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 min erals. 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 int o 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 w eight, or nitrogen concentration of liver. During d 11-18, apparent ca lcium absorption was lower in rats fed the medium and high levels of c owpea tannin and in those fed all levels of tea tannin compared with t he control group. By wk 4, no differences were observed in apparent ca lcium absorption among treatment groups. Apparent magnesium absorption was not affected by dietary treatment, nor was femur content of calci um or magnesium. We conclude that at the levels of condensed tannins f ed, a short-term reduction of apparent calcium absorption occurred; ho wever, by wk 4 calcium absorption was comparable to that of the contro l group. The acute change that occurred in apparent calcium absorption did not influence bone calcium content.