Zinc bioavailability and tea consumption. Studies in healthy humans consuming self-selected and laboratory-controlled diets.

One self-selected study (study A) and one laboratory-controlled study (study B) were conducted to investigate the effect of tea consumption on zinc bioavailability in healthy humans. The 14-day study A consisted of two 7-day experimental periods, while the 28-day study B consisted of two 14-day experimental periods. In study A eight subjects and in study B ten subjects were participated. Subjects of study A consumed self-selected diets and kept a record of foods eaten. In study B, subjects ate a constant and weighted laboratory controlled diet. In both studies, subjects consumed 8 g of instant tea during tea supplementation periods. Complete urine and fecal collections were made by subjects of both studies. Zinc contents of urine, fecal and food samples were determined by using Atomic Absorption Spectrophotometer. Mean zinc intakes of humans consuming self-selected diets were below the RDA. Mean urinary zinc excretion, fecal zinc excretion and zinc balance were unaffected by the tea consumption. Negative zinc balances in study A and positive zinc balances in study B were observed in both tea and no tea dietary treatments. Tea consumption showed a small but not statistically significant adverse affect on zinc bioavailability in humans.