Conjugated linoleic acid
Conjugated linoleic acids ( engl. conjugated linoleic acids or CLA for short ) is a group of two polyunsaturated fatty acids is referred to the linoleic acid. This group in addition to the cis- trans isomers and positional isomers are counted with conjugated double bonds. Certain isomers of this group are mostly found in meat and dairy products from ruminants. The most common isomer is cis- 9, trans -11- CLA, one of the trans fats.
Education
CLA is formed in the rumen of ruminants, as an intermediate in the hydrogenation of linoleic acid to stearic acid, organic by linoleic acid isomerase of rumen bacterium Butyrivibrio fibrisolvens. The substrate composition in the rumen affects the range of intermediate and end products of biological hydrogenation. Characterized the content of CLA in the milk is affected. The largest percentage of CLA - isomers is in the cis -9, trans-11 form. The conversion efficiency of the CLA of milk fat is influenced by the presence of various CLA isomers. Vegetable oils are rich in linoleic and linolenic acids, which leads to increased CLA production in the rumen and in the mammary glands. The proportion of the major isomer cis- 9, trans -11 CLA is particularly increased in a grassy ( force feed poor ) feeding. Is discussed scientifically whether an additional increase in feeding on species-rich rough grazing, eg in the Alps, so in Alpine milk, takes place. However, this seems not to be the case.
Fat and milk of ruminants cells can form cis-9, trans-11 - CLA also from trans -11-18 :1- vaccenic acid (trans- vaccenic acid ) by desaturation of vaccenic acid. Even in man CLA may arise by isomerization of linoleic acid induced by anaerobic microbial activities in the gut or by free radicals. Furthermore, they can also arise from desaturation of trans- vaccenic acid. Therefore Certain tissues of the human body contain small amounts of CLA.
Effects
The European Food Safety Authority (EFSA) has positive health claims of conjugated linoleic acids examined in the context of Article 13 of Regulation ( EC) No 1924 /2006 ( Health Claims ) scientifically. In 14 of the 16 intervention studies in humans, no significant effect on body weight was observed. An effect on lean body mass (LBM ), fat-free body mass, could also not be shown. An influence on insulin sensitivity, the sensitivity of insulin receptors to insulin, sees the EFSA as being unproven. Also an antioxidant effect which protects DNA, proteins and lipids from oxidative damage, could not be detected. Stimulation of the immune system by protective antibodies against pathogens could also not be proven.