Date of Submission
Campus Only Senior Thesis
Bachelor of Arts
Dr. Donald McFarlane
Dr. Sarah Gilman
The tea plant, Camellia sinensis, is a fluoride (F) accumulator. Upon brewing, tea releases large amounts of F. Excessive amounts of F can cause dental fluorosis (DF) and skeletal fluorosis (SF). This study aims to determine the F levels in 4 brands of green tea and 4 brands of black tea. F was measured using an ion selective electrode (ISE) in 3 analyses: i) standard tea infusion, ii) infusion over time with spectrophotometric determination, and iii) microwave digestion. By considering the existing literature and the results of this study, the health risk associated with consuming these 8 brands of tea is evaluated.
In accordance with the literature, black tea infusions have significantly higher F than green tea infusions (p < 0.01). As the brew with the significantly highest F concentration (4.07 mg L-1 ), Tetley was chosen to demonstrate the relationship between infusion time and F concentration. As expected, both F concentration and absorbance increase with infusion time. The microwave digestion results are less conclusive. There is no significant difference between the dry mass of F (mg kg-1 ) in green and black tea. Across all samples, approximately 10-31% of the total F is released after 2 minutes of infusion.
These results suggest that chronic tea consumption could cause DF and SF. A cup of Tetley tea contains 0.81 mg of F. Only 7.4 or 2.2 cups of Tetley tea would need to be consumed by an adult or child, respectively, to exceed the daily upper limit at which symptoms of SF can arise. Considering the multiple other dietary fluoride sources and the increased susceptibility of children, F in tea should be more closely monitored.
Shelley, James, "Investigating the Fluoride Content in Black and Green Tea" (2019). CMC Senior Theses. 1998.
This thesis is restricted to the Claremont Colleges current faculty, students, and staff.