Trans Fat: The Chemistry, the Health Risks and the Control

(Photo: http://www.putnamcountyny.com/livehealthyputnam/nutrition/transfat/transfatwhatis.png)



Polyunsaturated, saturated, monounsaturated, omega-3 Fatty Acids, trans fat, cholesterol. All of the above are types of fats that are regularly consumed yet most people don’t know why we are recommended to completely avoid some fats and eat others in moderation. Fats can be divided into two main types, saturated fat and unsaturated fat. Saturated fats have the maximum number of hydrogen atoms and therefore, don’t have any carbon-carbon double bonds. Unsaturated fats, on the other hand, have carbon-carbon double bonds because the molecule doesn’t have the maximum number of hydrogen atoms. The number of double bonds in a unsaturated fatty acid can be decreased through hydrogenation. Complete hydrogenation involves the addition of hydrogen atoms to all empty positions creating a saturated fat. Partial hydrogenation is also the addition of hydrogen atoms to an unsaturated fatty acid but all of the empty hydrogen positions are not filled so the fatty acid remains unsaturated. This process is typically completed commercially to increase shelf life by decreasing the number of double bonds. Unsaturated fatty acids are typically in the cis configuration (Hydrogen atoms on the same side of the carbons involved in a double bond). The partial hydrogenation of unsaturated fats, adds hydrogen atoms to the molecule to decrease the amount of double bonds, and consequently transforms the remaining double bonds of the unsaturated fatty acid to the trans configuration (Hydrogen bonds are on opposite sides of the double bond).(Photo Below: http://porpax.bio.miami.edu/~cmallery/150/chemistry/fig4x6b.jpg)
This slight configuration difference plays a big role in the structure of the molecules. The cis isomer is noticeably kinked while the trans isomer is straight, a similar structure to that of saturated fatty acids. (Photo Below: http://www.pleo.com/dupont/nomex/aramid07.gif) The trans isomer has a higher melting point because it can form a solid that is difficult to break apart because the straight structure allows it to pack more tightly than the kinked cis configuration. Partial hydrogenation is used commercially to make a fat that is solid at room temperature and melts when baked or eaten. But while the fatty acid becomes less prone to rancidity, it also increase risk of heart disease in the consumer.



Trans fats do occur naturally in the milk and meat of cattle (they are produced by bacteria in the rumen), but the primary source of consumed trans fat is commercially produced through partial hydrogenation. Naturally, only 4% of the total fat in the meat and milk of cattle is trans fat. Commercially, however, as much as 45% of the total fat is trans fat; 30% of total fat in shortening is trans fat (“Trans fat”, 2008). Trans fats are often found in vegetable oils and are commonly used in fast food chains, restaurants, bakeries, and snack foods. The semi-solid consistency of the partially hydrogenated fat allows bakers to replace lard and butter and therefore to produce kosher food. Partially hydrogenated oil is also much less expensive than other semi-solid oils. The question then is: Does the reduced price outweigh the health risks?
In the 2005 Dietary Reference, The National Academy of Science (NAS) claimed that “trans fatty acids are not essential and provide no known benefit to human health.” A separate study at the Harvard School of Public Health, came to a similar conclusion, “The consumption of trans fatty acids form partially hydrogenated oils provides no apparent nutritional benefit and has considerable potential for harm” (Mozaffarian, 2006). (Photo Above: http://www.abouttownguide.com/dutchess/articles/winter02/images/whats_wrong.jpg) The NAS further explained that “there is a positive linear trend between trans fatty acid intake and LDL cholesterol concentration, and therefore increased risk of CHD [Coronary Heart Disease].” More specifically, “any incremental increase in trans fatty acid intake increases CHD risk” (NAS, 2005). Trans fats contribute to an increased risk of CHD through their interaction with the lipase enzyme. The lipase enzyme is necessary for the absorption and digestion of lipids within the body because it functions to breakdown consumed lipids and allows for their absorption. The problem with trans fats, is that human lipase is specific to the cis configuration of fatty acids and is ineffective to trans fatty acids. Therefore, trans fatty acids cannot be broken down or absorbed and remain in the blood stream longer making the consumer more susceptible to arterial deposition and plaque formation, primary symptoms of CHD. Many studies have proven that there is a strong connection between the consumption of trans fat and the risk of CHD. According to a study completed at the Harvard School for Public Health by Mozaffarian et al, “the consumption of trans fatty acids raises levels of low-density lipoprotein (LDL) cholesterol, reduces levels of high-density lipoprotein (HDL) Cholesterol and increases the ratio of total cholesterol to HDL cholesterol, a powerful predictor of [increased] risk of CHD” (Mozaffarian et. al, 2006). Also, Mozaffarian et al suspect that the systemic inflammation caused by trans fat intake could correspond to as high as a 30% increased risk of heart disease. More specifically, their research concluded that a “2% increase in energy intake from trans fatty acids was associated with a 23% increase in the incidence of CHD” (Mozaffarian, 2006). According to the Center for Science in the Public Interest (CSPI), 50,000 fatal heart attacks are caused by trans fat consumption each year (“Trans fat”, 2006). It is suspected that trans fat consumption could also lead to an increased risk of the following chronic diseases: Alzheimer’s Disease, Cancer, Diabetes, Obesity, Liver dysfunction, and infertility, but studies involving these diseases and the consumption of trans fats haven’t produced sufficient data to confirm these suspicions.


Due to the extreme health risks associated with trans fat consumption, trans fat has been gradually banned across the world. In 2003, the debate over trans fats became public with the lawsuit against Oreo Cookies. Kraft was sued for marketing Oreo cookies that contained trans fats to children. This created a rapid increase in awareness of the health risk of trans fats across the world. Less than a month later, Mars Bars and Snickers in Britain became trans fat free and The White House requested that the “Health and Human Services (HHS) issue stronger warnings about the danger of trans fats” (bantransfats.com, 2007). Over the course of the next year many companies announced their plans to make their products trans fat free. In April 2004, Kraft foods introduced the new and improved trans fat free Oreo cookie. Only a few weeks later, Smucker announced a zero trans fat Crisco shortening. The new shortening is made with fully hydrogenated oils (a solid) blended with sunflower and soybean oil to soften it (bantransfats.com, 2007). In May 2004, the Center for Science in the Public Interest (CSPI) filed a petition, which was supported by many of the top scientists in the country, with the FDA to ban partially hydrogenated oils. (Photo Above: http://weblogs.baltimoresun.com/entertainment/dining/reviews/blog/%20Trans-Fat-free-Construction.jpg)In October 2004, Tiburon, CA became the first trans fat-free city in America and in November, Canada passed a motion to limit trans fat content in all food products. In 2005, the USDA and the HHS released dietary guidelines recommending that trans fatty acid consumption should be kept as low as possible. More specifically, the FDA recommended that daily intake of trans fat should be “less than 2 grams, perhaps less than 1 gram” (bantransfats.com, 2007). In December 2005, the three most popular Girl Scout Cookies, Thin Mints, Caramel deLites and Peanut Butter Patties became trans fat free. On January 1, 2006 the FDA required all packaged foods in the United States to list trans fat content on their Nutrition Facts labels. Under these regulations, however, if a serving contains less than 0.5 grams of trans fat, it can be expressed as zero (“Trans Fat”, 2008). This is a major problem because if you look carefully on the Nutrition Facts Label in the picture at the right (http://angelweave.mu.nu/images/CheetosBack1.jpg) it claims that each serving contains 0g trans fat but the ingredients contain “partially hydrogenated soybean oil”, which is known to contain trans fats. Therefore, it is very important to inspect the Nutrition labels of products that claim they are trans fat free. The trans fat ban progressed to fast food chains, restaurants, and even cities during 2006. In April 2007, The American Heart Association (ADA) launched The Bad Fat Brothers campaign to spread the word about the health risks of trans and saturated fat. (Photo Below: http://www.badfatsbrothers.com/BFB.html)

Today 20% of the US is has banned trans fat. This is expected to increase as the publics knowledge of the health risks of trans fat consumption expands. (Photo at right: Trans Fat Bans in Restaurants, http://www.cspinet.org/transfat/index.html).




References

National Academy of Science [NAS]. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) Online Summary. The National Academies Press; 2005. 423- 424, 427-428.



Center for Science in the Public Interest, About Trans Fat (http://www.cspinet.org/transfat/about.html)
Mozaffarian, “Trans Fatty Acids and Cardiovascular Disease”, The New England Journal of Medicine. Vol 354 No. 15, April 2006. (1602-1613).



“Trans Fat,” http://en.wikipedia.org/wiki/Trans_fat (2008)