Trans Fatty Acids by Hollie Strawn

By at January 19, 2012 | 1:08 pm | Print

Trans Fatty Acids by Hollie Strawn

Trans fatty acids are an industrially produced fat originally meant to replace saturated fats in processed foods and in commercial and household cooking and frying. (Harvard School of Public Health 2012) Numerous studies have shown the harmful effects of this product produced from once healthy unsaturated vegetable oil. (Benatar 2010) The differences between saturated and unsaturated fatty acids and how the hydrogenation process produces the trans configuration along with a brief history of trans fatty acids will follow and may help educate consumers. (Stein 1996)

Saturated, mono-unsaturated and poly-unsaturated all describe fatty acids and reference the number, if any, of double bonds between the carbon atoms in comparison to the number of hydrogens attached to the hydrocarbon tail. When a fat contains all single bonds between the carbons in the fatty acid tails, the carbons are bonded to the highest number of hydrogens available. These fatty acids are called saturated as they hold the maximum number of hydrogens. The straight shape of the saturated fatty acid hydrocarbon chain allows them to bundle tightly together and makes this fat solid at room temperature. Animal sources are the main provider of saturated fatty acids in the diet. (Stein 1996)

Oils originating from plant sources have varying numbers of double bonds between the carbons in the hydrocarbon tail, unlike saturated fats with all single bonds. These double bonds create a bend in the shape. The carbons sharing the double bonds are then not bonded to the maximum amount of hydrogens, and are called unsaturated fatty acids. Those unsaturated fats with only one double bond are named mono-unsaturated fats, and those with two or more double bonds are named poly-unsaturated fats. The aforementioned bends in the shape of the hydrocarbon tails due to the double bonds prevents them from bundling as tightly together as the straight saturated fats, making them liquid at room temperature. (Stein 1996)

The segments of the hydrocarbon tail of the unsaturated fatty acids can be arranged in the cis or trans configuration around the C=C double bond. The cis bond has the segments of the carbon chain on each side of the double bond arranged so that both are on the same side of the molecule. They could reside on the upper or lower section, but both will be situated together in either place. (Stein 1996) In comparison, trans bonds arrange both segments of the molecule around the C=C double bond on opposite sides of each other. As opposed to being situated on the same side as in the cis configuration, trans switch them across from one another. The partial hydrogenation of the vegetable oil generates the trans configuration, as does repeatedly frying with the same used oil. (Stein 1996)

There are only two sources of trans fatty acids in the human diet. The first is found in dairy and meat products from ruminant animals. Bacteria residing in the gut or digestive system of animals such as cows and deer hydrogenate fatty acids from the foods they eat which produce a trivial amount of trans fatty acids. Up until the widespread use of trans fats in processed foods, this was the main source of any trans fat found in the human diet. The most prevalent isomer of trans fatty acid found in milk is vaccenic acid, Trans 18:1n7. Ruminant trans fatty acids have not shown to be as harmful as industrial types in studies; however the reason for this is not fully understood. (Benatar 2010) (Harvard School of Public Health 2012) The other source of trans fatty acids in our diet is manufactured, or industrially processed, trans fatty acids made by partially hydrogenating vegetable oils. The most prevalent isomer of trans fat found in processed food is elaidic acid, Trans 18:1n9. (Benatar 2010)

The history of the production of industrially processed trans fat begins around 1902, and starts with the patent for the process of hydrogenating liquid oil being granted to scientist Wilhelm Normann. It was discovered that adding hydrogen atoms to the liquid vegetable oil, an unsaturated fat, by inserting hydrogen gas along with a nickel catalyst caused the liquid to become a solid. Furthermore, this new solid can tolerate reheating without degrading, and Crisco vegetable shortening became the first product to contain the new trans fat and was available statewide in approximately 1911. The trans fat solid product was easy to use and cheaper than animal lard or tallow. This lower expense for food manufacturers combined with butter rationing during World War II framed the rise in popularity of margarine with consumers. (American Heart Association 2010) The eventual reputation saturated fat gained for increasing cholesterol, among other negative consequences, motivated fast food companies such as McDonalds and Dunkin Donuts to replace beef tallow with partially hydrogenated vegetable oil for frying foods. (Harvard School of Public Health 2012) (American Heart Association 2010)

Another attractive quality of partially hydrogenated oils for food manufacturers was that it helped processed foods stay fresh longer, giving them a longer shelf life, as well as a less greasy feel. Over the last several decades, partially hydrogenated oils became a main ingredient in margarines, commercial baked goods, and snack foods of all kinds with the resulting intake increasing dramatically. (Harvard School of Public Health 2012) (American Heart Association 2010)

However, unknowingly and to the detriment of our health, during the partial hydrogenation process, the essential qualities of the molecule are changed as well as the shape. These fatty acids are merged into the cell, and research conducted in the 1990’s begins to show the harmful and dangerous effects this creates. Inflammation increases, and adverse effects are seen in lipids while the flexibility and pliancy of the cell wall and the integrity and functionality of the vascular endothelium are disrupted. (Benatar 2010) (Lopez-Garcia et al. 2005)

Meta-analysis of these studies as well as recent studies present steady and unambiguous results linking increased trans fat dietary intake with reduced high-density lipoprotein (HDL) and increased low-density lipoprotein (LDL) and triglyceride levels. Additionally, increased lipoprotein(a) and L DL-C particle size reduction are seen with the increased trans fat intake. While both are contributing factors in cardiovascular heart disease, the increased inflammation and the decreased functioning of the vascular endothelium arising from a diet high in trans fatty acids combine to raise the risk of heart disease. (Benatar 2010)

One study highlighting inflammation as a negative effect of trans fat consumption is especially seen in a study conducted on over 700 nurses. The quintile group with the highest consumption had C-reactive protein levels in their blood that were fully seventy-three percent higher than the quintile group with the lowest trans fat consumption. (Lopez-Garcia et al. 2005)

To demonstrate detrimental effects on cardiovascular health due to increased trans fatty acid intake, the Nurse’s Health Study, or NHS, results are highlighted. Over 120,000 female nurses with over 20 years of follow-up and nearly 900 chronicled heart related incidents were analyzed. A relatively small increase of just two percent, roughly equivalent to a teaspoon, was linked to an over twenty-five percent increase in cardiovascular disease risk. Cardiovascular heart disease risk nearly doubled for each two percent increase of trans fatty acid intake from processed foods as well. In comparison, for saturated fat to gain this considerable of an increased risk, at least fifteen percent of total daily energy would need to be consumed. (Benatar 2010) (Lopez-Garcia et al. 2005)

With multiple studies consistently showing the harmful effects of trans fats, food manufacturers are decreasing usage of partially hydrogenated products. Food labels were required to list trans fats along with saturated and unsaturated fats as of January 1, 2006. The Harvard School of Public Health, among others, advocated this change to food labels and countered the protests from some in the food industry. They additionally helped to educate consumers about the dangers of trans fats present in a vast majority of processed foods. Nearly one hundred percent of crackers and nearly eighty percent in of breakfast products such as waffles contained trans fats at that time. Now many products are being produced trans-fat free in response to consumer demand. (Harvard School of Public Health 2012) It is important however to remember that the FDA allows products to be labeled trans fat-free if a single serving contains half a gram or less. Depending on the number of serving you may ingest, or the frequency of consumption, checking the ingredient list for “partially hydrogenated vegetable oil” or “shortening” and replacing the product with another one without these ingredients could be a wiser and ultimately healthier alternative. (Harvard School of Public Health 2012) (American Heart Association 2010)

As more food manufacturers are responding to consumer demands for healthier alternatives to industrially processed trans fatty acids, consumption and the resulting harmful effects could be lowered. (American Heart Association 2010)

The American Heart Association. 2010. A history of trans fat. [Online] Available: January 12, 2012 Benatar, Jocelyn. 2010. Trans fatty acids and coronary artery disease. Dovepress Journal: Open Access Journal of Clinical Trials [Online] Available January 10, 2012 Carter, J. Stein. 1996. Lipids: Oils, fats, waxes, etc. [Online] Available January 12, 2012 Lopez-Garcia, Esther, Schulze, Matthias B., Meigs, James B., Manson, JoAnn E., Rifai, Nader, Stampfer, Meir J., Willett, Walter C., Hu, Frank B. 2005. Consumption of trans fatty acids is related to plasma biomarkers of inflammation and endothelial dysfunction. The American Society for Nutritional Sciences Journal of Nutrition. 135:562-566 Harvard School of Public Health. 2012. The Nutrition Source. Shining the spotlight on trans fats. [Online] Available January 13, 2012

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