The World of Lipids
Part 1- What are Lipids?
Before you can see the ways in which lipids impact your health, it is important to have a basic working understanding of what lipids are in the first place. Well, lipids are simply fats, which are a type of organic molecule- meaning molecules generally made by living things. What makes lipids different from other organic molecules
such as proteins or carbohydrates, is that they do not readily dissolve in water. This is why olive oil will float on top of water, or why Italian salad dressing separates in the refrigerator. Because your blood behaves like water, your body needs to use a clever trick for moving lipids around the bloodstream. We will come back to this in a minute. While there are many different types of lipids in your body, there are 2 that are the primary focus for the purposes of metabolic health: cholesterol and triglycerides.
Cholesterol is used to provide structure to a cell. Every cell in your body has a shell around it called a membrane, and cholesterol is a critical component of the membrane. Having too much or too little cholesterol will drastically alter the function of the membrane, causing the cell to be injured or even die. Because it is absolutely vital, each cell has the ability to make its own cholesterol, and has tightly regulated ways of keeping the amount of cholesterol in the cell in the “Goldilocks” range. If there is too little cholesterol cells will just make more- too much cholesterol and the cells will unload it into the bloodstream. Cholesterol can also serve as a building block for
other things in our body such as some vitamins, hormones or bile. But mostly cholesterol is there for cell structure.
Triglycerides look very different from cholesterol, as you can see in the picture above. They serve a markedly different purpose as well. Triglycerides are used as a source of energy for the body to perform its day to day functions. The structure of triglycerides makes them perfectly suited to provide an extremely
efficient fuel for cells, similar to diesel fuel for trucks. Triglycerides get into the blood in 2 ways: they are either absorbed in the intestines from the food you eat, or manufactured in the liver. Once in the bloodstream triglycerides are delivered to cells to be burned for energy. When there are extra triglycerides beyond what cells are using they are stored as fat for later use. In a metabolically healthy person, the triglycerides are stored in fat cells under the skin, though when metabolic health breaks down fat can build up in other organs such as the liver- with significant
negative consequences. This is one of the hallmarks of “metabolic syndrome” which will be reviewed in part 2.
As I alluded to above, lipids don’t dissolve in water. As a result, animals have developed mechanisms to transport lipids through the bloodstream in little bubble-like particles called lipoproteins, this name coming from the fact that they contain both lipids and proteins. These particles shelter, or shield, the lipids from the water-like blood stream around them, allowing the lipids to be easily moved through the body. These lipoprotein particles act like a submarine motoring under the surface of the ocean, and deep in the belly of the sub is its cargo- cholesterol and triglycerides.
In part 2 we will take a look at the ways in which lipids, or more precisely the lipoprotein particles that carry the lipids, impact our health and our risk for chronic disease.