International Journal of Clinical Preventive Dentistry Volume 8, Number 3, September 2012 Fluoride Content in Indian Tea (Infusions and with Milk) Audrey Madonna D'Cruz1, Shankar Aradhya2 1 A.B. Shetty Memorial Institute of Dental Sciences, Nitte University, Mangalore, 2The Oxford Dental College, Hospital and Research Centre, Bangalore, India Objective: To estimate the fluoride (F) content in prepared tea infusions and to know the effect of milk addition (varying concentration), increasing brewing time and squeezing on F content of tea. Methods: An experimental study was undertaken to determine the fluoride content in tea infusions prepared from commercially available tea in India. A total of 30 prepared samples of tea (various methods of tea preparation in India) and 1 water sample were analysed for F concentration using the F ion selective electrode method. The results were subjected to statistical analysis using the paired Student’s t-test at 95% confidence interval. Results: The F content in tea infusions with 5 mins brewing ranged between 3.37-6.2 mg/L. Addition of 10 mL milk had no effect whereas addition of 25 mL milk significantly decreased the F concentration. Increasing the brewing time by 10 mins had no effect. However, 20 mins of brewing significantly decreased the F concentration in tea infusions. It was also noted that squeezing had no effect on the F concentration in tea infusions. Conclusion: Tea consumers especially in naturally occurring high F areas should be cautious enough to limit their tea consumption to avoid the long term cumulative effects of F on health. Keywords: fluoride, tea, tea infusions, brewing, milk Introduction Fluoride (F) is an essential micronutrient. However, large quantities of F can have detrimental effects on human health (3). Tea is one of the most widely consumed drink in the world, second only to water. Tea leaves are a rich source of F. The tea plant (Camellia sinesis) takes up F from the soil and accumulates it in its leaves. “A substantial amount of F present in the leaves is released during tea infusion and nearly 94.9% of the released F is estimated to be absorbed by the body from tea infusions” (4). Hence, tea is a major source of dietary F intake. Various studies determining the concentration of fluoride in tea samples, infusions have been reported earlier in literature especially the Turkish tea, Brazilian tea, Iranian tea, German tea etc. Tea is a favorite beverage among people across the globe. However, variations do exist in the fluoride content of soil where the tea plants grow. Also, the form and method of preparation of tea or tea infusions differs across countries. The WHO report 2000 (5) has compiled data from literature and reported that fluoride concentrations in the tea infusions ranged between 0.6 to 5.0 ppm F. India is the largest producer and consumer of tea in the world Fluorine is an inactive gas element in the halogen group which has a high negative electric charge. Fluorides have been used in the dental field from the early 1940’s to prevent dental caries (1). Fluorine can inhibit bacterial generation, increase microhardness of tooth enamel, and cause fluorapatite of limited solubility created on the enamel surface to inhibit its demineralization. Moreover, since it can inhibit the bacterial metabolic process, its anticaries effect has been recognized (2). Corresponding author Audrey Madonna D'Cruz Department of Public Health Dentistry, Institute of Dental Sciences, A.B. Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore [575018], India. Tel: +91- 824-2287276, Fax: +91-9880872658, E-mail: audreydcruz @yahoo.co.in Received November, 4, 2011, Revised December, 12, 2011, Accepted September, 25, 2012 147 International Journal of Clinical Preventive Dentistry (6). Various forms of tea preparation and consumption are popular in India such as drinking tea with and without milk, boiling the tea for a longer time, squeezing tea from the leaves, so on. The objectives of this study were to estimate the F concentration in tea infusions prepared from 5 commercially available teas, to know the effect of milk addition on F content of tea and to know the effect of increasing brewing time and squeezing of prepared infusions from tea leaves on the F concentration. Material and Methods An experimental study was undertaken to determine the fluoride content in tea infusions prepared from commercially available tea in India. Five popular commercially available tea brands were selected by an independent person. The wrappers of the packets were removed, repacked and labeled A, B, C, D, and E and then handed over to the investigator to ensure blinding. In India, it is customary to boil 5 gms of tea powder in 150 mL (1 cup) of water to get a stronger cup of tea. Hence, for the study, 30 gms of each labeled pack of tea powder was added to 900 mL of boiling water and allowed to brew for 5, 10 and 20 mins and tea infusion samples were collected. Next to prepare tea, 115 mL and 100 mL were measured and poured into 2 separate plastic bottles to which 10 mL and 25 mL of milk was added respectively. Also, tea infusion 125 mL was squeezed from the leaves and collected in a separate plastic container. The entire procedure was followed for all 5 tea samples. A total of 30 tea samples and 1 water sample (used for the preparation of infusions) were coded by the investigator. F analysis was done using the Fluoride ion-selective electrode method (Orion). Statistical significance was analyzed by at 95% confidence interval by Student’s paired t-test (2 tailed) [parametric test] using SPSS software (version 11) for Windows. Results The results of the present study show that fluoride concentration in tea increases with 10 minutes brewing but significantly decrease with 20 minutes of brewing (Table 1). Addition of 10 mL of milk had no effect on fluoride concentration whereas addition of 25 mL of milk significantly decreased the fluoride concentration in tea (Table 2). Squeezing out tea leaves from the infusions had no effect on fluoride concentration (Table 3). Table 4 shows the statistical analysis of the data using Student’s t-test. Discussion Total fluoride intake depends on fluoride levels in food and beverages, while fluoride in water adds considerably to fluoride levels in prepared food (6). Tea is the most popular beverage in India, which is prepared and consumed in various forms. The study revealed that the F concentration in infusions of Indian tea brewed for 5 minutes ranged from 3.37-6.2 mgF/L. These values were higher than those reported Tokalioglu et al. (7), Table 3. Effect of squeezing on F in prepared tea infusions Table 1. F concentration in tea infusions Sample A B C D E Water sample Sample 5 mins (mg F/L) 10 mins (mg F/L) 20 mins (mg F/L) 6.2 3.59 3.74 3.95 3.37 6.29 4.49 4.77 4.23 3.55 0.14 mg F/ L 4.38 2.19 4.72 3.39 2.75 A B C D E Water sample Without squeezing (mg F/L) With squeezing (mg F/L) 6.29 4.49 4.77 4.23 3.55 8.49 6.6 5.01 4.67 2.64 0.14 mg F/ L Table 4. Statistical analysis of the data using Student’s paired t-test Table 2. F concentration in tea infusions (with and without milk) Sample A B C D E Water sample Without milk (mg F/L) 6.29 4.49 4.77 4.23 3.55 With10 mL milk With 25 mL milk (mg F/L) (mg F/L) 5.45 4.51 4.8 4.43 3.77 0.14 mg F/ L 148 Vol. 8, No. 3, September 2012 5.4 2.87 3.68 3.68 2.94 t 5 mins v/s 10 mins boiling 10 mins v/s 20 mins boiling Without milk v/s 10 mL milk Without milk v/s 25 mL milk With 10 mL milk v/s with 25 mL milk Without squeezing v/s with squeezing *t-test significant. p＜0.05. −2.569 2.894 −0.378 −4.924 3.388 −1.375 df Sig. (2-tailed) 4 4 4 4 4 4 0.062 0.044* 0.725 0.008* 0.028* 0.241 Audrey Madonna D'Cruz and Shankar Aradhya：Fluoride in Indian Tea Mahvi et al. (8), Yuwano (9) wherein F concentration in tea infusions ranged between 0.64-3.55 mgF/L (Turkish tea), 0.53+ 0.07 to 2.60+0.18 mgF/L (Iranian tea), and 0.95-4.73 mgF/L (German tea) respectively. Sergio Gomez et al. (10) reported a mean concentration of 2.36 mgF/L at the first 5 minutes in Chile tea infusions. These variations may be due to differences in sample sources such as leaf age, maturity and genetics of plant, type of soil and climate so on. In this study, addition of 10 mL of milk had little effect on F concentration in tea but addition of 25 mL of milk significantly decreased the F concentration. Cao et al. (11) have reported that milk addition has no effect on F concentration in tea. However, the authors did not mention the quantity of milk added to the infusions. The fact that calcium in milk chelates with F ions may be the reason for low concentration of F on milk addition to tea. This study revealed that increasing brewing time 20 mins significantly decreased F concentration in tea infusions. The reason may be that with increase in time, F from infusion may combine with other ions like magnesium, etc. resulting in a decrease in free F concentration. Also there may be loss of negligible amount of F into the atmosphere. Squeezing of prepared infusions from tea leaves had no significant effect on F concentration in tea infusions. Possibly, all the F in the tea leaves was released into the infusion and there was no available F in the tea leaves. Various brands of tea are available in India. However, only 5 popular brands of tea (black tea) were considered in this study which is a limitation of this study. The F concentration in other types of tea like the green tea or herbal teas also needs to be determined. Also, further research has to be done into whether the addition of fluoridated water for preparation of tea has an effect on the fluoride level in tea. Conclusion Considering the results of the present study, a cup of tea (150 mL) without milk provides 0.53-0.94 mgF (mean 0.64 mgF) and with milk provides 0.45-0.8 mgF (mean 0.58 mgF). Moreover, this study was conducted with water containing 0.14 mg/L of F. If water with high levels of naturally occurring F used, the F concentration in tea would be higher than the current findings. The WHO report 2000 (5) has reported that various foodstuffs prepared with fluoridated water may contain a fluoride concentration of 0.6-1 mg/kg as compared to the usual concentration of 0.2-0.3 mg/kg. Hayacibara MF (12) reported the amount of fluoride found in one bag of Brazilian black tea ranged from 0.08 to 0.40 mg F/cup and the fluoride concentrations in the infusions ranged between 0.8 to 4.0 ppm F. Hence tea consumers especially in naturally occurring high F areas (Andhra Pradesh, Karnataka, Rajasthan) should be cau- tious enough to limit their tea consumption to avoid the long term cumulative effects of F on health. In addition, in some localities where the dose of fluoride is close to the optimal one, tea drinking would initiate fluorotic lesion (13). It is recommended that F concentration should be clearly printed on the packets of tea containers by the manufacturers and should be made mandatory. Acknowledgement We thank Dr. M. V. Shashirekha, Chief Chemist (Mineral), Department of Mines and Geology, Bangalore for her valuable assistance in analyzing the tea samples. References 1. Ham MY, Shin SC, Park KS, Cho JW. Caries prevention effect on fluoride topical application and mouth rinsing. Int J Clin Prev Dent 2006;2(1):7-17. 2. Kim HJ, Lee CH, Park JH, Chung YB. Fluoride uptake on the tooth enamel according to application method. Int J Clin Prev Dent 2009;5(1):39-47. 3. World Health Organization. Water, Sanitation and Health: Guidelines for drinking water quality: Vol 2. Health criteria and other supporting information. 2nd ed. World Health Organization, Geneva 1996:231-7. 4. Hudaykuliyev Y, Tastekin M, Poyrazoglu ES, Baspinar E, Velioglu YS. Variables affecting fluoride in turkish black tea. Fluoride 2005;38(1):38-43. 5. 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