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Jun
17
2011

The Skinny on Trans Fats

Fats are either solid or liquid at room temperature.  If liquid, we often refer to them as oils.  When discussing the differences between fats, it all boils down to organic chemistry (sorry!).  Fats are long molecules, made mostly of carbon atoms bonded together in a long chain, with specialized ends.

Fat MoleculesEach carbon atom has four potential places for things to bind.  Usually each carbon is represented to bond to one Carbon on each side (single bond), and to Hydrogen above and below.  In this case, each of the potential places for Hydrogen to bond is “saturated” with a Hydrogen atom.  If, however, Carbon forms two bonds (double bond) with another Carbon, only one additional place is left to bind with Hydrogen.  In this case, the fat is “unsaturated” with Hydrogen (not all potential spaces for Hydrogen to bond are filled with Hydrogen).  (Figure 1)

Cis Fats vs Trans Fats

Unsaturated fats have double bonds between Carbon atoms.  ‘Trans’ and ‘Cis’ refer to how the large parts of the chemical chain are arranged.  In trans fats, the large parts of the chemical chain are across from each other; in cis fats, the large parts are on the same side of the double bond. (Figure 2)

Hydrogentaion is the process of adding Hydrogen to cis-unsaturated fats in order to eliminate the double bonds between Carbon atoms, and make them saturated.  In partial hydrogenation, the double bonds are eliminated, but trans-unsaturated fats (trans fats) are formed.

No trans fats are essential in our diet. They increase LDL (bad cholesterol) in our blood while decreasing HDL (good cholesterol).  Trans fats increase our risk for heart disease, and serve no vital purpose.  We should limit trans fats as much as possible in our diet.

For most of human history, animal-based fats were the only source for trans fat in our diet.  Now, most trans fats are created from partial hydrogenation of plant fats (mostly vegetable oils).  Foods that contain the highest concentration of trans fats include fast foods, fried foods, snack foods (potato chips, crackers, etc.), nondairy creamer, and many baked goods. Partial hydrogenation of plant fats may produce up to 45% trans fat compared to the total fat in a particular food.  Baking shortenings, potato chips, stick margarine, and many candy bars, for example, contain about 30% trans fats; tub margarine has about 7%, and butter has about 4%.

So, why partially hydrogenate our food?  Partial hydrogenation increases product shelf life, and decreases refrigeration requirements.  Fast food companies believe that it “keeps food fresh.”  Furthermore, partial hydrogenation has financial incentive.  Trans fats have just the right consistency to replace animal fats such as butter and lard; and, trans fats are far less expensive.

There are, however, glimpses of hope… In July 2003, the FDA required trans fat to be listed on every Nutrition Facts panel.  (Interestingly, foods with less than 0.5 grams of trans fat per serving may be listed as having 0 trans fat on the food label.)  In 2005, New York began a public education campaign, and also began limiting the amount of trans fats served in restaurants. “Phase Out Artificial Trans Fat In New York City Food Service Establishments” is a brochure created as part of this city-wide campaign.

In 2004, J.M. Smucker Company, makers of Crisco, began using a healthier palm oil, mixed with soybean oil and sunflower oil. KFC, Wendy’s, and McDonalds have reduced trans fat in their menus, and Chick-fill-A has been trans fat free since 2007.

Last year, California began prohibiting restaurants from using artificial trans fats in oil, shortening, and margarine for spreads or frying (with the exception of deep frying doughnuts).  Tiberon, California, was the first to mandate that all restaurants cook with trans fat-free oils.