are measured in milligrams [mg] of cholesterol per deciliter [dL] of blood.)
 
(Click Cholesterol Levels to learn the guidelines for the different categories.)
 

What Is High Cholesterol?

High cholesterol is a condition that affects 40 million Americans and is one of the risk factors for developing heart disease. Each year, more than a million Americans have heart attacks and about a half-million die from heart disease.
 
(Click High Cholesterol to learn more about this condition.)
 

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Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD
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