Antioxidant and anti-cancer properties have been attributed to CLA, and studies on mice and rats show encouraging results in hindering the growth of tumors in mammary, skin, and colon tissues.It has been reported that CLA can up-regulate the tumor suppressor gene PTPRG, and may have anti cancer properties. A European team led by the Swiss scientist Lukas Rist has found that mothers consuming mostly organic milk and meat products have about 50 percent higher levels of rumenic acid in their breast milk. 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, some 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.In contrast, the cis-9,trans-11 CLA isomer, the primary form of CLA found naturally in beef and dairy products, has been shown to 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.