Some factors influencing the free fluoride content in black tea infusions

Abstract

Fluoride is an essential micro-nutrient owing to its role in the prevention of dental caries. Chronic exposure to high levels of the ion (F^-) results in both dental and skeletal fluorosis. A study was carried out to determine free fluoride content in tea (Camellia sinensis) infusions of different grades of black Cut, Tear and Curl (CTC) tea. Tea infusions, 1% w/v of 112 teas of different grades and origins, were prepared using boiling distilled water and their free fluoride contents quantified using a Fluoride Ion Selective Electrode (FISE) method. The free fluoride content of the teas was 0.37±0.04 µg F- ml-1. Infusions of tea grades BP1 and BMF gave the highest (0.40±0.22 ìg Fml^-1) and lowest (0.32±0.10 µg F^- ml^-1) free fluoride contents, respectively. There being no national and international Maxima Residue Limit (MRL) for fluoride in tea, all the teas analysed may be regarded to be safe for consumption with regard to their free fluoride contents based on the 1.5 &#181;g F^- ml^-1, World Health Organisation’s (WHO) guideline for fluoride in drinking water. Further, the effects of tea grades and area of production, on the fluoride content in tea infusions were significant (P<0.05), hence the need to enact safety guidelines and monitor continuously the fluoride levels for all types of tea products to prevent excessive intake.