Conjugated linoleic acid (CLA) represents a group of isomers of the essential fatty acid linoleic acid (LA, C18:2 (n-3)) that are found naturally in the meat and milk of ruminant animals. Ruminants contain micro-organisms in their rumens that are able to synthesis CLA from LA. Grass fed cows have been show to have higher concentrations of CLA in their meat and milk because the pH of their rumens becomes optimal for the relevant micro-organisms. Unlike linoleic acid which contains two cis- double bonds separated by single bond, CLA has a cis- and a trans- bond which are conjugated (on adjacent carbon atoms) (here). Experiments with adult humans suggest that supplementation with the trans-10, cis-12 and cis-9, trans-11 isomers of CLA is beneficial in weight loss1. As a result of the positive results in research, CLA has become widely available in supplemental form.
To investigate the effects of CLA on weight loss in children, researchers2 supplemented 53 prepubertal children ages 6 to 10 years with 3 grams of CLA per day for 7 months in a double-blind trial. The CLA contained 80 % of a 50:50 mix of cis-9, trans-12 and trans-10, cis-12 isomers and was administered in chocolate flavoured milk. Researchers assessed the body fat of the children using dual-energy X-ray absorptionometry. The results showed that the children supplemented with CLA had a smaller increase in body fat than the placebo group. When taken as a percentage of total body weight, the CLA group showed a reduction in percentage body fat. In addition CLA supplemented children had a decrease in abdominal body fat as a percentage of total body weight, whereas the placebo group showed an increase.
These results support previous animal experiments as well as those performed on adult humans, and suggest that isomers of CLA may have beneficial effects in the prevention of obesity. Humans can use a desaturase enzyme to manufacture CLA from trans-vaccenic acid, a trans-fatty acid found in ruminant milk and meat. The CLA and trans-vaccenic acid content of milk might therefore explain some of the association between dairy consumption and a reduced incidence of obesity. The results cited above support earlier findings that highlight the trans-10, cis-12 and cis-9, trans-11 isomers as being involved in weight control or weight loss, and therefore supplementation with CLA should aim to supply these forms. Long term consumption of CLA appears to be safe, and evidence suggests that higher intakes of the cis-9, trans-11 isomer is associated with a reduced incidence of myocardial infarction (here).
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