Principles of nutrition – Part 3
Fats: Chemical composition of fats
Fats in the body, otherwise known, as triglycerides are compounds formed by three long chain fatty acids and an alcohol, glycerol. Glycerol is a triol, which has three active hydroxyl (-OH) groups, which will react with three long chain fatty acids to form triglycerides. Fats are generally hydrophobic; they are insoluble in water but soluble in certain other solvents. The shorter chain fatty acids are liquid at room temperature while those with longer chains are solid. Because of these different qualities, it is common to refer to those that are liquid at room temperature as oils and the solid ones at room temperature as fat. However, they are all lipids.
Good and bad oils (fats) and their health implications
We shall be looking at fats in a little more details than we considered the first two macronutrients – carbohydrates and proteins. Some reasons why we are looking at fats more deeply would include the different types, the health benefits of them and their uses. Fats in the body are commonly referred as fatty acids. Fatty acids are so called because of their involvement in the biochemical processes that occur in the body. They are carboxylic (dominated by carbon atoms) acids with long chains. This long chain is either saturated or unsaturated. The saturated chains have all the carbon atoms linked to hydrogen atoms. The unsaturated ones have some carbon atoms that are linked to hydrogen atoms while the rest are free. Ordinarily, the hydrogenated carbon atoms would confer a not too good status to such an acid, but they do have some beneficial effects in the body. As a result of this, the unsaturated fatty acids are the good and healthy ones while the saturated fatty acids are the bad and unhealthy fatty acids. Fatty acids are derivatives of triglycerides and phospholipids and they are said to be free fatty acids when they are not attached to any other molecule.
Of major interest to us are the Essential Fatty Acids. They are referred to as essential because they are utilized in the body as fuel for generation of energy, ATP, but they are not synthesized in the body. They must be gotten from the food that we eat. Fatty acids that are of use in the body can be classified as saturated and unsaturated fatty acids, The unsaturated fatty acids, can be further divided into mono-unsaturated fatty acids and poly-unsaturated fatty acids, depending on the number of carbon atoms that are linked to hydrogen atoms.
Polyunsaturated Fatty Acids
These are fluid and free-flowing oils that remain liquid whether at room temperature, in the body or inside the refrigerator. They keep the cell membranes fluid and flexible. They participate in the functions of the glands and organs. The bad effects of the saturated fatty acids can be neutralized when the concentration of the polyunsaturated fatty acids outnumber that of the saturated ones. Omega 3 fatty acids lower both the bad LDL-cholesterol and triglyceride levels in the blood.
Good sources of omega 3 fatty acid are canola, flaxseed and walnut. There is also a high concentration of omega 3 in fish oil. Omega 3 and omega 6 are two important nutrients that the body needs. They are both found in nuts and seeds and their oils. The richest source of omega 3 is flaxseed. Omega 3 in seed oil is in the form of alpha-linolenic acid (ALA), which can be converted in the body to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are forms in which omega 3 can be used in the body and in fish oils they already exist as EPA and DHA.
Monounsaturated Fatty Acids
These fatty acids remain liquid at room and body temperatures. Monounsaturated fatty acids lower cholesterol and prevent plaque formation on the walls of the arteries. They reduce the risk of hypertension and heart disease. Olives, canola and peanut oil are important sources of monounsaturated fatty acid. Other beneficial properties of olive oil are its support of the heart muscles to pump blood more efficiently and prevention of heart disease. Also of note, are the anti-cancer properties of olives.
Saturated Fatty Acids (Bad fats).
These are found in animal meat and everyday diet of carbohydrates and proteins. Saturated fatty acids that remain solid either in room temperature or in the body are primarily used for energy production and insulation. They are potentially harmful. For example, they have the tendency to stick together to form clots, which can lead to coronary heart disease or stroke. Excessive consumption of saturated fatty acids increases the risk of cardiovascular disease.
Hydrogenated and Trans-Fatty Acids.
As I mentioned earlier, unsaturated fatty acids have some carbon atoms that are not linked with hydrogen. An unsaturated fatty acid becomes saturated or hydrogenated when hydrogen is pumped into it at very high temperatures. This process converts the liquid unsaturated fatty acid to a solid form of fatty acid. Hydrogenated fatty acids become toxic and stick together easily, to form plaques and increase the blood pressure.
Examples of hydrogenated and trans-fatty acids are margarine from vegetable oils, solid shortening from partially hydrogenated vegetable oils, lard (pig fat), butter etc.
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