From Wikipedia. How much of this is true and how much of it is bullshit?
Some studies of CLA in human diets show that it may reduce body fat, , especially abdominal fat. A maximum reduction in body fat was achieved with a daily dose of 3.4g. However,experts do not recommend taking CLA supplements. CLA supplements contain high levels of the t10,c12 CLA isomer, which has been linked to multiple side effects. Supplementation with this form of CLA has been shown to increase C-reactive protein levels, possibly to induce oxidative stress, to reduce insulin sensitivity, and to increase lipid peroxidation.
However, the significance of these findings is unknown, and other studies suggest that CLA may protect cells from oxidative damage by increasing glutathione levels without inducing lipid peroxidation. It is possible, however, that the observation of markers of increased lipid oxidation may indicate potentially desirable lipolytic effects. Further studies are necessary to establish the clinical significance of such observations.
Possible adverse effects of CLA in humans
There are concerns that the use of CLA by overweight people may tend to cause or to aggravate insulin resistance, which may increase their risk of developing diabetes. However, the evidence is controversial, and some studies showed no changes in insulin sensitivity.
In one study CLA produced a 32% increase in biliary cholesterol concentration which increases the chance of gallstone formation.
In 2006, a study by the US Department of Agriculture suggested that CLA can induce essential fatty acid redistribution in mice. Changes in docosahexaenoic acid (DHA) and arachidonic acid (AA) levels were observed in some organs. For instance, certain CLA isomers reduced the DHA content of heart tissue by 25%, while in the spleen, DHA content rose, and AA fell.
A study of CLA supplementation in hatchling chicks (2005) showed high mortality and low hatchability rates among CLA-supplemented groups, and also a decrease in brain DHA levels of CLA-treated chicks. These studies raise the question of whether CLA may increase the risk of cardiovascular and inflammatory diseases, but it has yet to be established whether such changes occur in humans, and whether they are clinically relevant.