Determination of fluoride content in teas and herbal products popular in Poland.

Abstract

Fluoride level, due to its narrow therapeutical range, must be constantly monitored in beverages, especially in daily-consumed plant infusions. Fluoride is important for prevention of tooth decay and osteoporosis, but its excess leads to fluorosis. Since tea can selectively absorb fluorides from soils, the question arises if a long-term consumption can pose an adverse effect on human health. Infusions of 33 popular teas (black, green, white, earl grey, pu-erh), tea-like products (rooibos, yerba mate) and herbs (chamomile, mint, nettle, purges, yarrow) available in the Polish market were analyzed with respect to a fluoride level by means of a validated ion-selective electrode method, which is proven to be fast and reliable. Significantly different fluoride concentrations in infusions were observed, with black tea on top, where extraction of fluoride is the highest (average 2.65mg F-/L, range 0.718-6.029mg/L). Two-fold higher fluoride contents were measured in infusions made from black tea bags than from leaves (average 3.398mg/L and 1.529mg/L, respectively). Green teas released comparable amounts of fluoride as black teas, while in herbal extracts the fluoride content was negligible. The rank with respect to the fluoride concentration in an infusion is as follows: black tea > green tea > earl grey > pu-erh > white tea>>>rooibos, yerba mate, herbal products. Increasing of brewing time results in an increased fluoride content, but the overall content of fluoride in the analyzed infusions of teas and herbs was not high enough to cause a risk of fluorosis, even if left to brew up to 15min.