Fluoride in black and green tea (Camellia sinensis) infusions in Ethiopia: measurement and safety evaluation
The fluoride contents in the infusions of 21 commercially available Ethiopian and imported black and green tea brands; in leaf and bag forms was determined by a fluoride ion-selective electrode method. Of the samples analyzed twelve were products from Ethiopia and the remaining nine were imported tea brands. The effect of brewing time on fluoride release from tea was assessed. Results showed that fluoride release increased with increasing brewing time (3, 5 and 10 min). Fluoride level after 5 min brewing for black tea leaves, green tea bags, and black tea bags was in the range of 117–682 mg/kg, 111–190 mg/kg and 141–246 mg/kg, respectively. The WHO guideline for daily fluoride intake is 2 mg for children and 4 mg for adults. Assuming that one consumes 4 cups of tea everyday (400 mL) and each cup uses 2.5 g of tea leaves, the daily fluoride intake from black tea leaves may be in the range between 1.11 and 6.82 mg. For the same condition, if consumption of one green tea bag is considered, the fluoride intake can be in the range between 1.00 and 1.38 mg. Similarly, intake from the black tea bags may range from 0.86 to 1.81 mg. Considering the Ethiopian black tea alone, the daily fluoride intake may range from 2.48 to 6.82 mg. Thus according to the WHO recommendation for daily fluoride intake and ignoring other possible sources; the black and green tea bags and imported black tea leaves are safe for all age groups. None of the 10 Ethiopian black tea leaf brands are safe for children but 30% of the analyzed samples are safe for adults.
KEY WORDS: Black tea infusion, Green tea infusion, Fluoride intake, Brewing time, Safety evaluation
Bull. Chem. Soc. Ethiop. 2010, 24(3), 327-338.