Dietary fiber, low-molecular-weight food constituents and colo-rectal inflammation in animal models -- a review.

This review provides an overview over studies in experimental animals aimed at elucidating the influence of dietary constituents on colo-rectal inflammation. Human studies as well as in vitro investigations will not be covered. In experimental animals, a variety of chemical treatments and genetic modifications, lead to various types of gut inflammation. In a number of these models, there is good evidence for an anti-inflammatory action of dietary tocopherols, certain polyphenols, and curcumin at relatively high oral doses. It has also been established, that oral application of fats and oils rich in n-3 PUFAs and/or conjugated linoleic acid (CLA) can attenuate certain types of colitis in experimental animal models. While the effect of dietary calcium on experimental colitis is less clear, there are hints indicating that certain high-fiber diets or diets rich in digestion-resistant carbohydrates ("fiber") can attenuate experimental colitis in animals, although contradictory results have been reported. In summary, the anti-inflammatory potency of dietary constituents on colon inflammation in experimental animals seems to be rather limited. The reasons for this lack of activity seem to be manifold including pharmacokinetic limitations and intestinal degradation of the compounds, in particular insufficient local, i. e., intra- or sub-mucosal levels of the effective compounds, and general limitations of animal models.