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Learn more about "Polyunsaturated"

Polyunsaturated fat

In nutrition, '''polyunsaturated fat''' is an abbreviation of polyunsaturated fatty acid. That is 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. Polyunsaturated fatty acids can assume a ''cis'' or ''trans'' Conformational isomerism|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 fat|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 alphabet|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.

Health

Benefits

Polyunsaturated fat can be found mostly in grain products, fish and sea food (herring, salmon, mackerel, halibut), soybeans, and fish oil. Foods like mayonnaise and soft margarine may also be good sources, but nutritional facts can vary by style and brand. Omega-3 fatty acids in fish oil, fish and seafood have been shown to lower the risk of Myocardial infarction|heart attacks. Omega-6 fatty acids in sunflower oil and safflower oil also reduce the risk of cardiovascular disease, but can contribute to allergy|allergies and inflammation. Omega-3 fatty acids '''reduced prostate tumor''' growth, slowed histopathological progression, and increased survival. ''Among n-3 fatty acids Omega-3, neither long-chain nor short-chain forms were consistently associated with breast cancer risk. High levels of docosahexaenoic acid, however, the most abundant n-3 PUFA Omega-3 in erythrocyte membranes, were associated with a '''reduced risk of breast cancer'''.''.

Relation to cancer

Some studies have shown that consuming high amounts of polyunsaturated fat may increase the risk of an individual developing cancer. This is thought to be because polyunsaturated fat is prone to oxidation, which leads to the generation of Radical (chemistry) | free radicals and eventually to rancidification|rancidity. Studies have shown that low dosages of Coenzyme Q10 reduce this oxidation, and a combination of a diet rich in polyunsaturated fatty acids and Coenzyme Q10 supplementation leads to a longer lifespan in rats. Studies on animals have shown a link between polyunsaturated fat and the incidence of tumours. In some of these studies the incidence of tumours increased with increasing intake of polyunsaturated fat, up to about 5% of total energy, near to the middle of the current dietary intake in humans. However, studies in humans have found little evidence of an association between polyunsaturated fat and the risk of cancer. It is advised that the level of polyunsaturated fats in the diet be regulated if Coenzyme Q10 supplements are not being taken. However, even without Coenzyme Q10 supplementation, the effect on health might be more beneficial than harmful in terms of its effect on reducing cholesterol levels. A high consumption of omega-6 '''polyunsaturated fatty acids''' (PUFAs), which are found in most types of vegetable oil, may increase the likelihood that postmenopausal women will develop '''breast cancer'''. Similar effect was observed on '''prostate cancer'''. Other ''analysis suggested an inverse association between total polyunsaturated fatty acids and breast cancer risk, but individual polyunsaturated fatty acids behaved differently'' from each other.

Some Examples of Foods containing polyunsaturated fat

- fish
- cereal
- whole grain wheat
- peanut butter
- margarine
- bananas (however, at .33 grams fat per serving, this food is considered "fat-free" by FDA standards)
- sunflower seeds
- hemp seed

References

External links

- The Chemistry of Unsaturated Fats Category:Fatty acids Category:Nutrition Category:Lipids simple:Polyunsaturated fat

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Sources: StartLearningNow, Wikipedia | Usage license: GNU FDL

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