J. Vallet et al., DIETARY GRAPE SEED TANNINS - EFFECTS ON NUTRITIONAL BALANCE AND ON SOME ENZYMATIC-ACTIVITIES ALONG THE CRYPT-VILLUS AXIS OF RAT SMALL-INTESTINE, Annals of nutrition & metabolism, 38(2), 1994, pp. 75-84
The aim of the study was to determine the nutritional and intestinal e
ffects of grape seed tannins. For this purpose, tannins were incorpora
ted in diets of rats at levels of 0.2 or 2.0% for 31 days in compariso
n to a control diet. The animals were pair-fed. Nutritional balances w
ere not affected by feeding 0.2% tannins. At the highest dose (2%) gra
pe seed tannins reduced growth as well as dry matter (DM) and nitrogen
(N) digestibility. In rats fed protein-free diets, 2% tannins signifi
cantly increased endogenous fecal N. Starch and fat were well digested
in all groups of rats. No changes in organ weights were observed. Duo
denal alkaline phosphatase activity (AP) was never affected by tannins
. On the other hand, in the jejunum, along the villus-crypt unit, a re
duction of AP and sucrase appeared at the tip villus which was balance
d by an enhancement of H-3-thymidine incorporation in the middle of th
e 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 dige
stibility; nevertheless tannins directly interfere with mucosal protei
ns, thereby stimulating the cell renewal.