Webster's Dictionary defines a trans-fatty acid as follows:
*Main Entry: trans-fat·ty acid
*Pronunciation: 'tran(t)s-'fa-tE-, 'tranz-
an unsaturated fatty acid characterized by a trans arrangement of alkyl chains that is formed especially during the hydrogenation of vegetable oils and has been linked to an increase in blood cholesterol
Unsaturated vegetable oils from canola, peanuts, olive, flax, corn, safflower and sunflower that have not been hydrogenated are considered Essential Fatty Acids (EFAs). They contain essential vitamins and minerals needed to maintain a healthly lifestyle. Several of these components are rich in antioxidants. Unprotected EFAs have a short life span, and the last thing the oil manufacturers want is for us to buy their oil in the grocery store, just to find that it has gone bad. To avoid this, they remove and chemically change them and we (consumers) foot the bill. By the time the oils we eat have been refined, a radical change has taken place.
After heating normally "safe" saturdated fats and vegetable oils, the molecules have rearranged themselves. The diagram on the right shows a EFA molecule before hydrogentation. Hydrogen molecules have jumped around and twisted from being heated, stiffening and hardening the substance. This creates a thick build-up over time in important arteries and blood vessels.