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REVIEW ARTICLE
Year : 2015  |  Volume : 5  |  Issue : 2  |  Page : 46-49

Green tea: Its potential health implications and other benefits


1 Department of Public Health Dentistry, Sri Aurobindo College of Dental Sciences, Sri Aurobindo Institute of Medical Science (SAIMS), Indore, Madhya Pradesh, India
2 Department of Oral Medicine and Radiology, Kalinga Institute of Dental Sciences (KIDS), Bhubaneswar, Odisha, India

Date of Submission05-Dec-2014
Date of Acceptance22-Jan-2015
Date of Web Publication23-Mar-2015

Correspondence Address:
Swati Balsaraf
B-204, Akanksha Apartment, Sri Aurobindo Institute of Medical Science (SAIMS) Staff Quarters, Behind Aurobindo Hospital, Indore-Ujjain Road, Indore - 453 555, Madhya Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2231-0738.153791

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   Abstract 

Green tea has always been considered by the Chinese and the Japanese as a potent medicine for the maintenance of health, endowed with the power to prolong life. The health-promoting properties of the tea plant are often attributed to the active ingredients that include polyphenols. Ultimate antioxidative and bioactive potential of green tea in vivo is dependent on the absorption, distribution, metabolism, and excretion (ADME) properties of the catechins within the body after ingestion and the reducing properties of the resulting metabolites. It has antibacterial, antifungal, anticancerous, anticaries, antiperiodontitis properties; is effective for weight loss; and also arrests the exacerbation of pulpitis. Clinical applications of these potential benefits warrant further investigation through scientifically sound research prior to any definitive statements. The article was aimed to review the dental benefits of green tea as very few articles are documented. The literature was searched through Google search engine, EBSCOhost, and PubMed Central. Data were collected and the articles pertaining to dental implications were selected for this article.

Keywords: Anticancerous, antioxidant, flavanols, free radical scavenging activity (FRSA), green tea catechins (GTCs), reactive oxygen species (ROS)


How to cite this article:
Balsaraf S, Chole R. Green tea: Its potential health implications and other benefits. Int J Nutr Pharmacol Neurol Dis 2015;5:46-9

How to cite this URL:
Balsaraf S, Chole R. Green tea: Its potential health implications and other benefits. Int J Nutr Pharmacol Neurol Dis [serial online] 2015 [cited 2019 Oct 13];5:46-9. Available from: http://www.ijnpnd.com/text.asp?2015/5/2/46/153791


   Introduction Top


Green tea has always been considered by the Chinese and the Japanese as a potent medicine for the maintenance of health, endowed with the power to prolong life. [1] The tea plant (Camellia Sinensis) has been grown in Southeast Asia for thousands of years and is now cultivated in more than 30 countries around the world. [2] Health benefits of tea catechins in cancer have been broadly attributed to one of the three areas: Antioxidant properties, the effects on intestinal microflora and nutrient absorption, and the effects on metabolism and metabolic enzymes affecting the growth of cancer cells. [3] For the first time, in 1989, it was demonstrated that Japanese green tea has an inhibitory effect on Streptococcus mutans. [4]


   The tea flavanols and its chemistry Top


The health-promoting properties of the tea plant are often attributed to the active ingredients that include polyphenols. [2] Tea flavanols are a group of natural polyphenols (epicatechins) found in green and black tea. Four flavanol derivatives are found in tea: Epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). [3],[4],[5],[6],[7],[8],[9],[10] Tea catechins are characterized by the dihydroxyl or the trihydroxyl groups on the B ring and the meta-5,7-dihydroxy groups on the A ring. The B ring appears to be the principal site of antioxidant reactions. The antioxidant capacity of polyphenols in vivo is due to several factors:

  1. Radical scavenging activity,
  2. Metal ion chelating effect,
  3. Stability of the resultant radical formed after scavenging,
  4. pH sensitivity, and
  5. Solubility in the lipophilic phase. [8]


Ultimate antioxidative and bioactive potential in vivo is dependent on the absorption, distribution, metabolism, and excretion (ADME) properties of the catechins within the body after ingestion and the reducing properties of the resulting metabolites. Biotransformation of catechins leads to the formation of glucuronide and sulfate conjugates and methylated metabolites. The gastrointestinal (GI) tract plays a very important role in the metabolism and bioavailability of green tea catechins (GTCs) before they reach the liver. GTCs and their metabolites formed in the small intestine are transported back to the intestinal lumen, which reach the large intestine where they are further metabolized into small phenolic acids and valerolactones by the gut microflora. They may be reabsorbed or passed out in the feces. [11] According to one recent report, the cytotoxic action of the plant-derived polyphenols may involve mobilization of endogenous copper and consequent prooxidant action. [12]


   Functions Top


Antioxidant property

Green tea enhances humoral and cell-mediated immunities, decreasing the risk of certain cancers and cardiovascular diseases. Much of the cancer chemopreventive properties of green tea are mediated by EGCG and it has been assumed that it induces apoptosis and promotes cell growth arrest by altering the expression of cell cycle regulatory proteins. [2] EGCG is a valuable scavenger of reactive oxygen species (ROS), such as superoxide radical, singlet oxygen, hydroxyl radical, peroxyl radical, and peroxynitrite; is important in promoting carcinogenesis; and has strong antioxidant activity. It protects cellular damage by inhibiting DNA damage and the oxidation of low-density lipoprotein (LDL) and many putative health benefits of tea are presumed to be caused by its antioxidant effects. [2] In a study done by Atsumi et al. (2007), consumption of green tea increased the free radical scavenging activity (FRSA) (P < 0.05). [13]

Anticancerous property

Multiple cell signaling pathways have been shown to be affected by EGCG: Inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), insulin-like growth factor-1 receptor (IGF-1R) activation, cyclooxygenase-2 (COX-2) expression, mitogen-activated protein kinases (MAPK) pathways, epidermal growth factor receptor (EGFR) mediated pathways, proteasome activity, vascular endothelial growth factor (VEGF), and matrix metalloproteinase-2 (MMP-2) and MMP-9. [6] In a study done by Nakamura et al. (2010), there were no significant associations between intakes of alcohol, coffee, green tea and the risk of pancreatic cancer death. [14] Green tea might be protective against stomach cancer, [15] colorectal cancer, lung cancer as well as its premalignant lesions. However, some studies indicate no relationship between gastric cancer, colorectal cancer, lung cancer and green tea consumption. For oral cancer and pharyngeal cancer, there was a tendency for a decreased risk in women consuming more than five cups of green tea per day when compared with those drinking less than one cup daily. [16] The interactions between cells and extracellular matrix (ECM), which promote adhesion and migration, are believed to be essential for invasion, migration, and metastasis of tumors. MMPs play a crucial role in the process of cancer invasion and metastasis. The expressions of MMP-2 and MMP-9 of oral cancer-derived cells (OC2 cells) are reduced by EGCG treatment in a dose-dependent manner. [17]

Anticaries property

Tea is a herbal substance with anticaries property; the inhibitory effect of green tea on tooth decay has been reported. The result of a study done by Naderi et al. shows that Iranian green tea has an inhibitory effect on Streptococcus mutans. [4]

Antiperiodontitis property

Lipopolysaccharide (LPS) stimulates inflammatory cells, such as neutrophils, macrophages, and fibroblasts, to secrete interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNFα) (2-4), and these mediators have been reported to accelerate osteoclast formation and bone resorption potently in vivo and in vitro. GTC had an inhibitory effect on osteoclastic bone resorption and osteoclast formation in the presence of receptor activator of nuclear factor kappa-B ligand (RANKL) both in vivo and in vitro. These inhibitory effects of GTC may have utility as a prophylactic and therapeutic agent for inflammatory bone diseases such as periodontitis. [18] Porphyromonas gingivalis possesses potent virulent factors such as cysteine proteases, which include Arg-gingipain (Rgp) and Lys-gingipain (Kgp). In a study done by Okamoto et al. (2004), the results suggested that tea catechin derivatives exhibited inhibitory activity against Rgp and to a lesser extent against Kgp of P. gingivalis. [19]

Against candidiasis

The green tea polyphenols significantly decreased the ability of C. albicans to grow and sustain biofilms. Further investigation on the possible effects that these polyphenols had on C. albicans metabolism implicated proteasome involvement. The tea catechins may also affect other metabolic pathways besides proteasome disruption in C. albicans, preventing the normal signals for growth and development of biofilm infections. [5]

Against leukoplakia

In a double-blind intervention trial performed by a group from Beijing in China, 29 out of 59 patients with oral leukoplakia were randomized to use a mixed tea extract orally as well as a topical tea extract. After the 6-month trial, the oral lesions had decreased in size in almost 40% of the patients treated, which was associated with a decrease in proliferation in the treatment group on histopathologic examination (P < 0. 05). [6]

Against pulpitis

Many types of cytokines and adhesion molecules are responsible for the initiation and progression of pulpitis. Dental pulp cells (a major cell type in the dental pulp) also have the capacity to produce proinflammatory cytokines, such as IL-6 and IL-8, and express adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in response to inflammatory stimuli, including the bacterial component. In the present study, the authors showed that the catechins EGCG and ECG inhibit the expression of proinflammatory cytokines and adhesion molecules in human dental pulp cells (HDPC) treated with LPS and peptidoglycan (PG). These findings suggest that GTCs may arrest the exacerbation of pulpal inflammation. [20]

Antibacterial effect

GTCs inhibit the growth of various bacteria, showing their antibacterial effects. Recently, a comparative study revealed that the minimal inhibitory concentration of EGCG was much lower than that of EC and that EGCG caused more intensive damage of the membranes compared with EC, indicating the importance of a galloyl moiety for the effects of catechins. Catechins and green tea extracts show minimal inhibitory concentrations ranging 100-1,000 Μmol/L against various bacteria. In an oral pharmacokinetic study, catechins were found to maintain the Μmol/L concentrations in human saliva after oral application of green tea extracts. At the corresponding concentration levels, all the eight catechins reduced membrane fluidity. [21]


   Other benefits Top


Weight management

Several small clinical trials have investigated the effects of green tea on weight loss and weight management. Some controlled trials suggest a benefit from green tea, whereas others do not. None of the studies demonstrate persistent effects. [22]

Gargling effect

Gargling with a catechin extract of green tea-inhibited influenza infection and application of green tea extract to the oral or nasal cavities suppressed various pathogenic bacteria. [23]

Antithyroid effect

A study done by Sakamoto et al. (2001) suggests that the dietary administration of the green tea extract catechins in high doses induced goiters in rats, which may be due to the antithyroid effects of the catechins. [24]

Adverse effects

There are several case reports of hepatotoxicity linked to green tea extract products in the form of pills or beverages. The mechanism for this is unknown. Allergic reactions have been reported for topical green tea ointment, which may cause cervical and vaginal inflammation, irritation, and vulvar burning. [22] Tea is generally safe, with a few caveats. In large amounts, it can interfere with blood clotting and thus may interact with warfarin (Coumadin) and other blood thinners. Tea can also impede the absorption of iron from fruits and vegetables. Adding lemon or milk to the tea or drinking it between meals will counteract this problem. Tea also contains caffeine, albeit in smaller amounts than coffee. [25] Evidence suggests that the adverse effects primarily include GI and central nervous system (CNS) disturbances. [16]


   Conclusion Top


One 8-ounce cup of brewed green tea typically has up to 200 mg of EGCG. Green tea and its catechins may open up new vistas of therapeutic avenue because of its anti-inflammatory and antioxidant potential. The catechins in tea have antibacterial action against Streptococcus mutans and Streptococcus sobrinus. Although the evidence on the degree of activity is limited and varied, it does suggest that these catechins may have inhibitory and bactericidal actions. Green tea polyphenols may have chemopreventive effects in the prevention and management of oral leukoplakia. Clinical applications of these potential benefits warrant further investigation through scientifically sound research prior to any definitive statements regarding the chemopreventive effects or anticaries activity of this tea.

 
   References Top

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Béliveau R, Gingras D. Green tea: Prevention and treatment of cancer by nutraceuticals. Lancet 2004;364:1021-2.  Back to cited text no. 1
    
2.
Butt SM, Sultan MT. Green tea: Nature′s defense against malignancies. Crit Rev Food Sci Nutr 2009;49:463-73.   Back to cited text no. 2
    
3.
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4.
Naderi NJ, Niakan M, Kharazi Fard MJ, Zardi S. Antibacterial activity of Iranian green and black tea on streptococcus mutans: An in vitro study. J Dent (Tehran) 2011;8:55-9.  Back to cited text no. 4
    
5.
Evensen NA, Braun PC. The effects of tea polyphenols on Candida albicans: Inhibition of biofilm formation and proteasome inactivation. Can J Microbiol 2009;55:1033-9.  Back to cited text no. 5
    
6.
Klass CM, Shin DM. Current status and future perspectives of chemoprevention in head and neck cancer. Curr Cancer Drug Targets 2007;7:623-32.  Back to cited text no. 6
    
7.
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8.
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[PUBMED]  Medknow Journal  
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13.
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Ho YC, Yang SF, Peng CY, Chou MY, Chang YC. Epigallocatechin-3-gallate inhibits the invasion of human oral cancer cells and decreases the productions of matrix metalloproteinases and urokinase-plasminogen activator. J Oral Pathol Med 2007;36:588-93.  Back to cited text no. 17
    
18.
Nakamura H, Ukai T, Yoshimura A, Kozuka Y, Yoshioka H, Yoshinaga Y, et al. Green tea catechin inhibits lipopolysaccharide-induced bone resorption in vivo. J Periodontal Res 2010;45:23-30.  Back to cited text no. 18
    
19.
Okamoto M, Sugimoto A, Leung KP, Nakayama K, Kamaguchi A, Maeda N. Inhibitory effect of green tea catechins on cysteine proteinases in Porphyromonas gingivalis. Oral Microbiol Immunol 2004;19:118-20.  Back to cited text no. 19
    
20.
Nakanishi T, Mukai K, Yumoto H, Hirao K, Hosokawa Y, Matsuo T. Anti-inflammatory effect of catechin on cultured human dental pulp cells affected by bacteria-derived factors. Eur J Oral Sci 2010;118:145-50.  Back to cited text no. 20
    
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Tsuchiya H. Effects of green tea catechins on membrane fluidity. Pharmacology 1999;59:34-44.  Back to cited text no. 21
    
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24.
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25.
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