Polyunsaturated fat
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In nutrition, polyunsaturated fats are a fatty acid in which more than one double bond exists within the representative molecule. That is, the molecule has two or more points on its structure capable of supporting hydrogen atoms not currently part of the structure. By contrast, polyunsaturated fatty acids can assume a cis or trans conformation depending on the geometry of the double bond.
The lack of the extra hydrogen atoms on the molecule's surface typically reduces the strength of the compound's intermolecular forces, thus causing the melting point of the compound to be significantly lower. This property can be observed by comparing predominately unsaturated vegetable oils, which remain liquid even at relatively low temperatures, to much more saturated fats such as butter or lard which are mainly solid at room temperature. Trans fats are more similar to saturated fat than are cis fats in many respects, including the fact that they solidify at a lower temperature.
A fatty acid has a carboxylic acid at one end and a methyl group at the other end. Carbon atoms in a fatty acid are identified by Greek letters on the basis of their distance from the carboxylic acid. The carbon atom closest to the carboxylic acid is the alpha carbon, the next adjacent carbon is the beta carbon, etc. In a long-chain fatty acid the carbon atom in the methyl group is called the omega carbon because omega is the last letter of the Greek alphabet.
Omega-3 fatty acids have a double bond three carbons away from the methyl carbon, whereas omega-6 fatty acids have a double bond six carbons away from the methyl carbon. The illustration below shows the omega-6 fatty acid, linoleic acid.
Omega-3 fatty acids in fish oil, fish and seafood lowers the total amount of fat in your blood, which can lower your blood pressure and decrease the risk of getting cardiovascular diseases.[citation needed] Omega-6 fatty acids in sunflower oil and safflower oil also reduce the risk of cardiovascular disease, but can contribute to allergies and inflammation. [citation needed]
Polyunsaturated fat, along with monounsaturated fat are "healthy fats," the amount of which in one's daily diet should be near 45 g (in a 2000 calorie-per-day diet).[citation needed] Polyunsaturated fat can be found mostly in grain products, fish and sea food (herring, salmon, mackerel, halibut), soybeans, mayonnaise, soft margarine and fish oil. Polyunsaturated fat is necessary for the body and protects against illness.
[edit] Molecular description: Illustration of linoleic acid
