With as much information available about the trans fat content of foods and the generally accepted fact that trans fats are unhealthy, a short primer on the science behind trans fats can be helpful in understanding exactly what trans fats are.

Fats are molecules that contain a water-soluble region, the so-called “head” of the molecule, and water-insoluble “tails,” made up of carbon chains of varying lengths. The types of fats in the foods we eat, which are called triglycerides, have three “tails” attached to one “head.”

The carbon chains that make up the “tails” of fats can be classified into two general types, saturated and unsaturated, based upon the numbers of carbons and hydrogens. Saturated fats contain carbon chains with only single bonds between carbons and hydrogens. The carbon atoms are said to be “saturated” with hydrogens. Saturated fats stack together tightly, somewhat like the way that Lego blocks snap together. Because of the tight stack, saturated fats have a high boiling point and are, therefore, solid at room temperature. Examples of foods that contain a high proportion of saturated fats are shortening (baking grease) and meat.

Unsaturated fats contain double bond(s) between carbon atoms and, as a consequence, have less hydrogens than the corresponding saturated fats. Monounsaturated fats contain only one double bond, while polyunsaturated fats, which are more common, contain multiple double bonds.

Unsaturated fats can be further classified into two types, those with cis double bonds and those with trans double bonds. The terms cis and trans refer to the positions of hydrogen atoms in the double bonds in the carbon chains. If the hydrogens are on the same side of the double bond, the term cis is used, while if the hydrogens are on opposite sides, the term is trans. A cis-unsaturated fat has a “kink” in the carbon chain at the location of the double bond and, as a result, these types of fats do not stack together as efficiently as saturated fats.

Cis-unsaturated fats are usually liquid at room temperature such as vegetable oils, such as olive oil and nuts. A type of cis-unsaturated fats, called “omega-3 fatty acids,” contains double bonds in certain positions of their carbon chains. These fats are also called “good fats” because they have been found to be essential for child development. One such omega-3 fatty acid is DHA (docosahexanoic acid) is commonly added to infant formula and prenatal vitamins. Omega-3 fatty acids have also been found to be possibly beneficial in reducing heart disease and increasing circulation.

Trans-unsaturated fats are not naturally occurring except in ruminant animals. These types of fats are produced by the partial hydrogenation of cis-unsaturated fats. Since cis-unsaturated fats have a higher melting point than saturated fats, they also tend to become rancid faster. By adding hydrogen to cis-unsaturated fats (a process called hydrogenation) and decreasing the number of double bonds present in the carbon chains, the melting point of the fats can be increased. Since not all of the double bonds are hydrogenated, these fats are only partially hydrogenated. A side effect of this process is that some of the cis double bonds are converted into the more stable trans double bonds and not to the single bonds found in saturated fats.

Trans fats are attractive to those who produce snack foods because they are more liquid at room temperature than saturated fats but can still perform the same function of more solid fats in the baking process. Also, the use of relatively-inexpensive trans fats increases the shelf life of food products without the use of more expensive semi-liquid fats.

A current topic in the news has been the detrimental effects of trans fats on the health of those who consume them. This is partially due to the fact that trans fats, like saturated fats, are more solid than cis-unsaturated fats at body temperature and, therefore, there are semi-solid fats in our bodies.

Trans fats are also thought to be more resistant to breakdown by naturally occurring enzymes, called lipases, which leads to trans fats staying in our bodies for longer periods of time than their cis counterparts.

There is evidence that the consumption of trans fats can contribute to the development of heart disease and other diseases, including diabetes and cancer, although the evidence is not as strong.

The recognition that trans fats are detrimental to our health has led to a regulation mandating the listing of the trans fat content of foods in the United States. Foods that contain less than 0.5g of trans fat per serving are allowed to include the listing of 0g trans fat on their labels.

However, consuming multiple servings of such foods could still lead to the consumption of a significant amount of trans fats. Therefore, care must be taken when eating products that contain “partially hydrogenated oils.”

Weedsport native Lauren O'Neil holds a Ph.D. in organic chemistry from the University of Notre Dame. She will tackle current trends in her new monthly column by explaining the science behind such matters.