A lipid is the name for a type of compound that contains the elements carbon, oxygen and hydrogen. Lipids are hydrophobic, which means they do not dissolve in water. The lipids in the body play an important role in insulation, storage of energy, cell structure and protein transportation, according to “Nutrition and You,” by Joan Salge Blake. There are three major forms of lipids: sterols, phospholipids and triglycerides.
Sterols, which are made up of four rings of carbon and hydrogen, act as precursors to a variety of different substances in your body. The most well-known sterol is cholesterol. Cholesterol makes up part of the membranes of your cells and acts as a precursor for vitamin D and bile acids, which are needed to properly digest fats that you consume in your diet. Cholesterol is also a precursor for the sex hormones estrogen and testosterone. The right amount of cholesterol in blood is essential for proper body function. When cholesterol levels get too high, however, they can increase your risk of developing heart disease. “Nutrition and You” notes that it is not necessary to consume any dietary cholesterol because all of the cholesterol you need for normal body function is synthesized in your body.
Phospholipids are composed of three fatty acids and a phosphorous group. Fatty acids are made up of a chain of carbon and hydrogen atoms and contain an acid group at the end of their structure. More than 20 different types of fatty acids exist. The phosphorous portion of the phospholipid is polar, which means it attracts charged particles. The fatty acid portion of the phospholipid is nonpolar, and it does not attract any particles. The phospholipids in your body are arranged together in what is referred to as the phospholipid bilayer. This layer surrounds your cells and acts as a protective barrier, allowing water into the cell but keeping important elements from being excreted from the cell. “Nutrition and You” notes that lecithin is the major phospholipid contained in your cell membranes.
Triglycerides are the chemical form fat takes in your blood. Triglycerides can be consumed through your diet or synthesized in your body from excess calories or carbohydrates, according to the American Heart Association. When you consume excess calories, they are stored as triglycerides in your fat cells. The body uses these triglycerides as a source of energy between meals or during times of fasting. If you consume excess calories on a regular basis, triglycerides remain in your bloodstream instead of becoming stored in your fat cells. Excess levels of triglycerides in your bloodstream can lead to the development of atherosclerosis and coronary artery disease.
- Nutrition and You; Joan Salge Blake; 2008
- American Diabetes Association: All About Cholesterol
- American Heart Association: Triglycerides