HDL and LDL:
The 'good' and 'bad' cholesterol myth
'Good' and 'bad' cholesterol
Let us scotch a myth: There is no such thing as 'good' and 'bad' cholesterol; HDL cholesterol and LDL cholesterol. Cholesterol is just one chemical compound and all cholesterol is exactly the same. Talking of LDL cholesterol and HDL cholesterol as if they were two different types of cholesterol is misleading.
Cholesterol is not water soluble so it cannot travel freely on its own in the bloodstream to where it is needed. Cholesterol is transported in little packets together with other materials, notably fats and proteins as the graphic of LDL shows.
These little packets are called lipoproteins, a contraction of the words 'lipid' (a class of substances which includes fats, cholesterol and waxes) and protein. LDL stands for Low-Density Lipoprotein and HDL is High-Density Lipoprotein. Neither LDL nor HDL is cholesterol, they are merely the carriers of cholesterol.
There are also other lipoproteins: VLDL (very low density lipoprotein), IDL (Intermediate density lipoprotein), and there is even an HDL2 and HDL3, not to mention chylomicrons. And when your doctor measures your cholesterol level, he is not making a definitive measurement but a guess, albeit a well-informed one.
The functions of the two lipoproteins is that LDL carries cholesterol from the liver out around the body to where it is needed for cell repair and all the other jobs that cholesterol does; and, as the body abhors waste and is a great recycler, HDL carries 'second-hand' cholesterol from cells being replaced back to the liver for re-use.
Neither HDL nor LDL is 'bad'; both are essential.