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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 5  |  Issue : 2  |  Page : 68-73

Determination of the Fluoride Content of Malaysian Commercial Teas


1 Paediatric Dentistry and Dental Public Health Department, Kulliyyah of Dentistry, International Islamic University Malaysia, Pahang, Malaysia
2 Dental Department, Ministry of Health Malaysia, Pahang, Malaysia
3 Fundamental Dental and Medical Sciences Department, Kulliyyah of Dentistry, International Islamic University Malaysia, Pahang, Malaysia
4 Restorative Dentistry Department, Kulliyyah of Dentistry, International Islamic University Malaysia, Pahang, Malaysia
5 Pharmaceutical Technology Department, Kulliyyah of Pharmacy, International Islamic University Malaysia, Pahang, Malaysia

Date of Submission06-Nov-2020
Date of Decision18-Mar-2021
Date of Acceptance09-Apr-2021
Date of Web Publication23-Jun-2021

Correspondence Address:
Yunita Dewi Ardini
Paediatric Dentistry and Dental Public Health Department, Kulliyyah of Dentistry, International Islamic University Malaysia, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang.
Malaysia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/SDJ.SDJ_56_20

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  Abstract 

Background: Tea ranks first as the most-enjoyed beverage worldwide. Nevertheless, tea is rich in fluoride due to its uptake and storage from the soil by tea plants. Moreover, limited information is available regarding the fluoride content of Malaysian teas. Objective: This study aims to quantify the amount of fluoride present in teas available in the Malaysian market. Methods: An exploratory research was conducted on commercially available infusion teas from Peninsular Malaysia between November 2016 and December 2017. The fluoride content of 106 tea samples from three groups, viz., black, green, and other tea types, respectively, was measured using ultraviolet–visible spectrophotometry. The results were analyzed by one-way analysis of variance and independent t-test. Results: All of the tea leaf samples contained fluoride content between 0.01 and 1.08 mg/L. Black, green, and red tea exhibited significantly different contents of fluoride (P = 0.028). Conclusion: Significant amounts of fluoride were present in teas found in Malaysian markets. Our study provides Malaysian consumers key information regarding the amount of fluoride present in their teas.

Keywords: Dental caries, fluoride, herbal infusion, oral health, tea infusion


How to cite this article:
Ardini YD, Asri ZM, Azhar MM, Lestari W, Kusumawardani A, Haris MS. Determination of the Fluoride Content of Malaysian Commercial Teas. Sci Dent J 2021;5:68-73

How to cite this URL:
Ardini YD, Asri ZM, Azhar MM, Lestari W, Kusumawardani A, Haris MS. Determination of the Fluoride Content of Malaysian Commercial Teas. Sci Dent J [serial online] 2021 [cited 2021 Jul 31];5:68-73. Available from: https://www.scidentj.com/text.asp?2021/5/2/68/319050




  Background Top


Fluoride is an abundant mineral naturally found in soil, water, and food. Adequate intake (AI) of fluoride has been recognized to decrease the occurrence of dental caries in children and adults.[1] Nevertheless, excess intake of fluoride can exert adverse effects. Consumers are advised to consume fluoride with a content less than its recommended probable toxic dose of 5 mg/kg to avoid side effects, such as nausea, vomiting, and gastric pain.[2] The World Health Organization (WHO) has recommended a safe fluoride content of less than 1.5 mg/L in drinking water. Drinking water with a fluoride value greater than this concentration poses a higher risk for developing dental fluorosis.[3]

Fluoride exerts a surface effect on erupted teeth; thus, an anticaries effect can be achieved by the daily exposure of teeth to a small amount of fluoride. Furthermore, increased patient exposure to fluoride is a risk factor for caries.[4] In addition, systematically ingested fluoride affects hard tissue development via its incorporation into the enamel, making it more resistant to the acids produced by the bacteria in caries.[5] However, if an excess amount of fluoride is consumed during development, it can lead to the formation of porosities in the enamel. This excess fluoride consumption results in dental fluorosis, which is observed as spots on the enamel ranging from faint white to dark in color. Dental fluorosis spots affect the appearance and structure of the tooth surface. In addition, fluorosis occurs in the bone and manifests as increased bone weight, which is inferior in quality and strength compared with those of normal bones.[6],[7]

Beverages are one of the most common sources of fluoride, and a majority of the population receives their fluoride supply via the addition of fluoride to the general water supply.[8],[9] The Malaysian government implemented the fluoridation of water since 1972. The Ministry of Health, Malaysia recommends a fluoride content of 0.5–0.9 mg/L,[10] whereas WHO recommends a fluoride content between 0.7 and 1.2 mg/L in water.[3] Water is the most consumed drink worldwide, followed by tea.[11] Several types of teas are available and categorized according to their fermentation level. Unfermented tea is also known as green tea (0% fermentation), whereas completely fermented tea is known as black tea (80–100% fermentation). Teas fermented between 10% and 70% are considered to be semi-fermented.[12]

Several researchers have reported that tea infusions generally contain a relatively high fluoride concentration.[13],[14],[15],[16],[17] In Turkey, black tea has been reported to contain 0.57–3.72 mg/L of fluoride.[18] Several studies have reported 26–808 mg/kg fluoride in teas processed from young leaves.[19],[20],[21],[22] The popularity of tea may be attributed to the systemic health benefits reported from its consumption. In agreement with the growing health and wellness trend in Malaysia, an increasing number of consumers are consuming tea for its health benefits. Several studies have recommended consuming a large amount of tea daily to realize its health benefits. Several studies have reported a lower risk of cardiovascular disease and stroke in persons who consume more than two cups of black tea daily.[23],[24],[25] One study has reported that green tea contains the antioxidant epigallocatechin-3-gallate that destroys the mitochondria and arrests cancer cell proliferation.[26]

High fluoride levels in teas have been recorded in several countries. In Norway, a significant increase in dental fluorosis has been associated with an elevated fluoride content of 0.50 mg/L in drinking water.[27] Similar observations have been reported in the North Americas (United States and Canada), as well as in Chile.[27],[28],[29],[30],[31] Greater than 4.32 mg/L of the content of fluoride in water has been linked to the increased incidence of total bone and hip injuries.[32] Moreover, significantly lower intelligence quotient scores have been reported in children living in Chinese villages with a high content of fluoride (4.12 mg/L) in their water supply compared with those living in other villages.[33]

Malaysian people consume large quantities of teas available in the market, but studies focussing on the fluoride content of these teas have not been reported. Currently, studies regarding the determination of the fluoride content of teas that are available in the Malaysia market have not been reported. Hence, we sought to investigate the fluoride content of teas available commercially in Malaysia. In this study, the concentration of fluoride present in black tea, green tea, and other teas (oolong, white, Pu-erh, and herbal) was examined to increase the awareness of tea consumers regarding the effects of tea consumption on their health.


  Materials and Methods Top


A total of 106 samples of popular commercial teas sold in major supermarkets in West Malaysia were analyzed. Samples were collected for 6 months from December 2016 to May 2017. Canned/bottled, ready-to-drink teas that are widely available as convenience drinks in the Malaysian market were not included in this study. This study was conducted at the Dental Polyclinic, Kulliyyah of Dentistry, International Islamic University Malaysia between November 2016 and December 2017.

Tea bags containing the sample (i.e., black tea, green tea, and other teas, such as oolong, white, Pu-erh, and herbal) were weighed using a laboratory scale (LYC® Precision Portable Lab Electronic Balance XY-2C, China). Warm distilled water (85°C) was added to each sample teabag in a cup. The volume of distilled water added was calculated and adjusted before mixing based on the weight of the teabag to ensure that all tea samples had the same concentration (20 g/L). The tea bag was then left to infuse inside the cup for 5 min before being removed.

An ultraviolet–visible spectroscopy (UV–VIS) spectrophotometer (320–1100 nm, Spectroquant®; Merck Millipore, Darmstadt, Germany) was employed to measure the fluoride content. A fluoride standard (Merck) was used to prepare a standard curve prior to each batch analysis. One milliliter of the fluoride reagent (Hach SPADNS2; Hach Co., Loveland, CO, USA) was added to 5 mL of each tea sample. The solution was swirled until well mixed. Then, 1 mL of the solution was pipetted into a cuvette, which was placed in the spectrophotometer cassette. Measurement and interpretation were performed according to the manufacturer’s manual.

Statistical analysis

Data were analyzed by using SPSS software (IBM SPSS Statistics for Windows, Version 23.0, SPSS Inc., Chicago, IL, USA). One-way analysis of variance and independent t-test were used for comparison between the three and two groups, respectively. Significant differences were reported when the P-value was less than 0.05.


  Results Top


In the study, all 106 tea samples were found to contain fluoride. [Table 1] lists the fluoride content of each tea based on geographical origin. Tea from Thailand exhibited the highest mean fluoride content (0.73 mg/L), whereas that from the UK exhibited the lowest average fluoride content of 0.04 mg/L. Malaysian teas ranked sixth for the highest fluoride content at 0.44 mg/L.
Table 1: Fluoride concentrations in tea from different countries

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[Table 2] lists the average fluoride concentration (mg/L) of the samples. The teas were further divided into black, green, and other teas (viz., oolong, white, Pu-erh, and herbal tea). The fluoride levels in the infused black tea ranged from 0.01 to 1.08 mg/L [Table 1], those in the green tea ranged from 0.01 to 0.82 mg/L, whereas in the other teas (viz., oolong, white, Pu-erh, and herbal tea), the fluoride content ranged from 0.13 to 0.53 mg/L. A significant difference was observed in the fluoride levels in black and green teas (P = 0.033 < 0.05). An analysis of the result also revealed a positive difference (0.145), in which the fluoride content of black tea was greater than that of green tea. The fluoride content of black and the other teas did not differ significantly (P = 0.074 > 0.05). Similarly, the fluoride content was not significantly different between the green tea and other teas (P = 0.715 > 0.05).
Table 2: Fluoride content of the tea samples measured

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  Discussion Top


Fluoride provides several benefits such as the remineralization of tooth structure, strengthening of tooth structure via fluorapatite crystal formation, and reducing acid production by plaque bacteria.[34],[35] These functions of fluoride aid in halting the progression of caries and prevent the occurrence of new caries. Only a moderate amount of fluoride is required to achieve such benefits of fluoride. All of our tea samples contained fluoride. This result is in agreement with other studies reported worldwide.[13],[14],[15],[17],[18],[19],[20],[21],[22] The uptake of fluoride from the soil and air occurs via the tea bush, Camellia sinensis; thereafter, fluoride is stored as ions in tea leaves.[19],[20],[34],[35] Tea leaves that are used for brewing release fluoride into the surrounding solution. Tea is one of the sources of fluoride consumed by the population other than salt, processed foods and beverages, and dental products.[34],[36]

In this study, the highest fluoride concentration of 1.08 mg/L was recorded. This value is well within the AI value of fluoride per day, which is 0.05 mg/kg/day, particularly for people who consume a normal amount of fluoride from other sources.[37] According to the 2003–2004 Malaysian Adults Nutritional Survey (MANS), 47% of the Malaysians drink tea twice a day.[10] Thus, if one tea bag is used for one cup of tea, the total daily fluoride consumption by almost half of the Malaysian population purely from tea is still within the recommended value. However, most of the Malaysian states add fluoride to their water supply, and tea that is made using fluoridated drinking water may have a higher fluoride content.

Herein, the average fluoride value recorded was 0.6 mg/L. This value is less than those reported in similar studies from Malaysia (13.3 mg/L),[36] Indonesia (1.95 mg/L),[38] India (3.14 mg/L),[29] Republic of Ireland (2.5 mg/L),[39] Taiwan (5.95 and 5.37 mg/L),[12],[13] China (2.11 mg/L),[20] and Iran (1.2 and 3.575 mg/L).[40],[41] These differences in the fluoride content are most probably related to differences in the methodology and variations in the used tea leaves, including leaf age, maturity, soil type, geographical origin of the tea plant, and water used for irrigation, during the determination of the fluoride content of tea samples.[20],[34],[36] The results determined that the fluoride content of black tea is greater than that of green tea (P = 0.033 < 0.05). This result is in agreement with other studies.[34],[38] Nevertheless, research from Slovenia reported no significant differences among average fluoride concentrations in black, green, oolong, and Pu-erh teas.[12]

Herein, spectrophotometry was employed to estimate the fluoride content of tea. This method saves time as the fluoride determination process is simple, and it is suitable for triplicate analysis of greater than 100 tea samples within a limited time. In contrast, other researchers have employed the conventional ion-selective electrode and ion chromatography methods. Unfortunately, these methods require a longer operational time.[14],[15] Two studies compared the fluoride results between ion chromatography and spectrophotometry and concluded no significant differences between the two methods. Still, a standardized method to measure fluoride levels is not available, which hinders the adoption of safe fluoride levels in tea beverages.[34]

Differences in brewing time also notably affected the amount of fluoride released from the tea.[34],[42] The brewing time in our study was maintained constant at 5 min to simulate the usual tea brewing duration by most consumers. Furthermore, this duration is also thought to produce the best tea flavor with the marginal unpleasant taste of tannins.[35],[36] Nevertheless, several tea enthusiasts love to brew a larger amount of tea leaves for an extended period. Hence, people who brew tea for a longer time may ingest more fluoride and potentially increase their daily intake of fluoride more than the recommended value. The U.S. National Academy of Sciences, Institute of Medicine, has recommended an AI of 0.05 mg F/kg body weight/day of fluoride from all sources, which is defined as the estimated intake that has been proven to reduce the maximum occurrence of dental caries in a population without causing unwanted side effects, including moderate dental fluorosis.[3] Fluoride content in tea is in safe range; hence, it can be included in dietary advice as a source of fluoride for its benefits to dental health.


  Conclusion Top


In conclusion, fluoride was detected in all infusion teas sourced commercially in Malaysia. Tea from Thailand exhibited the highest mean fluoride content of 0.73 mg/L, whereas tea from the UK exhibited the lowest average fluoride content of 0.04 mg/L. Malaysian teas ranked sixth for the highest fluoride content at 0.44 mg/L. Valuable information regarding the levels of fluoride present in tea infusions was provided to the Malaysian tea-drinking population. Furthermore, according to this study, it is recommended to consider brewing time and tea packaging as key factors contributing to fluoride content in tea. These factors will require superior analysis methods to compare the differentiating factors.

Acknowledgements

We are grateful to Brother Muzammil Zuberdi from Kulliyyah of Science, International Islamic University Malaysia for his valuable guidance during completion of this research.

Financial support and sponsorship

This work was not supported financially.

Conflicts of interest

The authors declare no conflicts of interest.



 
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