Background:

Conjugated linoleic acid (CLA) refers to a family of eight geometric isomers of linoleic acid in which the two double bonds are contiguous. (The predominant form of linoleic acid in nature, 18:ω6, has double bonds at nine and 12, interrupted by a methylene carbon.) CLA is found in both meat and dairy products, but it is not found to any significant degree in plants. The predominant isomer of CLA in animal tissue is 9Z,11E; smaller amounts of 10E,12Z also occur. Various antioxidant and antitumor activities have been attributed to CLA or its downstream metabolites.[1] Reported health benefits of dietary supplementation with CLA have been attributed variously to competitive inhibition of Δ6-desaturase and/or PPARγ activation.[2]

Reference:
[1]. Shultz, T.D., Chew, B.P., Seaman, W.R., et al. Inhibitory effect of conjugated dienoic derivatives of linoleic acid and β-carotene on the in vitro growth of human cancer cells. Cancer Letters 63, 125-133 (1992).
[2]. Houseknecht, K.L., Vanden Heuvel, J.P., Moya-Camarena, S.Y., et al. Dietary conjugated linoleic acid normalizes impaired glucose tolerance in the Zucker diabetic fatty fa/fa rat. Biochemical and Biophysical Research Communications 244, 678-682 (1998).