Determination of fluoride in black, green and herbal teas by ionselective electrode using a standard-addition method

Abstract

Tea leaves are very rich in fluoride, since tea plants take up fluoride from the soil and accumulate in its leaves. Some of this fluoride is released into the infusion, which is drunk as tea. Fluoride in tea could be beneficial for the prevention of dental caries, but it may result in excessive intake and lead to enamel fluorosis. The purpose of this work was to determine the fluoride levels in 12 different brands and types of tea by means of a computer-controlled ion-selective electrode potentiometry using a standard-addition method. It is a rapid method which showed good accuracy and precision. Fluoride contents of tea infusions after 5 min ranged from 0.95 to 4.73 mg/l for black teas; from 0.70 to 1.00 mg/l for green teas, and from 0.26 to 0.27 mg/l for herbal teas. It was concluded that black teas and green teas examined may be important contributors to the total daily fluoride intake. However, the ingestion of some black teas that were found to have high fluoride content by children at the age of risk to dental fluorosis should be avoided.

Risk Assessment of Fluoride Intake from Tea in the Republic of Ireland and its Implications for Public Health and Water Fluoridation

“…The purpose of the present study was to determine the fluoride concentrations in black tea infusions in the RoI, the potential dietary exposure to fluoride from tea and associated health risks. Our results demonstrate that the high fluoride levels measured in black tea prepared from packaged black tea bag products sold in the RoI are consistent with concentrations found in similar products sold in Taiwan [ 43 , 46 ]; China [ 44 , 45 ]; Poland [ 47 ]; Slovenia [ 49 ]; UK [ 51 ]; Germany [ 123 ]; Norway [ 124 ] and the USA [ 125 ].…”

Comparison of extraction and isolation efficiency of catechins and caffeine from green tea leaves using different solvent systems

“…Green tea, one of the most popular beverages consumed worldwide, has been receiving considerable interest because it contains many functional components, such as caffeine, catechins, flavonoids, fluoride and flavonol glycosides (Graham, 1992;Engelhardt et al, 2000;Yuwono, 2005). Among these constituents, catechins accounting for about 8-15% of leaf dry weight (DW) have been reported that they have beneficial medical effects on human health, including strong antioxidative, antitumor, antibacterial and antiviral effects (Kim et al, 1994;Rice-Evans, 1999;Sudano Roccaro et al, 2004;Song et al, 2005).…”

Fluoride content of retail tea bags and estimates of daily fluoride consumption from typical tea drinking in UK adults and children

“…); Taiwan mean 8.64 mg/l (Lung et al . ); and Indonesia 0.95–4.73 mg/l (Yuwono ). Our F‐ figures for black blended (4.91 mg/l) and green (3.08 mg/l) were also similar to those reported by Chan et al .…”

“…However, they were in line with estimates of F-in older (2000 mg/kg) and younger tea leaves (250-300 mg/ kg) (Fung et al 2003) and would be expected to fall within this range given that the blends would contain a variety of different leaves. F-levels in standard infusions (mean 4.91 mg/l) were in a similar range to black teas purchased in other countries: Indiamean 3.4 mg/l (Gupta & Sandesh 2012); Poland 0.12-8.33 mg/l (Kaczmarek 2004) and 0.32-4.54 mg/l (Malinowska et al 2008); International 1.15-6.01 mg/kg (Cao et al 2006); Turkey 0.57-3.72 mg/ kg (Emekli-Alturfan et al 2009); US mean 3.02 mg/l (Pehrsson et al 2011); Taiwan mean 8.64 mg/l (Lung et al 2008); and Indonesia 0.95-4.73 mg/l (Yuwono 2005). Our F-figures for black blended (4.91 mg/l) and green (3.08 mg/l) were also similar to those reported by Chan et al (2013) which were 4.64 and 3.43 mg/l, respectively, but our mean F-content for black speciality tea (3.04 mg/l) was well above Chan's mean of 1.63 mg/l.…”