text: what is cholesterol?is there a good one and a bd one? is it really true some foods can raise your bad cholesterol and others lower it.  some say ,eating oatsmeal can help lower bad cholesterol-are all this true, or just marketing tricks? cholesterol is a certain lipid used for various causes in the organism: it is a major constituent of membranes, a precursor of bile acids, steroid hormones etc.  the terms "bad" and "good" cholesterol reffer not to cholesterol itself ('cause chemically it is all the same), but the vehicles by which it is transported in the blood stream. the are two major types of cholesterol vehicles: ldl (low density lipoproteins) and hdl (high density lipoproteins). hdl transport cholesterol from organs and tissues to the liver, which excrets it. therefore, higher levels of hdl are "good", since they help to get rid of excess cholesterol. ldl, on the other hand, transport cholesterol from the liver to various organs and tissues. of course, it is a necessary function, but if there's too much ldl, it is "bad", since, simply speaking, it packs vascular walls with cholesterol, which ultimately leads to cardiovascular diseases.  it is not quite clear whether cholesterol rich foods really increase the "bad" ldl levels. however, it is very likely that if you eat oatmeal instead of a ribeye steak, your bad cholesterol levels will go down, since plant-derived products do not contain cholesterol. cholesterol is found only in animal products (meat, eggs, dairy).