On the positive side, there is no robust evidence of any potentially adverse interactions (as per the p450 hepatic enzyme system) with conjugated linoleic acid (CLA). However, we are not quite in the clear.
The Tangled Tale of CLA
Although there is some provisional evidence of a potential antitumor effect, the evidence is conflicting, with even meta-analyses drawing different conclusions, and the most recent prospective cohort study from Susanna Larsson and colleagues at the Karolinska Institutet failed to find any significant protective effect of CLA against breast cancer development.
As to CLA's role in weight control, again the evidence is inconsistent, and any benefit appears to be at best small - with some loss of body fat not being associated with an associated loss in total body weight - and non-sustainable, the loss disappearing in the longer term, and the weight (!) of the evidence trends somewhat towards the conclusion that CLA reduces body fat but not body weight at least in healthy exercising humans of normal body weight, supported by the RCT of Thom and colleagues. In addition, there are some disquieting safety signals relating to a potentially adverse impact on insulin resistance, and although I am somewhat skeptical of these claims in a population of overweight or obese patients, both on grounds of study methodology as well as for empirical reasons (from the assuring results from Christian Syvertsen's robust RCT in 2006), nonetheless the effect on non-obese subjects remains unclear. Also disturbing are independent studies which suggest that CLA may adversely impair endothelial function, and may increase CRP (C-reactive protein) levels, both quite negative in impact if further confirmed.
Important: Counter Defenses
One countervailing defense I can suggest, namely concomitant resveratrol (RSV) supplementation. RSV prevents harmful and negative CLA-mediated inflammation and insulin resistance, as recently demonstrated by an ingenuous and compelling recent (2009) study from Arion Kennedy at UNC and colleagues in Germany. Now, although we don't know if RSV supplementation also protects against CLA's potentially adverse effect on CRP and endothelial function, it may be safe when consumed with the other components of the Edge-CAM regimen, as those components - especially curcumin but also EGCG, melatonin and CoQ10 - can potentially reverse these adverse events via their own powerful positive modulation of these same functions and factors.
So despite inconsistent data on any significant benefit of CLA on weight control, it is still possible that there may be some modest positive gain, and my guidance would be that against the several potentially adverse effects of CLA on cardiovascular function and risk, supplementation may be feasible without negative impact within the confines of a concurrently administrated Edge-CAM regimen.
Breast Cancer Watch