Iíve recently been doing some research into Conjugated Linoleic Acid, specifically the cis 9 trans 11 isomer, after hearing of itís benefits as an anticarcinogen. Many studies done in vitro or on animals have shown C9 T11 to supress/prevent/reduce tumour growth, however all controlled studies in humans, while not specifically on cancer, seem to show negative or no effects of C9 T11. A few studies on humans show CLA to cause increased lipid peroxidation, which I would think would be a bad thing for health. See here http://www.ncbi.nlm.nih.gov/pubmed/10683436
and here http://www.ncbi.nlm.nih.gov/pubmed/10683436
and here http://www.ncbi.nlm.nih.gov/pubmed/18287358
This one showed CLA impaired endothelial function http://www.ncbi.nlm.nih.gov/pubmed/16339498
and these ones showed no benefit on immune function or blood lipids http://www.ncbi.nlm.nih.gov/pubmed/18287358 http://www.ncbi.nlm.nih.gov/pubmed/16600923 http://www.ncbi.nlm.nih.gov/pubmed/16549463
I canít find the studies right now but it also seems to induce insulin resistance in human studies as well.
Given all of this it seems to me that the poor effectiveness and negative effects of CLA in human studies does not correspond to animal or in vitro models and the majority of evidence on humans shows CLA is not beneficial and is probably detrimental. The increased lipid peroxidation is especially worrisome. Given the human evidence, is there something Iím missing? I had been including grassfed dairy in my diet because I was under the impression C9T11 was an amazing anti-cancer substance and dairy has a lot but now I feel that the evidence would lead me to take out anything I was eating solely to increase my CLA consumption. Can anyone shed some light on this? Am I missing something or am I on to something?