h to each other and to hydrogen atoms. The term saturation refers to whether or not a fatty acid chain is filled (or “saturated”) to capacity with hydrogen atoms. If each available carbon bond holds a hydrogen atom we call this a saturated fatty acid chain. All carbon atoms in such a fatty acid chain are bonded with single bonds. Sometimes the chain has a place where hydrogen atoms are missing. This is referred to as the point of unsaturation.
When one or more bonds between carbon atoms are a double bond (C=C), that fatty acid is called an unsaturated fatty acid, as it has one or more points of unsaturation. Any fatty acid that has only one double bond is a monounsaturated fatty acid, an example of which is olive oil (75 percent of its fat is monounsaturated). Monounsaturated fats help regulate blood cholesterol levels, thereby reducing the risk of heart disease and stroke. A polyunsaturated fatty acid is a fatty acid with two or more double bonds or two or more points of unsaturation. Soybean oil contains high amounts of polyunsaturated fatty acids. Both monounsaturated fats and polyunsaturated fats provide nutrition that is essential for normal cell development and healthy skin.
3 chemical structures are shown. 1. Stearic acid or C subscript 18 H subscript 36 O subscript 2: a saturated fat. 2. Oleic acid or C subscript 18 H subscript 34 O subscript 2: a monounsaturated fat with a double bond. 3. Linoleic acid or C subscript 18 H subscript 32 O subscript 2: a polyunsaturated fat with 2 double bonds. Foods that have a high percentage of saturated fatty acids tend to be solid at room temperature. Examples of these are the fats found in chocolate (stearic acid, an eighteen-carbon saturated fatty acid is a primary component) and meat. Foods rich in unsaturated fatty acids, such as olive oil (oleic acid, an eighteen-carbon unsaturated fatty acid, is a major component) tend to be liquid at room temperature. Flaxseed oil is rich in alpha-linolenic acid, which is an unsaturated fatty acid and becomes a thin liquid at room temperature.
Knowing the connection between chain length, degree of saturation and the state of the fatty acid (solid or liquid) is important for making food choices. If you decide to redirect your intake of fat products, choosing unsaturated fat is more beneficial than choosing a saturated fat. Examples of foods high or rich in unsaturated fats include avocados, olive and canola oils(monounsaturated), most vegetable and fish oils (polyunsaturated), nuts and seeds. Conversely, tropical oils are an exception to this rule in that they are high in saturated fat. Palm oil and coconut oil are both highly saturated and have been shown to raise blood cholesterol. Shortening, margarine, and commercially prepared products (in general) report to use only vegetable-derived fats in their processing. But even so, some of these contain fats that may be in the saturated and trans fat categories.
Cis or Trans Fatty Acids?
The introduction of a carbon double bond in a carbon chain, as in an unsaturated fatty acid, can result in different structures for the same fatty acid composition. When the hydrogen atoms are bonded to the same side of the carbon chain, it is called a cis fatty acid. Because the hydrogen atoms are on the same side, the carbon chain has a bent structure. Naturally occurring fatty acids usually have a cis configuration.
In a trans fatty acid, the hydrogen atoms are attached on opposite sides of the carbon chain. Unlike cis fatty acids, most trans fatty acids are not found naturally in foods but are a result of a process called hydrogenation. Hydrogenation is the process of adding hydrogen to the carbon double bonds, thus making the fatty acid saturated (or less unsaturated, in the case of partial hydrogenation). This is how vegetable oils are converted into semisolid fats for use in the manufacturing process.
According to the ongoing Harvard Nurses Health Study, trans fatty acids have been associated with increased risk for coronary heart disease because of the way they negatively impact blood cholesterol lev