Habitual tea consumption protects against the inhibitory effects of tea on iron absorption in rats

Abstract

The hypothesis of this study was that tea inhibits iron absorption in animals unaccustomed to tea consumption but not in animals habituated to high intakes of tea. Three diets were prepared: 1) tannin-free diet; 2) 5% tea solids (tea) diet; and 3) 5% tea solids + 6% gelatin (T/G). Gelatin was chosen as a proxy for salivary proline–rich proteins (PRP). Five groups of rats were assigned to the following treatments: 1) control (tannin-free diet throughout), 2) short-term tea (tannin-free except tea diet on day 8, 3) long-term tea (tea diet throughout), 4) short-term T/G (tannin-free except tea with gelatin diet on day 8, and 5) long-term T/G (tea with gelatin diet throughout). After 10 days of dietary treatment, iron absorption, measured using 59Fe, was 41%, 7%, 25%, 7%, and 21% for treatments 1, 2, 3, 4, and 5, respectively. Rats in groups 3 and 5 showed higher PRP than control. We conclude that rats possess adaptive mechanisms for partially overcoming the inhibitory effects of tannins on iron absorption possibly by increasing secretion of PRP in saliva.