Trans fats have been so vilified that nutritional labels list how many grams of trans fats food contains. Whatever did they do to earn criminal status in the macronutrient world?
Chemistry students should recognize that “trans” refers to how the fatty acid chains are shaped; trans fats are zig-zagged. The terms “cis” and “trans” are applied to some bonds within fatty acid chains to differentiate the chains that curve like a U and those that curve like a Z. Most unsaturated fats that health-companies tout in their products are cis fats. In terms of physical properties, trans fatty acids and cis fatty acids are only marginally different; trans fats experience higher melting points since they’re more symmetrical but also lower boiling points. They show up a little differently on chemical analyses (e.g. exhibit different splitting in proton NMR).
Trans fats are unsaturated fatty acid chains, so they should pose less of a health concern than saturated fat. In terms of biology, it’s not entirely clear why trans fats are supposed to be bad. We know they are–scientific research indicates that trans fat consumption increases serum low-density lipoprotein (LDL) and decreases high-density lipoprotein (HDL) concentrations. Throwing off this ratio increases risk of heart and cardiovascular diseases.
Turns out, there may be more to the story than just trans vs cis. Studies in Canada funded by Alberta Livestock and Meat Agency and Dairy Farmers of Canada have shown that the trans fats naturally found in beef and dairy are actually beneficial to health. Specifically, vaccenic acid lowers total cholesterol levels while decreases LDL and triglyceride in the blood. However, due to the relative scarcity of such studies, public awareness towards trans fats has yet to be altered.
A growing number of nutritionists and biologists propose that the problem isn’t trans fat; instead, health problems are the result of the chemical manufactured unsaturated fat. The chemical hydrogenation process used in industry often is incomplete and produces trans fats (in contrast enzymatic conversion produces cis fats). Some hypothesize that the partial hydrogenation of unsaturated fatty acids to trans fats constructs trans fats detrimental to health, though naturally produced trans fats do not have the same negative effects.