Biochemistry Of Fatty Acids

Biochemistry of Fatty Acids WHAT IS FATTY ACID? Fatty Acids, common name for a group of organic acids that includes the saturated (hydrogenated), straight-chain acids, with a single carboxyl (COOH) group, that are produced by the hydrolysis of fats. The group also includes all other saturated straight-chain acids and acids with a branched chain or cyclic structure. Methanoic (formic) acid, HCOOH, and ethanoic (acetic) acid, CH3COOH, are the simplest fatty acids1. Both have a sour taste, irritate the skin, and have a sharp smell. Of more complicated structure are butanoic, hexanoic and octanoic acids, all of which have unpleasant odours. Stearic, palmitic, oleic, and naphthenic acids are greasy materials with little odour. A growing source of fatty acids is tall oil, a byproduct of the pinewood used to make paper pulp. Fatty acids are useful in preparing biodegradable detergents, thickeners for paints, and lubricants. Stearic acid is used to combine rubber with other substances, such as pigments, or materials that control the flexibility of rubber products; it is also used in the polymerization of phenylethene (styrene) and butadiene in making artificial rubber. New uses for fatty acids include ore flotation and the manufacture of disinfectants, varnish driers, and heat stabilizers for vinyl resins. Fatty acids are also used in plastic products, such as coatings for wood and metal, and in car parts ranging from air-cleaner housings to upholstery. FATTY ACIDS IN OILS AND FATS2

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Biochemistry of Fatty Acids TYPES Fatty acids can be saturated3 and unsaturated, depending on double bonds. In addition, they also differ in length. Only unsaturated fatty acid will be discussed in-depth here. UNSATURATED FATTY ACID In unsaturated fatty acids, there are two ways the pieces of the hydrocarbon tail can be arranged around a C=C double bond. In cis bonds, the two pieces of the carbon chain on either side of the double bond are either both “up” or both “down,” such that both are on the same side of the molecule. In trans bonds, the two pieces of the molecule are on opposite sides of the double bond, that is, one “up” and one “down” across from each other. Naturally-occurring unsaturated vegetable oils have almost all cis bonds, but using oil for frying causes some of the cis bonds to convert to trans bonds. If oil is used only once like when fry an egg, only a few of the bonds do this so it’s not too bad. However, if oil is constantly reused, like in fast food French fry machines, more and more of the cis bonds are changed to trans until significant numbers of fatty acids with trans bonds build up. The reason this is of concern is that fatty acids with trans bonds are carcinogenic, or cancercausing4. The levels of trans fatty acids in highly-processed, lipid-containing products such as margarine are quite high.

Saturated fatty acids have a chain of carbon atoms joined by single bonds, allowing for rotation about the bonds. 4 Trans-fatty acids do not have the beneficial effects of cis-fatty acids such as glycemic control, energy balance etc. It is therefore recommended (by Danish Nutrition Council) that intakes of trans-fatty acids should not rise above the current average of about 2 per cent of energy intake. 3

Biochemistry of Fatty Acids MORE ABOUT TRANS FAT Most trans fats are created artificially by a process called hydrogenation. It involves heating regular vegetable oil and forcing hydrogen atoms onto the polyunsaturated fatty acid molecules. This process turns the oil into a solid substance and improves the shelf life of the fat. Fully hydrogenating a vegetable oil will make it firm and not create trans fats. However, the firmness of the fat makes it difficult to use in cooking. Partially hydrogenating an oil makes for a softer product and is still widely used in baking and processing foods. Examples include stick margarine and partially hydrogenated frying oils. Trans fats are commonly found in donuts, snack cakes, cookies and processed foods. Artificially created trans fats are the unhealthiest of fats, even worse than saturated fat 5. Eating too many trans fats has been linked to increasing your risk of cardiovascular disease. Not all trans fats are created in the lab. Small amounts of natural trans fats occur in milk and beef. Conjugated linoleic acid is a well-known natural trans fat. The natural trans fats do not appear to be as unhealthy as the artificial trans fats. FOODS CONTRIBUTE TO TRANS FATTY ACID INTAKE6 Milk and cheese Butter Eggs Meat and meat product Oil and fats Biscuits and cakes Savoury pies, etc Chips, French fries Others TOTAL

18.8 5.9 0.9 10.3 35.5 16.5 3.5 4.5 4.1 100

Natural Natural Natural Natural Mainly resulting from hydrogenation Mainly resulting from hydrogenation Mainly resulting from hydrogenation Mainly resulting from hydrogenation Mainly resulting from hydrogenation

TRANS FAT AND HEART Recent studies have suggested that trans fatty acids (TFA) have a deleterious effect on cholesterol levels and the risk of heart disease. Ingestion of TFA is implicated in coronary heart disease (CHD) are based on changes induced in plasma cholesterol levels. Within the range of intakes of 3-11 % of dietary energy there is a dose-response relationship; an increase of 1 % of the total energy intake (at the expense of oleic acid) increased low density lipoproteins (LDL) by 0.04 mmol/l and decreased high density lipoproteins (HDL) by 0.013 mmol/l. This amounts to a 1 % reduction in HDL and a 1 % increase in LDL. TFA increase LDL to the same extent saturated fatty acid (SFA), but reduce the beneficial HDL. In short, trans fatty acids turn out to increase total cholesterol levels and LDL cholesterol levels, and to reduce HDL cholesterol levels.

Saturated fats are almost always found in foods that also contain cholesterol, so saturated fats offer a "one-two" punch to heart health. On the other hand, trans fatty acids not only increase LDL cholesterol, they also decrease HDL cholesterol 6 Information statement (2007) from Institute of Food Science and Technology Trust Fund, UK 5

Biochemistry of Fatty Acids OTHER NEGATIVE EFFECT OF TRANS FATTY ACID 1. Essential fatty acids (EFA)7 are transformed in the body by a series of reactions into long chain polyunsaturated fatty acids essential for development of the nervous system and eyesight. TFA compete with EFA for the enzyme systems involved in these reactions. High intakes of TFA have been shown to influence the metabolism of EFA in experimental animals when the EFA intake was low. Frank deficiency in EFA is only found in abnormal circumstances in human adults. However, new-born infants, and especially if premature, show borderline deficiency in EFA, and their TFA intake from the mothers milk is related to her TFA intake. 2. There is conflicting evidence concerning the possible role of TFA in breast cancer. As part of the EURAMIC (European Community Multicentre Study on Antioxidants, Myocardial Infarction, and Breast Cancer) study, Kohlmeier et al (1997)8 investigated the relationship between TFA and postmenopausal breast cancer in European populations differing greatly in their dietary fat intakes. A case control study using adipose tissue stores of TFA as a biomarker of exposure was conducted. Subjects included 698 postmenopausal incident cases of primary breast cancer and controls randomly drawn from local population and patient registries, ages 50-74. Concentrations of individual TFA in gluteal fat biopsies were measured in these women. The adipose concentration of TFA showed a positive association with breast cancer, not attributable to differences in age, body mass index, exogenous hormone use, or socio-economic status. The authors conclude that these findings suggest an association of adipose stores of TFA with postmenopausal breast cancer in European women, but point out that they require confirmation in other populations, with concomitant consideration of the potential roles of dietary saturated and monounsaturated fats. 3. Obesity: Research indicates that trans fat may increase weight gain and abdominal fat, despite a similar caloric intake. A 6-year experiment revealed that monkeys fed a transfat diet gained 7.2% of their body weight, as compared to 1.8% for monkeys on a monounsaturated fat diet. Although obesity is frequently linked to trans fat in the popular media, this is generally in the context of eating too many calories; there is no scientific consensus connecting trans fat and obesity. 4. Liver Dysfunction: Trans fats are metabolized differently by the liver than other fats and interfere with delta 6 desaturase. Delta 6 desaturase is an enzyme involved in converting essential fatty acids to arachidonic acid and prostaglandins, both of which are important to the functioning of cells. 5. Infertility: One 2007 study found, "Each 2% increase in the intake of energy from trans unsaturated fats, as opposed to that from carbohydrates, was associated with a 73% greater risk of ovulatory infertility…” TRANS FATTY ACID IN PALM AND PALM KERNEL OIL PRODUCT Malaysia produced around 50% of world’s palm and palm kernel oil product last year. According to Journal of Oil Palm Research Vol. 14 No. 1, June 2002; trans-fatty acids were generally absent in crude palm and palm kernel oils. However, they were present at 0.01%0.06% in refined palm kernel products and 0%-0.61% in refined palm products, all well below the 1.0% level stipulated by some importers such as United Kingdom and United States. These trans-fatty acids were formed from their natural cis-isomers as a result of the high temperature used during deodorization. In cooking oil, the trans-fatty acid contents of palmbased products were 0.25%-0.67%, again well below 1%. However, in the non-palm-based Some of the example are Omega-6 and Omega-3 Published in journal from Institute of Nutrition, Friedrich Schiller University Jena, Dornburger Street 25-29, 07743, Jena, Germany (2003) and American Journal of Clinical Nutrition, Vol 42, 1201-1205, The American Society for Clinical Nutrition, Inc. 7 8

Biochemistry of Fatty Acids cooking oils, the contents ranged from 0.43%-3.83%. The higher contents in the non-palmbased oils were expected as they had high contents of unsaturated fatty acids, which are more prone to isomerisation at elevated temperatures. In the nutshell, this provides us with further evidence that palm and palm kernel oil products are excellent9 hard-stocks for trans-free formulation of texturized fatty products such as margarines, shortenings, confectionery fats, and vanaspati (a hydrogenated vegetable oil commonly used in South Asian cooking instead of butter). These products can advantageously replace hydrogenated fats which contain not only trans-fatty acids, but also possibly a host of other unnatural and polymerized fatty acids formed during hydrogenation to reduce their unsaturation.

Center of Science of Public Interest, USA, made up a controversy and false statement that "Consumers and food processors should realize, though, that palm oil still promotes heart disease and that producing palm oil has a devastating impact on rainforest and endangered wildlife". CSPI executive director Michael F. Jacobson also said "We applaud food manufacturers for moving away from trans-fat-laden partially hydrogenated oils, and happily, many companies are switching to such heart-healthy oils as soybean, corn, or canola" 9