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Cholesterol

Cholesterol is an essential substance that is used to make up part of the cells in your body.  It can be used to make hormones that help regulate the metabolism and development of your body.  It helps the cells in your body keep their shape.   It can also be made into a detergent-like substance called bile acid that can help with digestion. 

All animals make cholesterol but plants don't.   If your body didn't make any cholesterol you wouldn't be alive since its necessary for normal development and metabolism.   The problem with cholesterol, however, is that it can't move around in blood by itself.  Technically its a lipid, like vegetable oil or lard.  It has to be shuttled around the body on very, very small particles made mainly of fat (or lipid) and protein.  That's where the word lipoprotein comes from (lipid+protein).

Cholesterol is transported through blood to different parts of the body on lipoproteins called VLDL and LDL.  Since cholesterol can't be broken down by the body any extra has to be removed and taken to the gut where it can be gotten rid of.  This clean up job is done by HDL. 

It's quite a balancing act with VLDL and LDL delivering cholesterol to different parts of the body and HDL cleaning it up.   Problems arise when there's too much VLDL or LDL doing the delivering or not enough HDL to clean it all up. 

Triglyceride

Triglycerides are one of the two main forms of energy in the body, the other being glucose (a sugar).  Triglyceride in the diet takes the form of animal fat and vegetable oils.  When we eat these they need to get from our stomach to different places in the body.  Like cholesterol, triglyceride is a lipid and so it doesn't dissolve in blood.  Instead it gets transported around blood, which is mostly water, on lipoprotein particles, mainly VLDL.

    As VLDL travels around the body the triglcyeride is delivered to those places that need it and any excess is taken back to the liver.  Some people with low levels of some proteins that hand out the triglyceride have a hard time gettnig rid of triglyceride and VLDL from their blood.  The VLDL stay in the blood longer and can get damaged so they need to be removed by white blood cells instead of the liver.  If this continues, particularly in the presence of high LDL, this can lead over several years to a heart attack or stroke.

  There is a lipoprotein, called a chylomicron, that is made in your gut.  It carries all the triglyceride and cholesterol that you eat.  It functions in much the same way as VLDL, delivering dietary triglyceride around the body.  Chylomicrons can also build up in the blood of some people and increase their risk of a heart attack.

Cholesterol fact:

A lot of cholesterol that gets taken to your gut for removal is actually reabsorbed into your bloodstream.  Some plant fiber (like oat bran) can attract cholesterol in your gut and prevent it from being reabsorbed into your bloodstream.