Trans fats are touted almost daily as bad for your cholesterol and overall health. However, what exactly are trans fats? And why are trans fats bad for your health?
Fats are a subclass of lipids (which also include waxes, steroids, and oils) called triglycerides and are composed of two sets of molecules: a glycerol and three fatty acids. Glycerol is a three carbon containing molecule that acts as the “skeleton” that holds the three fatty acids. The fatty acids themselves are composed of long carbon-to-carbon chains that have either single bonds, double bonds, or multiple double bonds residing between the carbons. When a fatty acid has all single bonds, it is called saturated, because every carbon atom is bound to either another carbon atom, a hydrogen, or some other atom. A fatty acid that has a single double bond between its carbons is called monounsaturated, while a fatty acid that has more than one double bond between its carbons is called polyunsaturated.
Examples of fatty acids include arachidonic acid (i.e., omega-6), a 20-carbon polyunsaturated fatty acid, as well as oleic acid, an 18-carbon monounsaturated fatty acid. Such fats are metabolized by enzymes such as cyclooxygenase and lipoxygenase into potent mediators including prostaglandins, leukotrienes, thromboxanes, and lipoxins. These mediators are essential to life.
Because many fatty acids are unsaturated or polyunsaturated, they are also liquid. This occurs because carbon atoms that are not fully saturated with other atoms often form kinks within the carbon-to-carbon chain. As such, fatty acids are unable to pack tightly and form solid masses at room temperature. In order to make this happen artificially, unsaturated fats are often subjected to a process called hydrogenation. Once hygrogenated, the oleic acid mentioned earlier becomes stearic acid and turns into a solid saturated fat. This occurs because hydrogenation of a fatty acid straightens out its “kinks”, making the carbon chain more compact and thus more likely to organize into a crystalline structure and solidify.
Synthetic saturated fats are useful for a number of reasons. First of all, they are inexpensive when compared to natural solid fats such as coconut oil or even lard. For this reason, hydrogenated fats are often added to inexpensive pastries, spreads, and even candies. Second of all, hydrogenated fats are less likely to break down and become rancid, a condition that plagues natural fat-containing items such as butter and lard. Because of this issue, hydrogenated fats are often added to foodstuffs, allowing those items to be kept fresh for months or even years at a time.
Unfortunately, what recent research has found out is that hydrogenated fats also have a propensity to form trans fatty acids during the process of hydrogenation. Trans fats occur when a fatty acid is being filled out by hydrogen atoms that migrate to opposite sides (i.e., trans) of two adjoining carbons rather than the same side (i.e., cis) of those carbons. Natural fatty acids typically have their hydrogen atoms placed in a cis configuration relative to groups of two adjoining carbon atoms.
Why should cis versus trans molecular configurations make any difference when it comes to your health? A cis fatty acid contains a larger “pocket” by which the aforementioned enzymes such as cyclooxygenase can enter and act upon the molecule. A trans fatty acid has a smaller “pocket” and, as a result, too much steric hindrance to allow for enzymatic activity. This renders the fatty acid incapable of being properly metabolized by the body (1). Most often, such fatty acids end up being excreted by the body, but they may also become stuck in certain places along the way, such as the arteries.
If trans fatty acids are incorporated into cellular membranes, their compact and dense structure often leads the cell to become brittle and damaged. Damaged cells can also become stuck in various regions of the body, although most often they end up attracting immune cells and giving rise to inflammation. Inflammation, of course, destroys neighboring cells and produces blood and tissue clots. Inflammation has been marked as one of the leading causes of cardiovascular disease.
As a result of such findings, trans fats are being slowly banned in foods and food additives. However, hydrogenation is not the only process by which trans fats are created. Monounsaturated and polyunsaturated fats (e.g., canola oil) are often used for cooking and deep-frying of foods. Unlike saturated fats such as lard, unsaturated fats are more labile and prone to structure change due to heat. As a result, cooking food in “healthy” oils such as canola or vegetable oil can result in the food becoming laden with trans fat. Due to this issue, many individuals who are trying to preserve their cardiovascular health actually prefer to fry and cook with “bad” fats such as butter or lard. For further information about this phenomenon, click on my own story of how I lowered my cholesterol almost 70 points by actually eating lard, butter, and other “bad” fats.
It does not take a large amount of trans fat to alter your total cholesterol, HDL, and LDL levels. In a study performed by Dr. Mensink, he and his colleagues found that even a 1% increase in dietary trans fats correlated with significant increases in total cholesterol, lower HDL, and higher LDL profiles for individuals who ate diets specifically prepared with different percentages of trans fat (2).
Because trans fats are being deemed increasingly bad for cardiovascular and overall health, the USDA has revised its dietary recommendations for individuals to include less trans fat and more natural and unsaturated fat (3). Food manufacturers are also being forced to update their ingredients listings to include amounts of trans fat; however, because many foods contain less than 1% trans fat (thus not obligating food manufacturers to report that ingredient), accurate reporting is not always performed.
References:
1. Niu SL, Mitchell DC, Litman BJ., Trans fatty acid derived phospholipids show increased membrane cholesterol and reduced receptor activation as compared to their cis analogs. Biochemistry. 2005 Mar 22;44(11):4458-65. PMID: 15766276
2. Martijti B Katan, Peter L Zock, and Ronald P Mensink, Effects of fats and fatty acids on blood lipids in humans: an overview, Am J Cli. Nutr., 1994;60(suppl):lOl7S-22S.
3. USDA Nutrition and Your Health: Dietary Guidelines for Americans. 2005 Dietary Guidelines Advisory Committee Report, Part D: Science Base, Section 4: Fats.
