Which type of lipid is considered "bad" cholesterol?

Low-density lipoprotein (LDL) is often referred to as "bad" cholesterol because of its association with an increased risk of cardiovascular disease. LDL transports cholesterol from the liver to cells throughout the body. However, when there is an excess of LDL in the bloodstream, it can lead to the buildup of cholesterol in the walls of arteries, which contributes to the formation of plaques. This process can narrow the arteries and restrict blood flow, leading to conditions such as atherosclerosis, heart attacks, or strokes.

In contrast, high-density lipoprotein (HDL) is considered "good" cholesterol because it helps remove excess cholesterol from the bloodstream and transports it back to the liver for excretion or recycling. Triglycerides, while also a type of lipid, are primarily a storage form of fat in the body and are not categorized specifically as "good" or "bad" cholesterol in the same manner. Cholesterol esters are another form of cholesterol that are involved in various physiological functions, but they do not carry the same negative connotation as LDL.

Thus, LDL is categorized as "bad" cholesterol due to its role in promoting cardiovascular disease when present in high levels.