High-density lipoprotein, also called HDL, and low-density lipoprotein, or LDL, together with triglycerides make up your total cholesterol levels. It's important to know your HDL and LDL levels in addition to your total cholesterol, because HDL can benefit your blood vessels and decrease the risk of heart disease while LDL can cause harm and lead to heart disease.
Purpose
Cholesterol, a waxy substance that performs valuable functions within your body, is carried on LDL from the liver to cells, where it's used for energy. Many experts believe that HDL cleans the arteries of excess cholesterol not used by your cells, taking it back to the liver. When there isn't enough HDL, which makes up around 25 to 33 percent of total cholesterol, to keep up with the LDL's transport of cholesterol from the liver, deposits of LDL, called plaque, stick to the walls of blood vessels.
Sources
Your body manufactures most of the cholesterol in your body, around 75 percent, the American Heart Association reports, in your liver and other cells. Only 25 percent of cholesterol comes from dietary sources. This explains why people who eat well, don't smoke and are of normal weight can still have elevated cholesterol levels and be at risk for developing heart disease.
Normal Levels
Your HDL should stay above 40 milligrams per deciliter, or mg/dL, the American Heart Association advises. Keeping your HDL above 60 mg/dL or more appears to protect the heart against disease, Clemson Cooperative Extension explains. Staying below the optimal level for LDL, less than 100 mg/dL, also reduces the risk of heart disease.
Risk Factors
People who have a hereditary variant of LDL called LD(a) have higher than normal levels of LDL. Other risk factors for high total cholesterol and LDL include smoking, obesity, inactivity, diabetes and eating a diet high in saturated and trans fats.
Dangers
LDL builds up on the interior walls of blood vessels, forming plaque. Plaque damages and irritates the blood vessel walls, sometimes causing blood clots to form at the site. Plaque can decrease the lumen of the blood vessels, reducing the amount of blood that passes through. Blood clots that form around plaque can break off, travel through the blood vessel and lodge somewhere else, possibly causing a stroke from decreased blood flow to the brain or causing a heart attack by reducing blood flow to the heart.
Prevention
Dietary measures and lifestyle changes help lower total cholesterol and LDL and raise HDL. Consuming omega-3 fatty acids in place of saturated fats lowers triglyceride and LDL levels while raising HDL levels. Medications to lower LDL, such as statins, also decrease the risk of heart disease.
