Cholesterol can be a confusing topic. Your body needs some cholesterol to function properly, but too much of it can increase your risk of heart disease. In addition, cholesterol is often referred to as "good" or "bad" cholesterol. To understand cholesterol, it's important to recognize the different types of lipoproteins and how cholesterol travels through your body.
Lipoprotein Density
Because cholesterol is a lipid, it's hydrophobic, which means that it can't mix with water. Because blood contains a large percentage of water, cholesterol must travel through the blood in a transport mechanism called a lipoprotein. The outer layer of a lipoprotein contains proteins and phospholipids, which are a type of lipid that contain a phosphorus group, according to "Nutrition and You" by Joan Salge Blake. This layer allows the lipoprotein to travel efficiently throughout your blood. The outer layer covers an inner layer that consists mostly of cholesterol and other hydrophobic substances. The higher the amount of protein a lipoprotein contains, the greater its density.
LDL
LDL, or low-density lipoprotein, contains a large percentage of cholesterol and a small percentage of protein. LDLs travel throughout your blood and deposit cholesterol where it's needed in order to allow your body to perform its functions. Because of the high percentage of cholesterol in an LDL, some cholesterol also becomes deposited on the walls of your arteries, according to the National Heart, Lung and Blood Institute. If your blood contains a large amount of LDLs, the amount of cholesterol on your arterial walls accumulates significantly. This promotes atherosclerosis, or a thickening and hardening of the arteries. This increases your risk of heart disease, heart attack and stroke. LDL is often referred to as bad cholesterol.
HDL
HDL, or high-density lipoprotein, contains a large percentage of protein and only a small amount of cholesterol. "Nutrition and You" by Joan Salge Blakes notes that the protein component of HDL allows the lipoprotein to pick up excess cholesterol from the blood and carry it back to the liver, where it can be removed from the body. Because HDL removes excess cholesterol from the blood, the American Heart Association considers high levels of HDL to be protective against heart disease. HDL is often referred to as good cholesterol.
Lipoprotein Values
Ideal LDL levels are less than 100mg/dL of blood. If you're at an especially high risk of heart disease or have existing heart disease, aim to keep your LDL levels below 70mg/dL. Because HDL is protective against heart disease, higher amounts of HDL in the blood are ideal. MayoClinic.com says you should aim to keep your HDL levels above 60mg/dL.
References
- National Heart, Lung and Blood Institute: What are Lipoproteins?
- "Nutrition and You"; Joan Salge Blake; 2008
- MayoClinic.com: High Cholesterol: Tests and Diagnosis
