Polyphenol supplementation as a complementary medicinal approach to treating inflammatory bowel disease

Inflammatory bowel disease (IBD) comprises a group of idiopathic chronic intestinal inflammation syndromes that are very common in developed countries. It is characterized by intermittent episodes of clinical remission and relapse, with recurrent inflammatory injury that can lead to structural damage of the intestine. The uncontrolled intestinal immune response to bacterial antigens leads to the production of abundant cytokines and chemokines, by activated leukocytes and epithelial cells, which trigger inflammatory and oxidative reactions. The current treatment of IBD consists in long-term anti-inflammatory therapy that, however, does not exclude relapses and side effects, frequently resulting in surgical intervention. Polyphenols have been acknowledged to be anti-oxidant and anti-inflammatory and therefore, have been proposed as an alternative natural approach to prevent or treat chronic inflammatory diseases. Most studies have been in animal models of colitis, using chemical inducers or mice defective in anti-inflammatory mediators and in intestinal cell lines treated with pro-inflammatory cytokines or lipid oxidation products. These studies provide evidence that polyphenols can effectively modulate intestinal inflammation. They exert their effects by modulating cell signaling pathways, mainly activated in response to oxidative and inflammatory stimuli, and NF-kB is the principal downstream effector. Polyphenols may thus be considered able to prevent or delay the progression of IBD, especially because they reach higher concentrations in the gut than in other tissues. However, knowledge of the use of polyphenols in managing human IBD is still scanty, and further clinical studies should afford more solid evidence of their beneficial effects.