Fats - Triglycerides, Phospholipids and Sterols
Fats, also known as lipids, are divided up into three groups:
Ninety-five percent of the fat in food are triglycerides, and 99% of the fat stored in the body are triglycerides. Fats/lipids provide energy and insulates the body. Lipids made up of carbon, hydrogen and oxygen atoms. Most lipids are insoluble in water.
Triglycerides are made of a glycerol molecule with three fatty acids attached to it. The length of the fatty acids and how much they are saturated varies from one fatty acid to another. Without going into detail, when no more hydrogen atoms can be added to the fatty acid, it is called 'saturated'. Those that do not have the maximum amount of hydrogen are called either monounsaturated or polyunsaturated. The amount of saturation has an effect on how it is utilized by the body.
Phospholipids represent less then 5% of the lipids in the food we eat. Phospholipids are soluble in both fat and water. Because of this they can move across cell membranes. Lecithin is the most famous phospholipid. Lecithin is found in peanuts, liver, eggs, wheat germ and soybean, but is also made by the liver.
Like phospholipids, sterols are less than 5% of the lipids in food. Well known sterols include cholesterol, testosterone, cortisol and vitamin D.
Digestion of Lipids
Lipid digestion starts in the mouth with the enzyme lipase. Then in the stomach the lipids get broke down just a little bit more by a gastric lipid. Most of the digestion of fat takes place in the small intestine by other lipase enzymes such as pancreatic and intestinal lipases.
Essential Fatty Acids
There are only two fatty acids that the body needs that it can't make itself. These are linoleic acid and linolenic acid. Linoleic acid is sometimes referred to as omega-6 fatty acid and linolenic acid as omega-3 fatty acid. Since the body cannot make these, we need to get them from food we eat. Seeds, nuts and fish are high in these fatty acids.