When you read articles about fats, authors are usually referring to triglycerides. When you eat something fatty like ice cream or a steak, you are consuming countless triglyceride molecules. Each triglyceride molecule (image on the left) is composed of three fatty acids bound together to a glycerol molecule. There are many in a drop of fat. When experts talk about unsaturated, polyunsaturated and saturated fats, they are referring to the proportion of fatty acids that compose the fat molecule (triglyceride).
From a chemical point of view, just know that there might be such a thing as a carbon to carbon double bond within the structure of a fatty acid. The number of double bonds allow scientists to classify fatty acids in different categories: saturated (no double bonds), or unsaturated (one or more double bonds). The unsaturated fatty acids are divided in two kinds: monounsaturated which have only a double bond and polyunsaturated which contain two or more double bonds.
Now, the fatty acids in each triglyceride (fat) molecule may be the same kind or they may be different. When nutritionists label coconut oil or lard as saturated fat, they mean there is an abundance of saturated fatty acids within that kind of fat. When they label olive oil as a monounsaturated fat they mean that it contains a high percentage of monounsaturated fats. They NEVER mean that that is the only kind of fat contained in those products.
This is what you need to know:
- There are three fatty acids in a triglyceride (fat) molecule.
- All three fatty acids within fat are not necessarily the same kind.
- There are many fat molecules in fatty food (oils, meats, dressings, butter, etc).
- The percentage of saturated, monounsaturated or polyunsaturatedfatty acids in the fat molecules (triglycerides) in food determine how nutritionists classify a particular food item.
Finally, you ingest fat in when you eat, but you also manufacture fats in your body. Fat in the body is also packaged as triglycerides. The same concept applies: three fatty acids and a molecule of glycerol makes up a fat molecule. The body can manufacture fats from proteins (meats, poultry) and from carbohydrates (sugar, corn syrup, potatoes, rice). Basically, eating too much food will always turn into fat (triglycerides) mostly stored in the liver, adipose cells (visible body fat) and muscle. When people get a lipid profile at the doctor to find out their triglycerides, they are mainly finding out the amount of fat in their blood. Too much fat (triglycerides) in the blood is detrimental to your health. But that is a subject for another blog entry.
Up next: What are saturated fats and unsaturated fats and where are omega 3 fatty acids found in food.