Breakin ’ it Down! Trans Fatty Acid Style

1. Breakin’ it Down! Trans Fatty Acid Style Rebecca Curry, Laura Hardy, Kaitlin Glynn, Megan Solloway Figure 1. Cis double bond Figure 2. Trans double bond Trans Fats in the Body The increased bond strength in trans fatty acids compared to saturated fatty acids causes similar, and yet more detrimental effects in the body. Decreased Nutrient Uptake: TFAs make cell membranes more rigid and less fluid. Rigidity of a cell membrane desensitizes membrane Receptors, therefore preventing nutrients from entering the cells. Susceptibility to Oxidative Stress: Altered fatty acid composition of membranes increases the cell’s susceptibility to oxidative stress. Increased Inflammation: TFAs accumulate in cell triacylglycerolsand phospholipids. As triacylglycerols accumulate, liver, muscle, and pancreatic cells respond by activating inflammatory pathways. Insulin Resistance: Lipid-activated inflammatory pathways inhibit insulin signaling, therefore reducing insulin-stimulated glucose consumption in skeletal muscles. Change in Intestinal Flora: A high fat diet alters the ratio of gram-negative to gram-positive bacteria in the intestinal flora, resulting in a significant increase in fat mass, body weight gain , liver triglyceride accumulation, insulin resistance, and diabetes. High amounts of TFAs may also alter gut microbiota composition, which is associated with obesity and hepatic steatosis. What are Trans Fats? Trans fatty acids (TFAs) are artificially created by forcing hydrogen atoms into the double bonds of polyunsaturated fats to produce a fatty acid with similar properties to saturated fats. This process, called hydrogenation, forces hydrogen atoms into a trans orientation across the fatty acid double bond (Figure 2). Now, one hydrogen is oriented above the double bond and one hydrogen is below. This trans orientation prevents the polyunsaturated fatty acid from kinking and forces the fatty acid into a linear orientation. A linear alignment allows TFAs to pack together tightly, increasing the melting point. A higher melting point indicates the presence of strong bonds in the molecule. Trans Fats and Cardiovascular Disease Trans fat and cardiovascular disease (CVD) seem to have become synonymous in recent years. The link can be made based on the fact that Trans fats have been studied and shown to increase the levels of low density cholesterol, LDL, in our systems but having little or no impact on the beneficial high density cholesterol, HDL. Clinical trails conducing a meta-analysis looked at Trans fats’ effects on blood lipid levels and found a strong correlation between trans fats and elevated serum LDL cholesterol. The study results also revealed that out of all the fatty acids tested, trans fats were the only ones that did not raise HDL. Low amounts of HDL present hinders HDL’s action of sweeping cholesterol out of the body. High amounts of LDL and low amounts of HDL in the blood stream increases the ratio of total cholesterol to HDL cholesterol, which is a strong risk factor for CVD. The clinical trials also suggested that trans fats might be linked to CVD due to their increasing effect on blood triacylglycerol concentrations, association with systemic inflammation and their possibly damaging effects to endothelial cells within the veins and arteries of the body. A staggering statistic obtained from a prospective study stated that a trans fat intake of 2% of total energy correlated to a 23% increase in the risk of CVD. A separate community-based prospective cohort also supported the fact that trans fats are linked to cardiovascular disease after analyzing blood plasma levels. This study was even able to go further and connect trans fats as the greatest of all the fatty acids as a predictor for all-cause death. This study also found a correlation between LDL particle size and trans fatty acid consumption. Trans fatty acids were found to decrease the size of LDL particles; this is a negative component of their ingestion because smaller LDL particles can more easily clump in damaged endothelial cells of the arteries and cause plaque build up. If there are enough small LDL particles around this build up can form into a blockage or break off and cause a myocardial infarction among other detrimental effects. Figure 3. Fatty acids and membrane fluidity • Where are Trans Fats Found? • Man-made Trans fats create a desirable taste and mouthfeel and are found most often in fried foods and baked goods. Look out for them in fast food and other prepared foods such as doughnuts, pot pies, soup cups, and pizzas. Baked goods and their dry mixes such as muffins, cakes, and other pastries are more of the most likely foods to contain TFAs. Other snack foods such as crackers, chips candy, and even microwave popcorn have been known to incorporate TFAs too along with popular toppings like gravy, salad dressings, and whipped toppings. Margarine, vegetable shortening, and butter are the underlying culprits for many of these foods. “Tub” versions contain less TFAs per serving than the stick versions. Nutrition Facts labels are only required to include trans fats if the product contains over 0.5 g per serving, but a product contains TFAs if “hydrogenated” or “partially hydrogenated” oils are on the label. How Are Trans Fats Digested in the Body? Bans and Restrictions The divisive choice was made in 2006 to ban the use of artificial trans fats in all New York City restaurants. It was initially met by a slight uproar from angry restaurant owners displeased with having to change their menus. However the policy allowed for a transition time declaring that all trans fats had to be eliminated by 2008; allotting time for new recipes and cooking techniques to be implemented in increments. Others displeased by the ban felt that it was going too far by trying to ‘legislate diets’. Loopholes were able to be found within the policy; such as permitting restaurants to serve foods containing trans fats as long as they had come that way from the manufacturer and were not further manipulated by the restaurant. New York City was the first to take this health action, but since the bill’s passing, other cities have followed suit and begun to regulate the use of trans fats as well. Are All Trans Fats “Bad”? Current research suggests that not ALL trans fats are unhealthy! In animals such as cows, sheep, and goats, there are certain gastrointestinal bacteria that naturally hydrogenate the fatty oils from animal feed . This naturally occurring TFA is termed Conjugated Linoleic Acid (CLA) which can be found in beef and lamb products and full-fat dairy products. While it isvery clear that industrial and naturally-occurring TFAs have differenteffects than artificially made TFAs, it isn’t completely clear yet whether these natural TFAs actually have a beneficial effect. A promising study did show a decrease in total cholesterol, LDL, and triglyceride levels in healthy adults who consumed natural TFAs. It also showed that only industrial TFAs lower HDL levels. A possible anti-carcinogenic effect of natural TFAs has also been questioned. However, more research is definitely needed in this areato provide a definite answer. Trans fats are structurally different than other fats found in nature. Their structure is in the “trans” configuration instead of the “cis” configuration. This change of shape makes the trans fat a straight molecule. After the fatty acid is ingested, it reacts with pancreatic lipase in the stomach in order to create free fatty acids. The intestinal cells then make them into triacylglycerols and they are transferred as chlylomicrons into the liver. Once there they are made into either very-low density lipoproteins (VLDL) or low density lipoproteins (LDL)