Dietary grape seed tannins: effects of nutritional balance and on some enzymic activities along the crypt-villus axis of rat small intestine.

The aim of the study was to determine the nutritional and intestinal effects of grape seed tannins. For this purpose, tannins were incorporated in diets of rats at levels of 0.2 or 2.0% for 31 days in comparison to a control diet. The animals were pair-fed. Nutritional balances were not affected by feeding 0.2% tannins. At the highest dose (2%) grape seed tannins reduced growth as well as dry matter (DM) and nitrogen (N) digestibility. In rats fed protein-free diets, 2% tannins significantly increased endogenous fecal N. Starch and fat were well digested in all groups of rats. No changes in organ weights were observed. Duodenal alkaline phosphatase activity (AP) was never affected by tannins. On the other hand, in the jejunum, along the vilus-crypt unit, a reduction of AP and sucrase appeared at the tip villus which was balanced by an enhancement of 3H-thymidine incorporation in the middle of the crypt zone, giving evidence of endogenous N loss. This study did not reveal a major toxic effect of tannins except a reduced DM and N digestibility; nevertheless tannins directly interfere with mucosal proteins, thereby stimulating the cell renewal.