Dietary Tannins from Cowpeas and Tea Transiently Alter Apparent Calcium Absorption but Not Absorption and Utilization of Protein in Rats

Tannins reportedly alter absorption and utilization of protein and minerals. The present study investigated the effect of tannins extracted from «Mississippi Silver» cowpeas and black tea when incorporated into nutritionally balanced diets. Condensed tannins were incorporated into the diet of weanling male Sprague-Dawley rats at 0.0, 0.0057, 0.0171 and 0.057 g/100 g diet for 28 d. Ingestion of tannin from cowpeas or tea did not change significantly growth rate, protein efficiency ratio, apparent protein digestibility, nitrogen excretion, relative liver weight, or nitrogen concentration of liver. During d11-18, apparent calcium absorption was lower in rats fed the medium and high levels of cowpea tannin and in those fed all levels of tea tannin compared with the control group