Seedlings of the tea plant, Camellia sinensis (L.), were grown hydroponically for 30 days to study the effect of fluoride (F) on the chemical composition and minerals in the leaves. Polyphenols, total catechins, and protein decreased significantly with increasing exposure to F. Except for epigallocatechin, most of the monomeric catechins also decreased significantly. These changes are not considered beneficial. On the other hand, the content of amino acids and soluble- sugars increased significantly, but the differences in caffeine and water-soluble extracts were not statistically significant. Except for magnesium and manganese, the uptake of most of minerals was inhibited, whereas the content of F increased markedly. These results suggest that the main chemical constituents of tea leaves decreased under F treatment and that individuals who consume these teas may ingest excessive amounts of F. Therefore, the direction of our further study will be to find ways to reduce the levels of F in tea plants.
The tea plant takes up F from the soil and accumulates it in its leaves where it becomes a major source of F. As seen in Table 3, F content in tea leaves showed an increasing tendency as its concentration in the nutrient solution increased with a very high positive correlation (r=0.9667, p<0.01). A substantial amount of F is released during tea infusion and nearly all (about 94.9%) of the released F is absorbed by consumers (27).
Since there is increasing evidence that F exposure may actually increase the risk of tooth decay as well as dental fluorosis (28), it is desirable to seek and develop measures to reduce F levels in tea plants. Also worth noting is the fact that early- stage skeletal as well as dental fluorosis in children has been traced to high-F brick tea (29), and adult skeletal fluorosis has been reported from excessive consumption of instant tea with 3.3 ppm F (30).