Tea has been considered as the second most widely consumed beverage on earth, after water. It was called as a “miracle drink” by the people who invented tea. The story of tea begins in China. According to legend, in 2737 BC, the Chinese emperor Shen Nung was sitting under a tree while his servant boiled drinking water, when some leaves from the tree blew into the water. Shen Nung, a famous herbalist, decided to try the infusion that his servant had accidentally created. He was surprised by the taste and the aroma of it.
Since there tea has been consuming worldwide as a medicine and then as a drink for refreshment. Ancient Chinese and Japanese medicines have emphasized the fact that green tea consumption could heal wounds and cure diseases. In 2737 BC, Chinese had a belief on tea for its healing powers. Lu Yu who was a scholar in China, who had written a treatise in AD 780, entitled Cha Ching, states that ‘tea tempers the spirits, harmonizes the mind, dispels the lassitude, relieves fatigues, awakens thought, prevents drowsiness, refreshes the body and clears the perspective faculties”( Lu Yu, Classic of Tea: Origins and Ritual) . what an elucidation!
In the ancient system of Medicine, Ayurveda had listed tea in the group of remedies as ‘rasayanas’ that bring about positive health, resistance to diseases and assured full lifespan of quality living; challenging other drugs those comes out after the disease is struck.
The medicinal value of tea and its biological effects on human health are well known now due to numerous researches done on it. Sophisticated analytical equipment combined with clinical trials have been using successfully.
Tea has shown to have various benefits on human health. Tea reduces the risk of several non-communicable diseases which have a direct relationship to the life style, including cancer, arteriosclerosis and cardiovascular diseases, neural and obesity problems, diabetes, diseases of the kidneys and liver and surprisingly it improves the oral health.
1.Chemical constituents in tea which responsible to improve oral health
- Fluorides
Tea plants are known as fluoride hyperaccumulators, which means they absorb potential toxins and heavy metals to a greater concentration than is in the soil surrounding them. The older individual tea leaves get, the more fluoride they can absorb. A substantial amount of fluoride is released during tea infusion. Soluble fluoride is easily absorbed by the gastrointestional track, the bioavailability of fluoride from tea is close to 100%, which is similar to that from drinking water. As per a study done, when tea infusions were prepared with tap water the fluoride concentration in tea infusions ranged from 1.6 to 6.1 mg/L with a mean of 3.3 mg/L[1].
- Polyphenols
Tea polyphenols, commonly known as catechins, are flavonoid compounds with a basic structure of α-phenyl-benzopyran, which is about 18% to 36% of the dry weight of tea leaves (Khan and Mukhtar, 2007). Those comprise of antioxidant properties too.
Green and black tea contain properties that reduce inflammation and prevent the growth of bacteria in the mouth. Tea also contains antioxidants such as catechins, flavonoids and Theaflavins and Thearubigins in black tea which possess anti-microbial effects.
- Zero Caloric beverage
Being a non-caloric/ zero caloric beverage, it has its unique benefit to protect the teeth from decaying.
Hence, dentists also recommend that drinks such as tea are a good alternative to soft drinks since tea is non-erosive. When selecting a drink option, it is best to go with brewed tea. Fizzy drinks and other sugar-filled beverages can cause cavities and enamel loss, which leads to declining oral health. Studies show that drinking brewed tea showed less enamel loss and more strengthening benefits for the teeth and gums.
2. How does tea improve your oral health?
Oral/dental diseases are a costly burden to health care services all around the world as it owns 5-10% of total health care expenditures which is exceeding the cost of treating some of the non-communicable diseases including cancer and cardiovascular disease in industrialized countries [7]. In low-income countries, the cost of traditional restorative treatment of dental disease would probably exceed the available resources for health care. Although not life-threatening, dental diseases have a detrimental effect on quality of life in childhood through to old age, having an impact on self-esteem, eating ability, nutrition, and health.
2.1. Dental Caries
Dental caries is a transmissible microbial disease damaging the hard tissues of teeth caused by acids released from bacterial metabolism leading to demineralization and dissolution of enamel and dentin.
The bacteria responsible of producing organic acids as a by-product of their metabolism of fermentable carbohydrates. The studies of cariostatic effects of tea were started in the 1940s and 1950s showing fluoride to be the active component . Tooth decay occurs when acid attacks the surface of the tooth. Fluoride helps repair any damage before it becomes serious. Many studies on this have proved that the tea consumption leads to reduction in dental caries in humans and experimental animals. In fact, Polyphenols and fluoride were the reason for this inhibitory effect. Green tea extracts, or polyphenols, have been reported to inhibit in vitro growth, acid production and water insoluble glucan synthesis by glucosyltransferase enzyme of Streptococcuss mutans. Similar findings have been reported for oolong tea too. In an adult human study by Wu et al. [2] rinsing with black tea ten times a day for 7 days resulted in significantly less pronounced pH fall, a lower plaque index (P < 0.05) and lower numbers of mutans Streptococci and total oral Streptococci in plaque but not in saliva. Hence, Black tea and its polyphenols may benefit human oral health by inhibition of dental plaque, acidity and cariogenic microflora too.
Another study has shown that Caries were found to be significantly lower among children who drank a cup of tea immediately after lunch and the tea polyphenols, rather than fluoride, were found to be responsible for the anticariogenic effects [3]. Another study reported that rinsing with 0.2% Chinese green tea while brushing decreased plaque and the gingival index significantly [4].
Tea extracts have also been shown to inhibit human salivary amylase and tea consumption may reduce the cariogenic potential of starch-containing foods, such as biscuits and cakes, because tea may reduce the tendency for these foods to serve as slow-release sources of fermentable carbohydrate [5]. An anticariogenic potential of black tea has been suggested in various in vitro studies too. Black tea and its polyphenols inhibited growth, acid production, metabolism and glucosyltransferase enzyme activity of Mutans Streptococci and dental plaque bacteria[6].
2.2 Tea and Gingivitis/Periodontal Disease
Periodontal disease (PD) is one of the most widespread diseases of mankind, which is also second most common oral disease worldwide, after dental caries and it’s the most common cause of tooth loss. This is a chronic condition in which a multiple and complex group of inflammatory diseases are affecting the periodontal complex i.e., tissue that surround and support the teeth (Periodontium). If someone ignores this condition, it leads further deterioration of periodontium to progressive loss of the alveolar bone around the teeth and subsequent loss of teeth [8].
Researchers have observed that for every cup of green tea consumed per day, there was a decrease in the indicators of gingival inflammation, that reduces the periodontal disease. Green tea catechin specially Epigallocatechin Gallate (EGCG) has been shown to be bactericidal against Porphyromonas gingivalis and Prevotella species in vitro. Treating with tea catechins was found to be effective in improving periodontal status. There was a reduction pocket size and the suppression of peptidase activities in the gingival crevicular fluid. Tea catechins containing the galloyl radical (Epicatechin Gallate [ECG] and Epigallocatechin Gallate [EGCG]) possess the ability to inhibit both eukaryotic and prokaryotic cell-derived collagenase, an enzyme that plays an important role in the disruption of the collagen component in the gingival tissues of patients with periodontal disease [8].
It has been proven that tea polyphenols might exert a positive influence on gingival inflammation specially among smokers.
2.3 Oral Cancer
Oral cancer is a global public health problem It is among the top 10 ranking incidence of cancers and despite the progress in research and therapy, survival has not improved significantly in the last years, representing a continuing challenge for dentistry. Oral cancer is a malignant neoplasia (an abnormal growth that can grow uncontrolled and spread to other parts of the body) which arises on the lip or oral cavity. It was traditionally defined as a squamous cell carcinoma (OSCC), as 90% of cancers are histologically originated in the squamous cells in the oral cavity [9].
Green tea polyphenols are found to induce apoptosis (programmed cell death) in many types of tumor cells, including oral cancer cells. However, how the normal cells escape the apoptotic effect has not still been understood by the researchers. The effect of extracts and polyphenols of green tea as well as [epigallocatechin-3-gallate (EGCG)] which is the most potent green tea polyphenol on normal human keratinocytes and oral carcinoma cells were assessed through assays for cell growth, invasion, combined with apoptosis. It was shown that the green tea and its constituents selectively induce apoptosis, whereas EGCG usually inhibits the growth and invasion of oral carcinoma cells.
Researchers believe that there is an inverse relationship between occurrence of oral cancer and green tea consumption according to the surveys done with Chinese and Japanese populations where we can find smokers in majority.
2.4. Plaque Development
Plaque is a sticky film forms on teeth when bacteria in the mouth mix with sugary or starchy foods. Tooth brushing and flossing get rid of plaque. If it is not removed properly, it hardens into tartar. Plaque can lead to cavities, gingivitis (gum disease) and tooth loss.
A group of researchers from the University of Illinois College of Dentistry believe that black tea and its components benefit oral healh by interfering with the harmful plaque bacteria in the mouth that cause gum disease and cavities. They report their results at the 101st General Meeting of the American Society for Microbiology in Orlando, Florida.
The British Dental Association said both black and green tea could help to combat the build-up of plaque.
2.5. Oral Thrush/ Oral Candidiasis
Oral thrush produces creamy white, sore patches in your mouth or on your tongue. Oral thrush , also called oral candidiasis is a condition in which the fungus Candida species mainly Candida albicans accumulates on the lining of your mouth.
According to a collaborative research conducted by Tea Research Institute of Sri Lanka and Faculty of Dental Sciences of University of Peradeniya, Theaflavins and Catechins in tea are highly effective on inhibition of Candida species in the oral cavity and most of the anaerobic microorganisms which produce deep pocket gingivitis [10]. In that research, both polyphenols showed anti-Candida activity against all tested Candida species; C. albicans, C. glabrata,C. parapsilosis, C. krusei and C. tropicalis. Theaflavins displayed standard post anti-fungal effect (PAFE) while catechins showed a paradoxical PAFE with all isolates of C. albicans. Standard Electron Microscopic views revealed considerable cell wall damage of C. albicans cells exposed to the polyphenols.
References
1. Declan T. Waugh, William Potter,Hardy Limeback and Michael Godfrey, Risk Assessment of Fluoride Intake from Tea in the Republic of Ireland and its Implications for Public Health and Water Fluoridation, International Journal of Environmental Research and Public Health; 13(3):259, 2016 Feb.
2. Wu C.D., Wei G., Tea as a functional food for oral health, Food Constituents and Oral Health; Current Status and Future Prospects, Woodhead Publishing Series in Food Science, Technology and Nutrition, 2009, pp. 396-417.
3. Protective Effects of Tea on Human Health, edited by Narender Kumar Jain, Maqsood Siddiqi, J. H. Weisburger, 2006.
4. Zhonghua Kou, Qiang Yi , Xue Za Zhi, Study on feasibility of Chinese green tea polyphenols (CTP) for preventing dental caries, PubMed, 1993 Jul; 28(4):197-9, PMID : PMID: 817439.
5. J. Zhang , S. Kashket, Inhibition of salivary amylase by black and green teas and their effects on the intraoral hydrolysis of starch, PubMed , 998;32(3):233-8. PMID; 10.1159/000016458
6. Smullen J, Koutsou G A, Foster H A, Zumbé A, Storey D M. ,The antibacterial activity of plant extracts containing polyphenols against Streptococcus mutans, PubMed. 2007;41(5):342-9, DOI: 10.1159/000104791, PMID: 17713333.
7. Marco A Peres , Lorna M D Macpherson , Robert J Weyant , Blánaid Daly , Renato Venturelli , Manu R Mathur, Stefan Listl , Roger Keller Celeste , Carol C Guarnizo-Herreño , Cristin Kearns , Habib Benzian , Paul Allison , Richard G Watt , Oral diseases: a global public health challenge , Lancet ,2019 Jul 20;394(10194):249-260, PMID: 31327369.
8. Aswini Y. Balappanavar, Tea and Oral Health, IntechOpen , 2020, India.
9. Kazi A, Smith D M, Daniel K, Zhong S, Gupta P, Bosley M E, Dou Q P , Potential molecular targets of tea polyphenols in human tumor cells: significance in cancer prevention , 2002 Nov-Dec;16(6):397-403, PMID: 12494882.
10. M A M Sitheeque , G J Panagoda, J Yau, A M T Amarakoon, U R N Udagama, L P Samaranayake, Antifungal activity of black tea polyphenols (catechins and theaflavins) against Candida species, Chemotherapy, 2009;55(3):189-96. PMID: 19420933.
