Cholesterol performs a number of vital functions in the body, including playing a part in the synthesis of hormones such as estrogen and testosterone as well as vitamin D. Cholesterol, a waxy substance, isn't water soluble and can't travel through your bloodstream on its own. High-density lipoproteins or HDL are a type of lipoprotein, substances that transport cholesterol and fats through the bloodstream.
Definition
High-density lipoprotein is often called the "good" cholesterol, but that may be too simplistic, Harvard Health Publications says. There are actually several types of HDL that have different shapes and different roles to play. All lipoproteins come from two sources: the food you eat and from your own body's production in the liver and other cells, which accounts for 75 percent of your cholesterol level, according to the American Heart Association.
Purpose
High-density lipoprotein has more functions than originally thought, Harvard Health Publications reports. High-density lipoprotein removes cholesterol from artery walls, where it can cause atherosclerosis, buildup of plaque in the inside of the artery walls. This narrows the blood vessels, making it more difficult for blood and oxygen to reach organs and cells. The lipoprotein also removes cholesterol from low-density lipoprotein, or LDL, which carries cholesterol from the liver and often deposits on artery walls. However, some HDL particles carry cholesterol into LDL. High-density lipoprotein also decreases inflammation that contributes to atherosclerosis in artery walls and relaxes blood vessels, which increases their diameter and increases blood flow.
Normal Levels
Normal levels of HDL should be above 40 milligrams per deciliter for men and 50mg/dL for women. Optimal levels for HDL in men and women is 60mg/dL or higher. The mean HDL cholesterol level in adults older than 20 in the United States is 54.3, the AHA says.
Increasing HDL
You can increase your HDL levels by not smoking; quitting smoking can increase your HDL levels by up to 10 percent, MayoClinic.com says. Starting an exercise program if you've been sedentary can raise your HDL levels about 5 percent, also according to MayoClinic.com. Losing as little as 5 percent to 10 percent of your weight if you're obese can also raise HDL levels. Each 6 lbs. you lose, your HDL can increase by 1mg/dL, the Mayo Clinic website adds.
Considerations
When it comes to cholesterol levels, it's most important to concentrate first on lowering LDL cholesterol, the "bad" cholesterol, Harvard Health Publications says. Many of the same actions that raise HDL levels lower LDL cholesterol levels, such as eliminating trans fats, a type of saturated fat, from your diet. Some medications that lower LDL levels also raise HDL levels, such as niacin, statins and fibrates.
