You may already know all of the warnings that accompany high levels of cholesterol; that cholesterol is linked to heart disease and an unhealthy diet. But, what you may not know is what exactly cholesterol is, how it comes to be inside your body or the different types of cholesterol. Knowing the ins and outs of cholesterol can help you make good decisions about your lifestyle and the food that you eat.
Makeup
Cholesterols are made of lipids, a technical term for fat molecules. The lipid known as cholesterol, has many uses inside of your body including protecting your nervous system cells and cellular membranes. For this reason, cholesterol needs to be transported around the body. However, there is one problem, cholesterol is hydrophobic, meaning it doesn't mix well in your blood. Lipoproteins are small proteins that are assembled by your body to carry cholesterol molecules where they need to go. The cholesterol is safely stored inside of the protein so that it can move around your bloodstream freely. Lipoproteins also serve as a method of cellular recognition. In other words, cells respond to the presence of a lipoprotein when it draws near to it, aiding the transfer of cholesterol from the blood and into the cell.
Types of Lipoproteins
There are four major types of lipoproteins: chylomicrons, high-density lipoproteins, low-density lipoproteins and very low-density lipoproteins. Each type varies in size and function. Chylomicrons deliver cholesterol to storage sites of fat around your body. High-density lipoproteins move cholesterol from the bloodstream into the liver where it may be used for bile and excreted. Low-density lipoproteins carry cholesterol in the bloodstream and to the cells that need it. Very low-density lipoproteins also carry fat to storage sites, however, once the fatty acids have been deposited, their cholesterol forms a low-density lipoprotein, adding to the cholesterol in your blood.
Cells and Cholesterol
Your cells have the ability to make cholesterol. Your body works in balance, maintaining all of the nutrients it needs, including cholesterol. Your cells do not necessarily need dietary cholesterol, because they can make what they need. If cholesterol is running low, your cells signal the internal pathways to make cholesterol, even increasing the amount of cholesterol receptors around their membrane, in order to take more cholesterol in.
Liver and Cholesterol
Your liver cells make so much cholesterol, they produce enough to release cholesterol into the bloodstream. Much like your other cells, the liver can sense when cholesterol is running low. When your liver makes cholesterol, it is able to attach the cholesterol to a lipoprotein and release it into the bloodstream for use by your other cells. In addition, your liver may also use some of the cholesterol it makes as bile. Bile aids the digestion of fat in your diet.
References
- "Anatomy and Physiology"; Kenneth S. Saladin; 2004
- Harvard School of Public Health: Understanding Cholesterol: The Good, The Bad and The Necessary
- Gastroenterological Society of Australia; The Digestive System: Liver
