Cholesterol : Introduction, Functions & Types

• Cholesterol is a type of lipid.
• Cholesterol is a waxy, fat-like substance that your liver produces naturally.
• It is an oil-based substance which does not mix with the blood, that is water-based. It travels around the body in lipoproteins.
• Our body needs some cholesterol to make hormones, vitamin D, and substances that help us digest foods, which our body makes as it needs.
• It comes from two sources. Our liver makes all the cholesterol we need. The remainder of it in our body comes from foods derived from animals. For example, meat, poultry and full-fat dairy products all contain cholesterol, called dietary cholesterol.
• The liver produces 75% of the it that circulates in our blood. The other 25% comes from food.
• At normal levels, it actually plays an important role in helping cells do their jobs. Cholesterol content in the bloodstream is regulated by the liver. After a meal, cholesterol in the diet is absorbed from the small intestine and metabolized and stored in the liver. As the body requires it, it may be secreted by the liver. When too much cholesterol is present in the body, it can build up in deposits called plaque along the inside walls of arteries, causing them to narrow.
• It is both good and bad. At normal levels, it is an essential substance for the body. However, if concentrations in the blood get too high, it becomes a silent danger that puts people at risk of heart attack. Risk factors for high cholesterol include family history and the modifiable lifestyle choices of diet and exercise.
• Having high cholesterol does not usually produce any symptoms. If lifestyle changes are unsuccessful or cholesterol levels are very high, a doctor may prescribe a lipid-lowering drug, such as a statin.

Functions of Cholesterol

It has four primary functions, without which we could not survive.
These are:

• contributing to the structure of cell walls
• making up digestive bile acids in the intestine
• allowing the body to produce vitamin D
• enabling the body to make certain hormones

What are the Different Types of Cholesterol?

It does not travel freely through the bloodstream. Instead, it is attached or carried by lipoproteins (lipo = fat) in the blood. There are three types of lipoproteins that are categorized based upon how much protein there is in relation to the amount of cholesterol.
Low-density lipoproteins (LDL) contain a higher ratio of cholesterol to protein and are thought of as the “bad” cholesterol. Elevated levels of LDL increases the risk of heart disease, stroke, and peripheral artery disease, by causing plaque along inside of artery walls. Over time, as plaque buildup (plaque deposits) increases, the artery narrows (atherosclerosis) and blood flow decreases. If the plaque ruptures, it can cause a blood clot to form that prevents any blood flow. This clot is the cause of a heart attack or myocardial infarction if the clot occurs in one of the coronary arteries in the heart.
High-density lipoproteins (HDL) are made up of a higher level of protein and a lower level of cholesterol. These tend to be thought of as “good” cholesterol. The higher the HDL to LDL ratio, the better it is for the individual because such ratios can potentially be protective against heart disease, stroke, and peripheral artery disease.
Triglycerides (a type of fat) may increase cholesterol-containing plaques if levels of LDL are high and HDL are low.
Total cholesterol score is the sum of HDL , LDL and 20% of triglycerides as determined by a blood test. A high score indicates an increased risk for developing cardiovascular disease and/or strokes.

LDL (Bad Cholesterol)

Low-density lipoprotein (LDL) is often called “bad cholesterol.” If our levels of LDL are too high, it can build up on the walls of our arteries. The buildup is also known as cholesterol plaque. This plaque can narrow our arteries, limit our blood flow, and raise our risk of blood clots. Elevated levels of LDL increase the risk of heart disease, stroke, and peripheral artery disease, by causing plaque along inside of artery walls. Over time, as plaque buildup (plaque deposits) increases, the artery narrows (atherosclerosis) and blood flow decreases. If the plaque ruptures, it can cause a blood clot to form that prevents any blood flow. This clot is the cause of a heart attack or myocardial infarction if the clot occurs in one of the coronary arteries in the heart.

HDL (Good Cholesterol)

High-density lipoprotein (HDL) is often called “good cholesterol.” It helps return LDL to our liver to be removed from our body. This helps prevent cholesterol plaque from building up in our arteries.
When we have healthy levels of HDL , it can help lower our risk of blood clots, heart disease, and stroke.
High-density lipoproteins (HDL) are made up of a higher level of protein and a lower level of cholesterol. The higher the HDL to LDL ratio, the better it is for the individual because such ratios can potentially be protective against heart disease, stroke, and peripheral artery disease.

Triglycerides (a Different Type of Lipid)

Triglycerides are another type of lipid. They’re different from cholesterol. While our body uses cholesterol to build cells and certain hormones, it uses triglycerides as a source of energy.
When we eat more calories than our body can use right away, it converts those calories into triglycerides. It stores triglycerides in our fat cells. It also uses lipoproteins to circulate triglycerides through our bloodstream.
If we regularly eat more calories than our body can use, our triglyceride levels can get high. This may raise your risk of several health problems, including heart disease and stroke.
Our doctor can use a simple blood test to measure our triglyceride level, as well as our cholesterol levels.

Why Cholesterol Matters?

It circulates in the blood. As the amount of it in our blood increases, so does the risk to our health. That’s why it’s important to have our cholesterol tested, so we can know your levels.
There are two types of cholesterol: LDL, which is bad, and HDL, which is good. Too much of the bad kind, or not enough of the good kind, increases the risk that it will slowly build up in the inner walls of the arteries that feed the heart and brain. It can join with other substances to form a thick, hard deposit on the inside of the arteries. This can narrow the arteries and make them less flexible – a condition known as atherosclerosis. If a blood clot forms and blocks one of these narrowed arteries, a heart attack or stroke can result.

Cholesterol in Food

Cholesterol-rich foods, like eggs, shrimp, and lobster are no longer completely forbidden. Research shows that the cholesterol we eat has only a small effect on blood cholesterol levels for most people. A few people are "responders," whose blood levels spike up after eating eggs. But for most, saturated fat and trans fats are bigger concerns. Daily cholesterol limits are 300 mg for healthy people and 200 mg for those at higher risk. One egg has 186 mg of it.