Wednesday, November 01, 2006

What Are These Synthetic Trans Fats?

Are there natural trans fats?, are they as harmful as synthetic trans fats?, how much we take of each of them?

Actually, there are trans fats that occur naturally in meat and dairy products. They mainly contain the trans fatty acid " Vaccenic acid", but they are essentially harmless in the amounts encountered. They represent 15-20 % at maximum, of the trans fats we take, moreover, Vaccenic acid can be metabolized by humans to the trans isomer of Conjugated Linoleic Acid (CLA) which has a specific role in promoting health. CLA is considered to balance any harmful effect of natural trans fats. Natural trans fats have not been shown to share the harmful properties of the synthetic trans fats.

It is fair to suppose there is wide range in the toxicity in the synthetic trans isomers arising from hydrogenation of oils, and that some of these synthetic trans fats have specially high toxicity.
Then why humans synthesize these harmful trans fats?, what is the need for them?

In fact, humans do not plan to synthesize trans fats, they do their best to reduce their production, but it is difficult to prevent their formation altogether. Typically40-50% of the oil will end up as trans isomers after hydrogenation.

Food industry is concerned about shelf period as well as taste and consistency of fats. Oils are vulnerable to rancidity on storage, in addition, some trans isomers(Elaidic acid, the trans isomer of Oleic acid, the main constituent of olive oil) has a melting point has a similar temperature of the human mouth ( mouth watering?).

How I s Trans Fat Produced?
Glycerol( Glycerin) is common to all triglyceride edible fats, to this glycerol molecule, 3 fatty acid molecules are attached. The fatty acid consists of many carbon atoms, each of which is attached to the adjacent carbon by a SINGLE bond and bearing 2 Hydrogen atoms in saturated fats. I f the 2 adjacent carbons bear1 Hydrogen atom each, they coordinate to share a second bond to become bound by a DOUBLE bond, then this fatty acid is said to be unsaturated FA, if it contains more than 1 double bond, it is a polyunsaturated fatty acid.
The configuration of double bond in an unsaturated fatty acid determines the description of fatty acid, thus if the 2 Hydrogen atoms are on the same side of the Carbon chain it is a CIS isomer and this predominates naturally, in the other uncommon TRANS isomer, the 2 Hydrogen are on opposite sides of the chain.

The CIS double bond forces a kink or bend into the Carbon chain, so the unsaturated fatty acids are unable to pack closely together so readily as saturated fatty acid, and this why unsaturated fatty acids containing oils are mostly liquids at room temperature, while more saturated fats( such as Tallow) are hard. Upon hydrogenation of unsaturated fatty acid containing oil, 2 Hydrogen are bound to the vacant double-bond site removing the double bond and retaining the straight chain form and the molecule becomes more saturated.

The food industry neither needs completely hydrogenated fats which are waxy, nor it needs the polyunsaturated oils, rather it needs partially hydrogenated fats which are in between.
During hydrogenation conducted at high temperature( 260 C), the unsaturated fatty acid is subject to structural transformation. Double bonds which are naturally in the CIS configuration, can flip to TRANS configuration ( Geometrical isomers). Another possibility is that the double bond migrates along the molecular chain ( Positional isomers).

TRANS fats are involved in the pathogenesis if cardiovascular system, and lately it was found to be involved in Diabetes and Obesity.

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