What are the Different types of Cholesterol?
What is Cholesterol?
Cholesterol is technically known as lipids or fats. It resembles a waxy powder that looks like candle wax shavings. It is light yellow in color. All animals need cholesterol to survive. Lipids provide chemical energy as fuel for the cells that make up our body. And it is responsible for the protective shell or membrane for cells. It is also essential for digestion and absorption of nutrients from food.
Cholesterol is essential for our sex hormones, testosterone and estrogen, and for vitamin D. Cholesterol is so important that our body regulates it so closely that if you did not consume enough dietary cholesterol, your body would produce all it needs on its own. Your liver has the ability to convert fats, sugars and proteins into cholesterol for its needs.
Different types of Lipoproteins.
Your bloodstream is the vehicle which delivers cholesterol and other lipids to every cell in the body. Since lipids and blood don’t easily mix well, the body knows to wrap protein around cholesterol particles making it easy to flow within the bloodstream. This is where the term lipoprotein gets its name. Your bloodstream carries many different sizes of lipoproteins which are categorized based on the density or fat composition. More fat equals lower density. Less fat and more protein means higher density. There are actually 4 different fat containing particles in the blood. HDL or high density lipoproteins have the least amount of fat (and triglycerides) and the most protein. The largest and least dense is something called chylomicrons which contain the most fat; specifically triglycerides. The other 2 are LDL or low density lipoproteins and VLDL or very low density lipoproteins. Most of the fat from our diet and the non-cholesterol fat in our bloodstream is triglycerides. Triglycerides are made up of three fatty acids and glycerol, an alcohol. Triglycerides are essential for our health and provide much of the energy our tissues need, but too much of a good thing, like cholesterol, can be dangerous to your circulatory health.
Triglycerides, Chylomicrons and VLDL
After food passes from the stomach to the intestines fat is absorbed from the food. Intestinal enzymes dismantle the long fat molecules into fatty acids and combine them with cholesterol into chylomicrons. The intestines release a large amount of chylomicrons filled with triglycerides into the blood. Triglyceride levels remain very high hours after eating. This is why Doctors order fasting cholesterol tests. Otherwise triglyceride levels would show up in the lipid panel as being abnormally high. While this process is occurring, dietary carbohydrates and proteins pass from the intestines to the liver. They are converted to triglycerides and combined with cholesterol and protein creating VLDL particles which are released into the blood. As VLDL and chylomicrons travel through the bloodstream, they temporarily stick to the artery walls providing energy. Enzymes remove most of the triglycerides and what remains is rearranged and relabeled to be used again by the liver.
How LDL is created
As triglycerides are removed from VLDL and chylomicrons, they become smaller and denser. Ultimately all that remains is the protein and cholesterol and a minute amount of triglyceride. The liver filters out the chylomicron and recycles any remnants unlike VLDL which even after it has lost its triglyceride components, continues to circulate. VLDL continues to change and ultimately ends up as LDL particles. LDL carries the majority of our cholesterol. Practically all cells in the body can utilize LDL for their energy needs. However there is typically more LDL in the bloodstream than is needed and the liver must clear the excess from the blood. It may use it for more bile acids for digestion or as new lipoproteins. If the liver cannot keep up with the excess LDL, it ends up being deposited in places it does not belong. Often this excess LDL ends up being deposited in the blood vessel linings. Occasionally these deposits end up in the skin or tendons where they may form xanthomas or xanthelasmas if they are formed on the eyelids. They appear yellow in color.
HDL, the Savior
High density lipoproteins are known as the “good” cholesterol and for valid reasons. HDL is also made in the liver and intestines but is very different than LDL. There is a high concentration of protein and not much fat in HDL. The two primary roles of HDL are to provide chylomicrons and VLD the protein component that allows the liver to recognize they need to have their fat extracted. HDLs also act as scavengers and collect excess cholesterol from blood vessel linings and other locations to be transported to the liver to be disposed of. Recently there have been studies suggesting that HDL may even counteract inflammatory molecules in LDLs which is known to cause scarring to blood vessel walls. This scarring encourages plaque and calcium to build up in the damaged areas leading to atherosclerosis. HDL obviously plays a vital role in maintaining a healthy cholesterol balance.