Cholesterol: A waxy, fatlike substance, classified as a lipid and found in all tissues in humans and other animals. It is thus in all foods from animal sources—meat, eggs, fish, poultry, and dairy products. No plant-derived food contains cholesterol. Cholesterol is essential to life. It is part of all cell membranes, certain hormones, vitamin D, and other substances. The body makes all the cholesterol it needs; you don’t need to consume any to stay healthy.
Lipoproteins: Packages of proteins, cholesterol, and triglycerides, assembled by the liver and circulating in the blood.
LDL, or low-density lipoprotein carries cholesterol through the bloodstream, dropping it off where it is needed for cell building—and leaving any unused residue of cholesterol in the arterial walls. Since it takes cholesterol into the system, LDL is referred to as bad cholesterol. It can be oxidized (combine with oxygen) in the bloodstream, and that may enhance its ability to produce the artery-blocking plaques that can lead to heart attack.
HDL, or high-density lipoprotein, as it circulates in the bloodstream, picks up cholesterol and brings it back to the liver for reprocessing or excretion. Because HDL clears out cholesterol, it is referred to as good cholesterol.
Triglycerides: These fats circulate in the bloodstream along with cholesterol and other lipids. They come from the food we eat; they are the body’s stored form of fat. Thus when people say, “I’m too fat,” you might say their triglycerides are showing. The body can also assemble triglycerides in the liver.