UNDERSTANDING THE BASICS OF FAT
Dietary fats are the source of fat-soluble vitamins A, D, E, and K and of Essential Fatty acids (EFAs). They are mainly triglycerides (combination of glycerol and three fatty acids), but also contain other types of fats. Sources in the diet in clued not only the visible fats (such as butter, margarine and vegetable oils) but also the so called invisible fats found in meat, fish, poultry and dairy products.
Dietary fats and first dissolved by the action of bile salts and then broken down into fatty acids and glycerol by lipase, a pancreatic enzyme. They are then absorbed by the lymphatic system before entering he bloodstream. The lipids are carried in the blood, bound by a protein thus becoming a lipoprotein. There are 4 classes of lipoproteins: Chylomicrons, Very Low Density (VLDL), Low Density (LDL) and High Density (HDL). LDLs and VLDLs contain large amounts of cholesterol, which they carry thru the bloodstream and deposit in cells. The HDLs pick up cholesterol and take it bake to the liver for processing and excretion.
Nutrients that provide the body with its most concentrated form of energy, 1 gram of fat provides 9 calories, where as 1 gram of carbohydrates provides 4-5 calories. Fats are compounds containing carbon and hydrogen with very little oxygen. Chemically, they consist mostly of fatty acids mixed with oily alcohol, glycerol. They are divided into two main groups, saturated and unsaturated, depending on the proportion of hydrogen atoms. If the fatty acid contains the maximum quantity of hydrogen, they are said to be saturated. If there are some sites on the carbon atom that are unoccupied by hydrogen they are unsaturated; when may sites are vacant they are polyunsaturated. Animal fats, such as those found in meat and dairy products are highly saturated with hydrogen, while vegetable fats tend to be unsaturated to varying degrees.
Also referred to as Lipids, include triglycerides, phospholipids and sterols. Triglycerides are the main form of fat found in stores of body fat. These stores act as an energy reserve as well as providing insulation and protective layering for delicate organs. Phospholipids are structural fats found in cell membranes. Sterols, such as cholesterol, are found in animal fat and plant tissue; they have a variety of functions in the body, often being converted by chemical action into hormones or vitamins.
Organic acids, containing carbon, hydrogen, and oxygen, that are constituents of fats. There are over 40 different fatty acids found in nature, distinguished by their number of carbon atoms. Certain fatty acids cannot be synthesized by the body and must be provided by the fat in the diet. These fatty acids are linolenic, linoleic and arachidonic acid, sometimes referred to collectively as the Essential Fatty Acids (EFAs).