Tea and coffee consumption and risk of oral cavity cancer: results of a large population-based case-control study, the ICARE study

Oral Health and Nutraceutical Agents

Oral health is essential for both overall health and quality of life. The mouth is a window into the body's health, and nutrition can strongly impact the state of general and oral health. A healthy diet involves the synergistic effect of various nutraceutical agents, potentially capable of conferring protective actions against some inflammatory and chronic-degenerative disorders. Nutraceuticals, mostly present in plant-derived products, present multiple potential clinical, preventive, and therapeutic benefits. Accordingly, preclinical and epidemiological studies suggested a protective role for these compounds, but their real preventive and therapeutic effects in humans still await confirmation. Available evidence suggests that plant extracts are more effective than individual constituents because they contain different phytochemicals with multiple pharmacological targets and additive/synergistic effects, maximizing the benefits for oral health. Moreover, nutritional recommendations for oral health should be personalized and aligned with valid suggestions for overall health. This review is aimed to: introduce the basic concepts of nutraceuticals, including their main food sources; examine the logic that supports their relationship with oral health, and summarize and critically discuss clinical trials testing the utility of nutraceuticals in the prevention and treatment of oral diseases.

Dietary plants for oral cancer prevention and therapy: A review of preclinical and clinical studies

Oral cancer is a disease with high mortality and rising incidence worldwide. Although fragmentary literature on the anti-oral cancer effects of plant products has been published, a comprehensive analysis is lacking. In this work, a critical and comprehensive evaluation of oral cancer preventative or therapeutic effects of dietary plants was conducted. An exhaustive analysis of available data supports that numerous dietary plants exert anticancer effects, including suppression of cell proliferation, viability, autophagy, angiogenesis, invasion, and metastasis while promoting cell cycle arrest and apoptosis. Plant extracts and products target several cellular mechanisms, such as the reversal of epithelial-to-mesenchymal transition and the promotion of oxidative stress and mitochondrial membrane dysfunction by modulation of various signaling pathways. These agents were also found to regulate cellular growth signaling pathways by action on extracellular signal-regulated kinase and mitogen-activated protein kinase, inflammation via modulation of cyclooxygenase (COX)-1, COX-2, and nuclear factor-κB p65, and metastasis through influence of cadherins and matrix metalloproteinases. In vivo studies support these findings and demonstrate a decrease in tumor burden, incidence, and hyperplastic and dysplastic changes. Clinical studies also showed decreased oral cancer risk. However, high-quality studies should be conducted to establish the clinical efficacy of these plants. Overall, our study supports the use of dietary plants, especially garlic, green tea, longan, peppermint, purple carrot, saffron, tomato, and turmeric, for oral cancer prevention and intervention. However, further research is required before clinical application of this strategy.

Association of Coffee and Tea Consumption with Cardiovascular Disease, Chronic Respiratory Disease, and their Comorbidity

SCOPE

Since associations between coffee and tea consumption with cardiovascular disease (CVD) and chronic respiratory disease (CRD) remain controversial. This study aims to investigate the separate and combined associations of coffee and tea consumption with CVD, CRD, and their comorbidity.

METHODS AND RESULTS

Within the UK Biobank, 390 039 participants (56.2 ± 8.1 years) free of CVD and CRD are included. Coffee and tea consumption are self-reported at baseline. During a median follow-up of 12.1 years, 31126 CVD, 34132 CRD, and 6071 CVD-CRD comorbidity cases are identified. J-shaped associations between coffee and tea consumption with CVD, CRD, and CVD-CRD comorbidity are observed (p for nonlinearity <0.001). Compared with neither coffee nor tea consumption, hazard ratios (HRs) and 95% confidence intervals (CIs) of combined consumption of moderate coffee and tea (each 2-3 cups per day) are 0.88 (0.81-0.96) for CVD, 0.78 (0.72-0.84) for CRD, and 0.74 (0.61-0.91) for CVD-CRD comorbidity.

CONCLUSION

Moderate consumption of coffee and tea separately or in combination are associated with lower risks of CVD, CRD, and their comorbidity.

Cumulative Coffee Consumption as a Protective Factor for Head and Neck Cancer in Brazil

There is still no consensus in the literature regarding the role of coffee in head and neck cancer. Thus, we sought to analyze the cumulative consumption of coffee as a protective factor in the genesis of head and neck cancer in Brazil, one of the main coffee producing countries, from January 2011 to February 2017. We carried out a case-control study in 5 referral centers for head and neck cancer with 839 cases and 842 non-cancer hospital controls matched by sex, data collection center and age group. The results of logistic regression analysis showed that the cumulative consumption of >2 cups of coffee per day is an important protective factor (OR: 0.73, 95% CI: 0.5-0.9) against head and neck cancer. Smoking increased the risk by 22 times (OR: 22.19; 95% CI: 13.7-35.8) in individuals who smoke more than 50 packs per year, and the habit of ingesting more than 155 ml of alcohol per day represented approximately twice as high risk (OR: 2.20; 95% CI: 1.4-3.4). In summary, this study suggests that coffee consumption is associated with a lower chance of head and neck cancer.

Head and neck cancer risk factors in the French West Indies

OBJECTIVES

The incidence of head and neck squamous cell carcinoma (HNSCC) in the French West Indies (FWI) is relatively high, despite a low prevalence of tobacco smoking and alcohol drinking. Little is known about other risk factors in the FWI. We assessed associations between several factors and HNSCC risk, their population attributable fractions (PAF) in the FWI, and compared these PAFs by subsite, sex and age.

MATERIALS AND METHODS

We conducted a population-based case-control study (145 cases and 405 controls). We used logistic regression models to estimate adjusted odds-ratios (OR), PAFs and their 95% confidence intervals (CI).

RESULTS

Tobacco smoking, alcohol drinking, high-risk HPV, family history of HNC, low BMI and several occupations and industries were significantly associated to the occurrence of HNSCC. The majority of HNSCC cases were attributable to tobacco smoking (65.7%) and alcohol (44.3%). The PAF for the combined consumption of tobacco and/or alcohol was 78.2% and was considerably larger in men (85%) than in women (33%). The PAFs for the remaining risk factors were 9% for family history of HNSCC, 9% for low BMI, 15% for high-risk HPV, and 25% for occupations. The overall PAF for all risk factors combined was 89.0% (95% CI = 82.0-93.2). The combined PAFs by sex were significantly greater in men (93.4%, 95% CI = 87.5-96.5) than in women (56.4%, 95% CI = 18.7-76.6).

CONCLUSION

Tobacco and alcohol appeared to have the greatest impact on HNSCC incidence among the studied risk factors, especially among men. Prevention programs for HNSCC in the FWI should target tobacco and alcohol cessation, particularly in men. Future research should emphasise on the role of occupational factors to better understand this disease.

Association between coffee intake and the risk of oral cavity cancer: a meta-analysis of observational studies

The association between coffee intake and the risk of oral cavity cancer has been inconsistent in previous studies. Therefore, we conducted a meta-analysis to summarize the evidence regarding the strength of association between coffee intake and oral cavity cancer. PubMed, Embase, and Cochrane Library were searched to select studies on the relationship between coffee intake and oral cavity cancer conducted up to September 2018. Case-control or cohort studies and those that have reported about the effect estimates with 95% confidence intervals (CIs) of oral cavity cancer according to the different categories of coffee intake were included. The odds ratio (OR) and its corresponding 95% CI were calculated using the random-effects model. Fourteen case-control and five cohort studies that recruited 6456 patients with oral cavity cancer were included in the final quantitative meta-analysis. High versus low coffee intake was associated with a reduced risk of oral cavity cancer (OR: 0.68; 95% CI: 0.56-0.82; P < 0.001) in case-control studies (OR: 0.70; 95% CI: 0.55-0.90; P = 0.006) and cohort studies (OR: 0.65; 95% CI: 0.48-0.87; P = 0.004). Moreover, intermediate coffee intake was significantly associated with a reduced risk of oral cavity cancer (OR: 0.85; 95% CI: 0.77-0.94; P = 0.002), and such associations were mainly observed in case-control studies (OR: 0.86; 95% CI: 0.76-0.98; P = 0.021) but not in cohort studies (OR: 0.83; 95% CI: 0.67-1.02; P = 0.071). High or intermediate coffee intake might have protective effects against oral cavity cancer. However, the underlying mechanisms must be further evaluated in large-scale prospective cohort studies.

Is there any association between green tea consumption and the risk of head and neck squamous cell carcinoma: Finding from a case-control study

OBJECTIVE

Green tea consumption has been shown to reduce the incidence of head and neck squamous cell carcinoma (HNSCC) in experimental animal models, however the results from human studies are inconclusive. The aim of this study was to evaluate the relationship between green tea consumption and the risk of HNSCC.

DESIGN

The study utilised a standardised questionnaire to investigate the relationship between green tea consumption and HNSCC experience. Data about amount of green tea consumption was recorded from 147 patients with HNSCC and 263 age and gender matched controls. The results were analyzed with SPSS statistical software Version 21 using Chi- square test, and Logistic Regression (with a 95% confidence interval). Significance levels were set at 95% and p-values less than 0.05 were considered significant.

RESULTS

Statistical analysis indicated significant differences between different groups of tea consumers in terms of HNSCC risk (P < 0.001). The risk of developing oral cancer those who consume <1 cup of green tea daily was (OR = 0.29 (0.16-0.52) and for the group of > = 1 cup green tea consumers was 0.38(0.17-0.86) of those who never consume green tea (Reference point) after adjustment for other risk factors.

CONCLUSIONS

The findings support that green tea consumption may reduce the risk of HNSCC. To confirm the efficacy of green tea intake in preventing the development of HNSCC in humans further investigation is needed.

Tea consumption is associated with decreased risk of oral cancer: A comprehensive and dose-response meta-analysis based on 14 case-control studies (MOOSE compliant)

The associations of tea consumption with risk of oral cancer remain not clear. The present meta-analysis aims to clarify the real relationship between tea intake and the risk of oral cancer and quantifies the potential dose-response relationship between them.A Web search was performed within Pubmed, Embase, and Web of Science databases to identify potential studies that evaluated the relationship between tea consumption and the risk of oral cancer on Mar 21th, 2018 without language restriction. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were extracted and combined to evaluate the strength of associations. Dose-response analysis was performed to quantitate the relationship between tea intake and risk of oral cancer.Total 14 articles were included in the final analysis. The pooled OR for evaluating the risk of oral cancer and tea intake was 0.700 (95% CI = 0.609-0.805, P <.001). The linearity model of dose-response analysis indicated that with increased 1 cup daily, the risk of oral cancer decreased by 6.2% degree (OR = 0.938, 95% CI = 0.922-0.955, P <.001). Subgroup analysis indicated an inverse association between tea intake and the risk of oral cancer except subgroup analysis of black tea and American people.These results suggest tea intake provides protection against oral cancer carcinogenesis. Additionally, more large-scale pooling and high-quality studies are necessary for detecting the precise relationship between tea intake and oral cancer risk in the future.

Nomograms and risk scores for predicting the risk of oral cancer in different sexes: a large-scale case-control study

Background: Although previous studies have explored the associations of modifiable lifestyle factors with oral cancer risk, few studies integrated these factors and established predictive tools for oral cancer risk in different sexes.

Methods: Using a case-control study design, a total of 978 oral cancer cases and 2646 healthy controls were recruited in this study. Nomograms were constructed according to significant factors in multivariable logistic regression. Risk scores were calculated based on the nomograms and quantified the risk of oral cancer using restricted cubic spline.

Results: Multivariate analyses demonstrated that smoking, alcohol drinking, tea, intake of fish, seafood, vegetables, fruits, teeth loss, regular dental visits and repetitive dental ulcer were independent factors for male oral cancer. Passive smoking, age at first intercourse, cooking oil fumes exposure, tea, intake of beans, vegetables, fruits, teeth loss, regular dental visits and repetitive dental ulcer were associated with female oral cancer. Then, two nomograms were developed for predicting the probability of oral cancer in men and women with the C-index of 0.768 (95% CI: 0.723-0.813) and 0.700 (95% CI: 0.635-0.765), respectively. Restricted cubic splines graphically revealed the risk of oral cancer in individuals with different risk scores. Moreover, the risk escalated continuously with the increasing number of the risk scores among both sexes.

Conclusions: Combining nomograms with risk scores developed in this study could precisely predict oral cancer occurrence and provide an accurate risk assessment.

Independent and joint effects of tea and milk consumption on oral cancer among non-smokers and non-drinkers: a case-control study in China

This study aims to evaluate the independent and joint effects of tea and milk consumption on oral cancer risk among non-smokers and non-drinkers (NS/ND). A hospital-based case-control study was performed in Fujian, China. 421 cases and frequency-matched 1398 controls were included without tobacco smoking and alcohol drinking habits. Unconditional logistic regression model was used to assess the relationship of tea and milk consumption with oral cancer risk. Tea and milk consumption were significantly associated with decreased risk of oral cancer, the adjusted odds ratios (aORs) were 0.73 (95% CI: 0.54-0.97) and 0.69 (95% CI: 0.55-0.88), respectively. According to subgroup analysis, the inverse associations between tea consumption and oral cancer risk were only observed among the elders (>60 years) and urban residents. While the protect effect of milk drinking was more obvious in males, normal body mass index population (18.5–23.9), urban residents and those age ≤ 60 years. Additionally, a significantly multiplicative interaction between tea and milk consumption was observed for oral cancer risk (P = 0.001). The present study is the first to simultaneously assess the association of tea consumption and milk drinking with oral cancer risk. The results suggest that tea and milk consumption are independent protective factors for oral cancer among NS/ND, with a joint effect between them.

Coffee is protective against oral and pharyngeal cancer: A systematic review and meta-analysis

OBJECTIVES

Coffee is one of the most popular and consumable drinks worldwide. However, there are conflicting results on the influence of this drink in oral and pharyngeal cancer risk. To clarify this, we aimed to systemically review and carry out a meta-analysis of the relevant literature on the association between coffee and oral and pharyngeal cancer.

STUDY DESIGN

We carried out an electronic search of publications up to August 2016 from PubMed, National Library of Medicines Medline, Embase, Science Direct and the Cochrane Central Register. The Newcastle-Ottawa scale was used to address the quality of the studies a meta-analysis was carried out using random-effects models.

RESULTS

From the 22,515 entries identified in the search, 13 case-control and 4 cohort studies were selected. With regards to quality on the Newcastle-Ottawa scale, an overall value of 6.06 was obtained. The analysis for oral and pharyngeal cancer grouped together indicated a pooled OR of .69 (95% CI of .57-.84; p<.001) for high versus low coffee consumption with a moderate heterogeneity (I2: 50.3%; p=.009). Regarding studies on oral cavity cancers we observed a pooled OR of 0.82; 95% CI =.58-1.16; p=.257) and for pharyngeal cancers a pooled OR of .72 (95% CI of 0.54-.95; p=.019). There was no significant publication bias.

CONCLUSION

The results show an inverse association between high coffee consumption and the risk of oral and pharyngeal cancers, which indicates that coffee may have a protective role against these cancers. Further larger prospective observational cohort studies are needed to address any effect of other possible co-factors.

Tea consumption and its interactions with tobacco smoking and alcohol drinking on oral cancer in southeast China

BACKGROUND/OBJECTIVES

Epidemiological results on the association between tea consumption and oral cancer remain controversial. We aimed to evaluate the exact relationship between tea consumption and oral cancer in Chinese population.

SUBJECTS/METHODS

A large-scale case-control study was conducted on 586 oral cancer patients and 1024 controls frequency-matched by age and gender. Epidemiological data were collected through face-to-face interviews with a structure questionnaire. Unconditional logistic regression model was used to assess the effect of tea consumption on oral cancer stratified by smoking, alcohol drinking and demographics. Quantity of tea consumed (ml/day) was categorized into five subgroups based on quartiles and then its interactions was evaluated with tobacco smoking and alcohol drinking at each subgroup.

RESULTS

Tea consumption showed an inverse association with oral cancer for non-smokers or non-alcohol drinkers (the odds ratios (ORs) were 0.610 (95% confidence interval (CI): 0.425-0.876) and 0.686 (95% CI: 0.503-0.934), respectively). For smokers or alcohol drinkers, decreased risk was only observed in those who consumed >800 ml/day. Furthermore, oolong tea consumption was associated with decreased risk of oral cancer in smokers or alcohol drinkers but not in non-smokers or non-alcohol drinkers. Tea consumption combined with smoking or/and alcohol drinking had a greater risk than tea consumption alone, but the risk was roughly reduced from zero to Q4 (>800 ml/day). Additionally, when stratified by demographics, the protective effect of tea was especially evident in females, urban residents, normal body mass index population (18.5-23.9), farmers, office workers and those aged <60 years.

CONCLUSIONS

Tea consumption protects against oral cancer in non-smokers or non-alcohol drinkers, but this effect may be obscured in smokers or alcohol drinkers. Additionally, demographics may modify the association between tea consumption and oral cancer.

Coffee consumption associated with reduced risk of oral cancer: a meta-analysis

OBJECTIVE

Currently, there is no consensus on the effect of coffee consumption on the risk of oral cancer. We performed a meta-analysis based on published studies to uncover the association.

STUDY DESIGN

We searched PubMed (1946-2015), Embase (1976-2015), and the bibliographies of all retrieved articles for relevant citations. We performed random-effects meta-analyses of observational studies on coffee consumption and oral cancer.

RESULTS

A total of 11 case-control studies and 4 cohort studies comprising 2,832,706 controls and 5021 cases of oral cancer were included in our analysis. The results indicated that the summary odds ratio for the highest versus the lowest or no category consumption of coffee was 0.63 (95% confidence interval [CI]: 0.52-0.75). The odds ratios were 0.60 (95% CI: 0.49-0.74) for case-control studies and 0.66 (95% CI: 0.45-0.98) for cohort studies.

CONCLUSION

Overall, our results suggested that coffee consumption appears to have a protective benefit in oral cancer.

Population attributable risks of oral cavity cancer to behavioral and medical risk factors in France: results of a large population-based case-control study, the ICARE study

BACKGROUND

Population attributable risks (PARs) are useful tool to estimate the burden of risk factors in cancer incidence. Few studies estimated the PARs of oral cavity cancer to tobacco smoking alone, alcohol drinking alone and their joint consumption but none performed analysis stratified by subsite, gender or age. Among the suspected risk factors of oral cavity cancer, only PAR to a family history of head and neck cancer was reported in two studies. The purpose of this study was to estimate in France the PARs of oral cavity cancer to several recognized and suspected risk factors, overall and by subsite, gender and age.

METHODS

We analysed data from 689 oral cavity cancer cases and 3481 controls included in a population-based case-control study, the ICARE study. Unconditional logistic regression models were used to estimate odds ratios (ORs), PARs and 95% confidence intervals (95% CI).

RESULTS

The PARs were 0.3% (95% CI -3.9%; +3.9%) for alcohol alone, 12.7% (6.9%-18.0%) for tobacco alone and 69.9% (64.4%-74.7%) for their joint consumption. PAR to combined alcohol and tobacco consumption was 74% (66.5%-79.9%) in men and 45.4% (32.7%-55.6%) in women. Among suspected risk factors, body mass index 2 years before the interview <25 kg.m(-2), never tea drinking and family history of head and neck cancer explained 35.3% (25.7%-43.6%), 30.3% (14.4%-43.3%) and 5.8% (0.6%-10.8%) of cancer burden, respectively. About 93% (88.3%-95.6%) of oral cavity cancers were explained by all risk factors, 94.3% (88.4%-97.2%) in men and only 74.1% (47.0%-87.3%) in women.

CONCLUSION

Our study emphasizes the role of combined tobacco and alcohol consumption in the oral cavity cancer burden in France and gives an indication of the proportion of cases attributable to other risk factors. Most of oral cavity cancers are attributable to concurrent smoking and drinking and would be potentially preventable through smoking or drinking cessation. If the majority of cases are explained by recognized or suspected risk factors in men, a substantial number of cancers in women are probably due to still unexplored factors that remain to be clarified by future studies.

Natural Compounds: DNA Methyltransferase Inhibitors in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a multistep process which is modulated by several endogenous and environmental factors. Epigenetic changes have been found to be equally responsible for OSCC as genetic changes. A plethora of genes showing hypermethylation have been discovered in OSCC. Since these changes are reversible, a lot of emphasis is on using the natural compounds for their ability to cause demethylation which could lead to reactivation of the inactivated tumor suppressor genes. This review encompasses the promoter hypermethylation of tumor suppressor genes in OSCC and its possible reversal using natural compounds. In addition, new compounds which could be screened for their demethylating ability have also been proposed.

The role of the catecholic and the electrophilic moieties of caffeic acid in Nrf2/Keap1 pathway activation in ovarian carcinoma cell lines

In recent years, numerous studies have demonstrated the health benefits of polyphenols. A major portion of polyphenols in western diet are derived from coffee, which is one of the most consumed beverages in the world.

It has been shown that many polyphenols gain their beneficial properties (e.g. cancer prevention) through the activation of the Nrf2/Keap1 pathway as well as their direct antioxidant activity. However, activation of Nrf2 in cancer cells might lead to resistance towards therapy through induction of phase II enzymes.

In the present work we hypothesize that caffeic acid (CA), a coffee polyphenol, might act as an electrophile in addition to its nucleophilic properties and is capable of inducing the Nrf2/EpRE pathway in cancer cells.

The results indicate that CA induces Nrf2 translocation into the nucleus and consequently its transcription. It has been demonstrated that generated hydrogen peroxide is involved in the induction process. It has also been found that this process is induced predominantly via the double bond in CA (Michael acceptor). However, surprisingly the presence of both nucleophilic and electrophilic moieties in CA resulted in a synergetic activation of Nrf2 and phase II enzymes.

We also found that CA possesses a dual activity, although inducing GSTP1 and GSR, it inhibiting their enzymatic activity.

In conclusion, the mechanism of induction of Nrf2 pathway and phase II enzymes by CA has been elucidated. The electrophilic moiety in CA is essential for the oxidation of the Keap1 protein. It should be noted that while the nucleophilic moiety (the catechol/quinone moiety) can provide scavenging ability, it cannot contribute directly to Nrf2 induction. It was found that this process may be induced by H₂O₂ produced by the catechol group.

On the whole, it appears that CA might play a major role in the cancer cells by enhancing their resistance to treatment.

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The electrophilic moiety in CA is essential for the oxidation of the Keap1 protein.

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The nucleophilic moiety contribute to Nrf2/Keap1 activation via production of H₂O₂.

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CA possesses a dual activity, as inducer and as inhibitor of GSTP1 and GSR1.

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The effect of coffee on healthy subjects and cancer patients may be different.

Tea intake and risk of oral, pharyngeal, and laryngeal carcinoma: a meta-analysis

Background

The association between tea intake and risk of oral, pharyngeal, and laryngeal carcinoma is still unclear. The aim of this meta-analysis was to quantify the effect of tea consumption on the incidence of oral, pharyngeal, and laryngeal cancer to provide a better understanding on this issue.

Material/Methods

A literature search was conducted before January 2014 in MEDLINE and EMBASE databases. The relative risk (RR) estimates that extracted or calculated from all included studies were combined together. Given the existing heterogeneity in the study design and data source, a random-effects model was obtained.

Results

A total of 20 articles were included in the quantitative synthesis. Fourteen RR estimates (11 from case-control studies and 3 from cohort studies) were pooled together and the result demonstrated that tea consumption reduced the incidence of oral cancer (RR=0.85; 95% CI 0.76–0.96). The summary RR of 4 observational studies (3 case-control studies and 1 cohort study) for pharyngeal cancer was 0.87 (95% CI 0.74–1.04). The association between tea consumption and oral and pharyngeal carcinoma was reported. The summary RR for laryngeal carcinoma was 1.05 (95% CI 0.70–1.57). The Begg’s funnel plot and the Egger’s test showed no evidence of publication bias.

Conclusions

Tea consumption was associated with decreased risk of oral cancer, while no association was detected with oral/pharyngeal, pharyngeal, or laryngeal cancer.

Tea consumption and risk of head and neck cancer

Background

The current study evaluated the association between tea consumption and head and neck cancer (HNC) in Taiwan, where tea is a major agricultural product and a popular beverage.

Methods

Interviews regarding tea consumption (frequency, duration, and types) were conducted with 396 HNC cases and 413 controls. Unconditional logistic regression was performed to estimate the odds ratio (OR) and 95% confidence interval (CI) of HNC risk associated with tea drinking, adjusted for sex, age, education, cigarette smoking, betel quid chewing, and alcohol drinking.

Results

A reduced HNC risk associated with tea drinking (OR for every cup per day = 0.96, 95% CI: 0.93–0.99; OR for ≧5 cups per day = 0.60, 95% CI: 0.39–0.94) was observed. The association was especially significant for pharyngeal cancer (OR for every cup per day = 0.93, 95% CI: 0.88–0.98; OR for ≧5 cups per day = 0.32, 95% CI: 0.16–0.66). A significant inverse association between HNC and tea consumption was observed particularly for green tea.

Conclusions

This study suggests that tea drinking may reduce the risk of HNC. The anticancer property of tea, if proven, may offer a natural chemopreventive measure to reduce the occurrence of HNC.

Association of tea consumption and the risk of oral cancer: a meta-analysis

OBJECTIVES

Epidemiological studies evaluating the association of tea consumption and the risk of oral cancer risk have produced inconsistent results. Thus, we conducted a meta-analysis to assess the relationship between tea consumption and oral cancer risk.

METHODS

Pertinent studies were identified by a search in PubMed, Web of Knowledge and Wan Fang Med Online. The fixed or random effect model was used based on heterogeneity test. Publication bias was estimated using Egger's regression asymmetry test.

RESULTS

Finally, 14 articles with 19 studies comprising 4675 oral cancer cases were included in this meta-analysis. The relative risk (95% confidence interval) of oral cancer for the highest versus the lowest category of tea consumption was 0.853 (0.779-0.934), and the association was significant between oral cancer risk and green tea consumption [0.798 (0.673-0.947)] but not in the black tea consumption [0.953 (0.792-1.146)]. The associations were also significant in Asian and Caucasian.

CONCLUSIONS

Our analysis indicated that tea consumption may have a protective effect on oral cancer, especially in green tea consumption.

Chemopreventive potential of flavonoids in oral squamous cell carcinoma in human studies

Evidence available from nutritional epidemiology has indicated an inverse association between regular consumption of fruits and vegetables and the risk of developing certain types of cancer. In turn, preclinical studies have attributed the health-promoting effects of plant foods to some groups of phytochemicals, by virtue of their many biological activities. In this survey, we briefly examine the chemopreventive potential of flavonoids and flavonoid-rich foods in human oral carcinogenesis. Despite the paucity of data from clinical trials and epidemiological studies, in comparison to in vitro/in vivo investigations, a high level of evidence has been reported for epigallocatechin gallate (EGCG) and anthocyanins. These flavonoids, abundant in green tea and black raspberries, respectively, represent promising chemopreventive agents in human oral cancer.