What are trans fatty acids?
Unsaturated fats, found in such foods as avocados and olive and
corn oils are heart healthy, but in the air they can go rancid
by absorbing oxygen and then decompose, C&EN explains.
Manufacturers can stop this process by bubbling hydrogen
(hydrogenation) through the fat at a high temperature in the
presence of a catalyst like nickel and in the absence of oxygen.
The process raises a fat's melting point, turning liquid
vegetable oil into products ranging from soft margarine to solid
shortening, according to the newsmagazine. When the healthful
unsaturated fats are partially hydrogenated, the double bonds
are rearranged, converting some to the trans configuration and
shifting the double bonds along the chain. Unfortunately, this
newly created trans fatty acid is an artery-clogger.
Amid the criticism of cookies, chips and other products
containing trans fat, a number of companies have either
developed foods without partially hydrogenated oils or have
pledged to explore ways of replacing the fat. PepsiCo's Frito
Lay, for example, has already eliminated trans fats from some of
Which foods contain trans fatty
Trans fats are produced commercially in large quantities to
harden vegetable oils into shortening and margarine. Food
manufacturers also use partial hydrogenation of vegetable oil to
destroy some fatty acids, such as linolenic and linoleic acid,
which tend to oxidize, causing fat to become rancid with time.
The oils used to cook french fries and other fast food are
usually this kind of partially hydrogenated oil, containing
trans fats. Commercial baked goods frequently include trans fats
to protect against spoilage. A small amount of trans fat is also
produced in the gastrointestinal tract of cattle, so that low
levels of these isomers are found in dairy and beef fat.
Commercial production of partially hydrogenated fats began in
the early 20th century and increased steadily until about the
1960s as processed vegetable fats displaced animal fats in the
diets of the U.S. and other Western countries. Lower cost was
the initial motivation, but health benefits were later claimed
for margarine as a replacement for butter.
Although the average level of trans fat in margarines has
declined with the advent of softer versions, per capita
consumption of trans fatty acids has not changed greatly since
the 1960s because of the increased use in commercially-baked
products and fast foods.
How are trans fatty acids
In clinical studies, trans fatty acids or hydrogenated fats tend
to raise total blood cholesterol levels and LDL ("bad")
cholesterol and lower HDL ("good") cholesterol when used instead
of cis fatty acids or natural oils. These changes may increase
the risk of heart disease. It's not clear if trans fats that
occur naturally have the same effect on cholesterol and heart
disease as those produced by hydrogenating vegetable oils.