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What is Cholesterol?

Cholesterol is a waxy, fat-like substance that the body uses to form cell membranes and certain hormones. It’s essential for normal body function, but the body produces all the cholesterol it needs on its own. Any cholesterol in diet is extra, and the body deposits this surplus in the blood vessels. This surplus can eventually lead to narrowing of the arteries, stroke and heart disease. In fact, high blood cholesterol is a major risk factor for heart disease (mainly derived from animal fats in the diet), which is the leading cause of death, specifically in the United States. About 17% of American adults have atherosclerosis and high blood cholesterol, and even children can develop it.

The 2 Types of Cholesterol

Low-Density Lipoproteins (LDL)

- A lipid that is necessary for supporting the membranes of the cells in the body. Because cholesterol cannot dissolve or be absorbed directly, LDLs are necessary. When the body senses that there is a cholesterol in the blood, LDL is released into the blood stream. These low density lipoproteins then locate and transport cholesterol throughout the body.

- LDL cholesterol is what can build up on the walls of the arteries, making them hard and narrow. Narrowing of the arteries can cause coronary artery disease, heart attack and stroke.-LDL is made naturally by the body. Depending on genetics, some people may have more LDL than others.

- LDL is considered to be the "bad" type of cholesterol.

High-Density Lipoproteins (HDL)

- A lipoprotein that scours the bloodstream in search for stray LDL cholesterol and transports them back to the liver where they can be reused. HDL cholesterol acts as a maintenance crew for the inner walls of blood vessels (endothelium). Damage to the endothelium is the first step in the process of atherosclerosis, which causes heart attacks and strokes. HDL chemically scrubs the endothelium clean and keeps it healthy.

- HDL circulates through your body, acting like a cholesterol magnet. It gathers up the bad cholesterol and moves it out of the arteries. HDL is desired and helps lower the risk of atherosclerosis. HDL acts as a kind of "hall monitor" to find and eliminate bad cholesterol where it shouldn't be in the bloodstream.

- HDL cholesterol is referred to as “good cholesterol.”

Approximately 50 percent of the weight of an LDL particle is cholesterol and only 25% is protein. HDL particles, on the other hand, consist of 20% cholesterol by weight and 50% protein. Since protein is more dense than fat, HDL particles are more dense than LDL particles, hence the names "high-density" and "low-density" lipoproteins.

WHY ARE HDL AND LDL MONITORED?

Doctors monitor the concentrations of LDL and HDL in the blood of a patient in order to determine and evaluate a patient's health if the patient is at risk for a disease, specifically heart disease. The hardening of the arteries makes the arteries more narrow, making it harder for blood to travel to the heart, which would then lead to strokes and heart attacks. Doctors measure the concentration of HDL in order to ensure that there are high enough levels of it to promote good cardiovascular health as HDL carries cholesterol away from the cells and towards the liver, counteracting the actions of LDL. According to the American Heart Association (AHA), HDL levels should be at least 40 mg/dL, and optimally higher than 60 mg/dL, while LDL levels should be lower than 129 mg/dL for the majority of people, and even lower for those at risk for heart disease.


Other molecules monitored along with LDL and HDL in a patient's blood include triglycerides, low density lipoproteins, and high density lipoproteins. Triglycerides are a type of fat found in the bloodstream inside of cholesterol molecules, therefore, high levels of triglyceride increase the risk for heart disease. Excess LDL is an important indicator for heart disorders. Likewise, a low level of HDL is also a significant factor in determining a persons risk for developing heart disease.

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What Do the Results Of A Cholesterol Test Mean?

- For a patient's total blood cholesterol level, these are the possible results and their meaning. The higher a patient's total blood cholesterol level is, the greater risk they have for coronary heart disease. When at a high risk (240 mg/dL and above), the patient has more than twice the risk for coronary heart disease than a patient with a desirable measure of total blood cholesterol level.


- For a patient's HDL cholesterol level, these are the possible results and their meaning. When looking at HDL cholesterol level, higher levels are better. A high HDL level means that a patient's is at a lower risk for heart disease and is considered safe against heart disease.


- For a patient's LDL cholesterol level, these are the possible results and their meaning. The lower a patient's LDL cholesterol level is, the lower risk they have of heart attack and stroke.


- For a patient's triglyceride level, these are the possible results and their meaning. When looking at triglyceride level, lower levels are better as high triglyceride levels suggest lifestyle-related risk factor, such as physical inactivity, cigarette smoking, and a diet very high in carbohydrates. However, high triglyceride levels may also be caused by diseases and genetic disorders.

What Can Patients Do?

In order to change the levels of LDL and HDL in their blood, patients can begin to maintain a diet that is low in sodium and fats. Incorporating various fruits and vegetables into their diet can also have positive results.

  • Stop or don't smoke
  • Lose weight
  • Increase heart rate commonly
  • Choose healthier fats
  • Do not drink alcohol

This change in diet will increase HDL levels in the blood while reducing LDL levels. Reducing the amount of saturated fats and sodium can also result in the reduction of LDL and an increase in HDL. Physical activity and exercise for 30 minutes a day 5 days a week, can also increase HDL levels and decrease LDL levels.

Fats to Avoid

Avoiding saturated fats and trans fats will help to lower total cholesterol as well as the LDL levels. However, the opposite is also true. Eating a diet containing many saturated and/or trans fat will also raise total cholesterol and LDL cholesterol. Trans fat causes an exponential rise in heart attacks because they stick to the blood vessels hindering healthy blood flow. A diet high in saturated fats is the main cause of high-blood cholesterol levels, but an overall high-cholesterol diet can also raise cholesterol levels.

Citations/Resources

  1. WebMD (n.d.). LDL Cholesterol: “The Bad Cholesterol”. Retrieved from http://www.webmd.com/cholesterol-management/ldl-cholesterol-the-bad-cholesterol
  2. WebMD (n.d.). HDL Cholesterol: “The Good Cholesterol”. Retrieved from http://www.webmd.com/cholesterol-management/hdl-cholesterol-the-good-cholesterol
  3. WebMD (n.d.). Heart Disease and Lowering Cholesterol. Retrieved from http://www.webmd.com/heart-disease/guide/heart-disease-lower-cholesterol-risk
  4. Kamps, A. (n.d.). How Do LDL and HDL Differ Structurally and Functionally? Retrieved from http://healthyeating.sfgate.com/ldl-hdl-differ-structurally-functionally-2003.html
  5. How High Cholesterol Leads to Atherosclerosis. (n.d.). Retrieved from http://www.webmd.com/cholesterol-management/how-high-cholesterol-leads-atherosclerosis