Fluoride and pH of Tea Beverages Commercialized in the U.S.

Objectives: Tea has become a popular drink in western diets. Since fluoride content and pH can exert an impact on dental caries and dental erosion, but no such information is available in the product labels, we determined the fluoride concentration and pH in tea beverages commercialized in the U.S.
Methods: Commercialized tea beverages (n=460) were acquired from fifteen different grocery-stores and coffee-shops in the Chicagoland area. Tea infusions (prepared 1 tea-bag or 2.0±0.05 g in 200 mL of boiled deionized-water for 5 min) or solutions ready-to-drink were evaluated in duplicate. Previously calibrated fluoride-ion selective electrode and pH electrode were used for sample analyses. Fluoride and pH were compared among tea types (n=7) and flavor (n=8) categories using multiple comparison tests (p<0.05). Additionally, 4 samples (containing 0.7-1.6-3.2-6.5 µg/mL) were prepared in triplicate with fluoridated tap-water.
Results: Commercial tea products exhibited a large variation in fluoride and pH (fluoride= 1.49±1.51 µg/mL [mean±SD]; min.0.00- max.8.95; pH= 4.88±0.94; min.2.60- max.6.97). Fluoride and pH appeared not to be correlated (Pearson test, r=0.094; p=0.04). Black (2.56±1.57 µg/mL F; n=149), green (1.79±1.14 µg/mL F; n=130), and oolong tea (2.72±0.59 µg/mL F; n=5) presented the highest F-concentrations, while, herbal infusions (0.06±0.19 µg/mL F; n=141) the lowest. Green (pH=5.14±0.85), herbal (pH=4.95±1.13) and oolong (pH=5.25±0.19) tea presented the highest pHs, while fruit flavored tea (pH=4.20±0.99; n=86) the lowest. A 98.7%, 68.9% and 25.4% of samples had pH <6.3, <5.5 and <4.5, respectively. Samples prepared with fluoridated tap-water (0.74±0.002 µg/mL) increased fluoride-content by 0.76±0.01 µg/mL regardless of tea F-concentration measured in deionized-water.
Conclusions: Most tested tea had a pH that can potentially increase the risk of dental erosion. Despite variations among brands, most black and green tea were a natural source of fluoride, while herbal infusions did not provide significant concentrations of fluoride. Fluoridated tap-water appeared to have an additive effect on F-concentration of tea-infusions.