Dietary conjugated linoleic acid and n-3 polyunsaturated fatty acids in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a debilitating and widespread immune-mediated illness of unknown etiology. Current treatments are modestly successful and with significant side-effects. The purpose of this review is to summarize the current understanding of mechanisms of action underlying the anti-inflammatory actions of conjugated linoleic acid (CLA) and n-3 polyunsaturated fatty acids (PUFAs) in IBD.

Nutrition-based interventions that target peroxisome proliferator-activated receptors (PPARs) such as dietary CLA and n-3 PUFA have demonstrated anti-inflammatory efficacy in animal models of IBD. Clinical data on n-3 PUFA in IBD remains generally unimpressive, although results of a recent human study demonstrate that IBD remission can be maintained by maintaining the n-3: n-6 ratio more than 0.65 via n-3 PUFA intervention. In mice, CLA prevented inflammation-driven colorectal cancer by activating PPAR gamma and modulating regulatory T cells and macrophages. CLA is the subject of an ongoing clinical study in Crohn's disease patients.

Compelling evidence demonstrates that n-3 PUFA and CLA prevent or ameliorate IBD in animal models. However, this basic knowledge has not been translated into novel nutrition-based clinical interventions. For both compounds there is an urgent need for placebo-controlled, large-scale, multicenter clinical trials.