Unsaturated fat
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
| Types of Fats in Food |
|---|
|
| See Also |
An unsaturated fat is a fat or fatty acid in which there are one or more double bonds in the fatty acid chain. A fat molecule is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond. Where double bonds are formed, hydrogen atoms are eliminated. Thus, a saturated fat is "saturated" with hydrogen atoms. In cellular metabolism hydrogen-carbon bonds are broken down - or oxidized - to produce energy, thus an unsaturated fat molecule contains somewhat less energy (i.e fewer calories) than a comparable sized saturated fat. The greater the degree of unsaturation in a fatty acid (ie, the more double bonds in the fatty acid), the more vulnerable it is to lipid peroxidation (rancidity). Antioxidants can protect unsaturated fat from lipid peroxidation. Unsaturated fats also have a more enlarged shape than saturated fats.
Chemistry and Nutrition
Double bonds may be in either a cis or trans isomer, depending on the geometry of the double bond. In the cis conformation hydrogens are on the same side of the double bond, whereas in the trans conformation they are on opposite sides (see also Trans fat). Saturated fats are popular with manufacturers of processed foods because they are less vulnerable to rancidity and are generally more solid at room temperature than unsaturated fats. Unsaturated chains have a lower melting point, hence increasing fluidity of the cell membranes.
Both mono- and polyunsaturated fats can replace saturated fat in the diet; trans unsaturated fats should be avoided. Substituting (replacing) saturated fats with unsaturated fats helps to lower levels of total cholesterol and LDL cholesterol in the blood. Trans unsaturated fats are particularly bad because the double bond stereochemistry allows the fat molecules to assume a linear conformation which leads to efficient packing (i.e., plaque formation). The geometry of the cis double bond introduces a bend in the molecule precluding stable formations (see specific fatty acid links above for drawings that illustrate this). Natural sources of fatty acids (see above) are rich in the cis isomer.
Although polyunsaturated fats are protective against cardiac arrhythmias a study of post-menopauseal women with a relatively low fat intake showed that polyunsaturated fat was positively associated with progression of coronary atherosclerosis, whereas monounsaturated fat was not [1]. This probably is an indication of the greater vulnerability of polyunsaturated fats to lipid peroxidation, against which Vitamin E has been shown to be protective [1].
Examples of unsaturated fats are palmitoleic acid, oleic acid, linoleic acid, and arachidonic acid. Foods containing unsaturated fats include avocado, nuts, and vegetable oils such as soybean, canola, and olive oils. Meat products contain both saturated and unsaturated fats.
Although unsaturated fats are healthier than saturated fats,[1] the old Food and Drug Administration (FDA) recommendation stated that the amount of unsaturated fat consumed should not exceed 30% of one's daily caloric intake (or 67 grams given a 2000 calorie diet). The new dietary guidelines have eliminated this recommendation. Most food contain both unsaturated and saturated fats. Marketers only advertise one or the other, depending on which makes up the majority. Thus, various unsaturated fat vegetable oils, such as olive oils, also contain saturated fat.
Insulin resistance correlates positively with monounsaturated fat (especially oleic acid) and negatively with polyunsaturated fat (especially arachidonic acid) in the phospholipids of human skeletal muscle [1].
Membrane composition as a metabolic pacemaker
Cell membranes of mammals have a higher composition of polyunsaturated fat (DHA, omega-3 fatty acid) and a lower composition of monounsaturated fat than do reptiles. Higher polyunsaturated membrane content gives greater membrane fluidity (and functionality), commensurate with the higher metabolic rate of the warm-blooded species. In fish, however, increasingly cold environments lead to increasingly high cell membrane content of both monounsaturated and polyunsaturated fatty acids, presumably to maintain greater membrane fluidity (and functionality) at the lower temperatures[1]
References
See also
- Saturated fat
- Monounsaturated fat
- Polyunsaturated fat
- Trans fat
- Iodine number - a chemical analysis method to determine the proportion of unsaturated fat.
External links
fr:Acide gras insaturéko:불포화 지방산 ja:不飽和脂肪酸 no:Umettet fettsimple:Unsaturated fat
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
