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Conjugated linoleic acid (CLA) consists of 18 carbon atoms and double bonds, the same chemical formula as linolenic acid (C18: 2). Double bonds in CLA are conjugated fatty acids (separated by a single bond rather than two as in linolenic acid). The double bonds in CLA isomers may be in positions 8 and 10 or 9 and 11 or 13 and 11.

In addition to the possible locations of the double bond, this fatty acid can have different geometric configurations due to cis-trans isomerism. The total number of possible isomers is 16.

Biosynthesis of CLA occurs naturally in ruminants, using a bacterial fermentation enzyme linoleic acid provided by the bacteria Butyrovibrio fibrisolvens. During the process, a predominant form cis9trans11-CLA isomer (rumenic acid), while the other 15 isomers have been identified in milk fat represents between 15% and 22% CLA.

Another source of CLA in ruminants is the synthesis of delta9-desaturase via trans-11 octadecenoic acid.

Natural sources in the diet

The major source of CLA in humans, in adipose tissue, is due to milk and its derivatives. There is a positive correlation between dietary fat and CLA in milk fat. Other sources in the diet are ruminant meat and small amounts in other foods high in fat, such as: chicken, pork, salmon and egg yolks.

In a normal diet, the CLA intake estimated from 20 to 70 mg per day. The serum level of CLA in humans is between 20 and 70 micromoles per liter, of which cis9trans11 isomer represents 80% and trans10-cis12 10%.

The CLA is marketed is usually produced synthetically, from sunflower oil heated in a basic medium. The final content of CLA fatty acids depends on the amount of linoleic acid in original oil. Most products consist of the four isomers trans8cis10, cis9trans11, trans10cis12 and cis11trans13. In most fatty acids CLA products displayed in three ways, recent developments have been found as triglycerides.

Contained in commercial products

Tonalin ® is one of the most widespread, cis9trans11-CLA represents up to 39% and trans10cis12-CLA isomer accounts for 41% of GDP. 5% consists of other isomers, cis9cis11-CLA, cis10trans12-CLA and 7.9-CLA isomers, 8-10CLA and 11,13-CLA. Besides oil Tonalin ® CLA is about 0.5% linoleic acid, oleic 5.5% and 4% of unidentified fatty acids.

Other trademarks has a slightly different composition of isomers, but the relationship between trans10cis12 cis9trans11 and is close to 1 in most synthetic products on the market.

Cis11-trans13 isomer accumulates in the liver and pig heart muscle, so that manufacturers are trying to decrease its amount. However reaches up to 15% of CLA in some preparations.

Dosage and use

Most marketed CLA recommend a daily dose of 2 to 3.4 grams, which can lead to a contribution of isomers trans10cis12 cis9trans11 and between 1.6 and 2.7 grams daily.

One of the typical arguments that give the producers to deceptively convince consumers is that these fatty acids occur naturally in food, but that modern food production methods leave a very small amount as consuminos .

This statement can be justified to some extent with cis9trans11 isomer, but not for trans10cis12. This isomer occurs naturally in very low concentrations and daily intake is estimated at 4 to 34 mg per day. When taking 3.4 grams of Tonalin ® (as recommended by a well known Spanish dairy industry), this isomer is ingested 70 times the amount made naturally. The isomer cis9trans11 ingested in this way, about 10 times the usual diet.

The contra-indicated by the manufacturer of Tonalin ® refers to the recommendation desaconsjea consumption in pregnant women, although other marketers do not tell. As discussed in the second part of this article, Tonalin ® has beneficial effects and merchants that advertise have not been proven scientifically.