Study on the Absorption and Urinary Excretion of Fluorine following Ingestion of Green Tea

Abstract

The concentration of fluorine in the infusion of green tea, one of the staple drinks and consumed widely in Japan, was measured. A high concentration of fluorine was found in high-class tea (Gyokuro). A larger amount of fluorine was extracted from the tea at the initial infusion than in succeeding infusions. These results suggest that the high concentration and the amaint of extraction of fluorine may be a scientific base for the selecting of good tea. From these results, it was calculated that 0.48-0.97 mg of fluorine was ingested daily from green tea by Japanese adults, and it may be considered that the tea is a main source of daily fluride intakefor them. The ingestion of green tea infusion and of sodium fluoride (NaF) solution by adult men gave the following results. That is, the absorption of fluoride from green tea is apt to be slow but it is excreted via the urine with relative rapidity, as compaired with NaF ingestion ; it is inferred that the different metabolic processes may be involved in the absorption of fluoride from green tea and from NaF. From the results of urinary excretion of fluorine, it is assumed that the urinary fluorine should be estimated with fluoride quantity of urine stored for a certain duration, since the urinary fluoride concentration varied easily with the urinary volume, the collection intervals and other conditions.