The liver is the primary organ that makes cholesterol. The liver also packages cholesterol so it can travel easily through the bloodstream to different parts of the body, manages blood cholesterol levels, and breaks cholesterol down and repackages it for excretion from the body. Certain medical conditions can affect the liver's ability to properly control blood cholesterol levels.
Significance
The liver is responsible for manufacturing cholesterol in all animals, which is why beef liver, calves liver, chicken liver and other animal livers eaten by humans are very high in cholesterol. This organ not only produces its own cholesterol, it processes all cholesterol that comes into the body through the diet.
Types
While there is one type of cholesterol, there are several types of lipoproteins that contain cholesterol and carry it throughout the body. The two most commonly known lipoproteins are high-density lipoprotein (HDL), which is often referred to as the "healthy" cholesterol and low-density lipoprotein (LDL), which is often referred to as the "bad" cholesterol. Other important types of cholesterol-carrying lipoproteins packaged by the liver include very low-density lipoprotein (VLDL) and chylomicrons. The difference is in the amount of fat and protein contained within each type of lipoprotein. The lower density lipoproteins contain a higher ratio of fat to protein.
Function
The liver typically produces about 700 mg to 900 mg of cholesterol a day, according to Iowa State University Extension Service. This is as much as the body needs for the variety of functions cholesterol serves, including the production of vitamin D, hormones and bile acids used to digest fat. The liver packages LDLs to carry cholesterol from the liver to cells in every other part of the body. HDLs carry cholesterol from cells back to the liver where it is repackaged for removal from the body.
Effects
When cholesterol is consumed in food, the liver produces less so the body can maintain a normal level of blood cholesterol. This balancing mechanism doesn't work the same way for everyone, however, and some people must control their blood cholesterol levels through diet and, sometimes, with the help medication. If the liver produces too much cholesterol, the excess LDL may stick to artery walls as it travels through the bloodstream. Eventually this causes a build-up that narrows the open passageways of the arteries and restricts the flow of blood. The result is atherosclerosis, or clogged arteries, that can lead to a heart attack.
Considerations
Some people have a genetic disorder, known as familial hyperlipidemia, which prevents their livers from managing cholesterol production and blood levels. A diet high in saturated fats and trans fatty acids can raise blood cholesterol levels in people with and without familiar hyperlipdemia. Those with the condition may also need to take cholesterol-lowering medication to keep their blood levels in a normal range. Other medical conditions, such as diabetes and liver disease, can cause excessively high or low blood cholesterol levels.
