Black tea consumption and risk of rectal cancer in Moscow population

Lower Relative Contribution of Positive Family History to Colorectal Cancer Risk with Increasing Age: A Systematic Review and Meta-Analysis of 9.28 Million Individuals

OBJECTIVES

Existing algorithms predicting the risk of colorectal cancer (CRC) assign a fixed score for family history of CRC. Whether the increased CRC risk attributed to family history of CRC was higher in younger patients remains inconclusive. We examined the risk of CRC associated with family history of CRC in first-degree relative (FDR) according to the age of index subjects (<40 vs. ≥40; <50 vs. ≥50; and <60 vs. ≥60 years).

METHODS

Ovid Medline, EMBASE, and gray literature from the reference lists of all identified studies were searched from their inception to March 2017. We included case-control/cohort studies that investigated the relationship between family history of CRC in FDR and prevalence of CRC. Two reviewers independently selected articles according to the PRISMA guideline. A random effects meta-analysis pooled relative risks (RR).

RESULTS

We analyzed 9.28 million subjects from 63 studies. A family history of CRC in FDR confers a higher risk of CRC (RR = 1.76, 95% CI = 1.57-1.97, p < 0.001). This increased risk was higher in younger individuals (RR = 3.29, 95% CI = 1.67-6.49 for <40 years versus RR = 1.42, 95% CI = 1.24-1.62 for ≥40 years, p = 0.017; RR = 2.81, 95% CI = 1.94-4.07 for <50 years versus RR = 1.47, 95% CI = 1.28-1.69 for ≥50 years, p = 0.001). No publication bias was identified, and the findings are robust in subgroup analyses.

CONCLUSIONS

The increase in relative risk of CRC attributed to family history was found to be higher in younger individuals. Family history of CRC could be assigned a higher score for younger subjects in CRC risk prediction algorithms. Future studies should examine if such approach may improve their predictive capability.

An inverse association between tea consumption and colorectal cancer risk

It is well known that the tea extracts, mainly polyphenols as chemo-preventive elements, could act as cancer progression blockers. Although the association between tea consumption and colorectal cancer risk has been widely investigated, the results still remain inconsistent. We conducted a dose-response meta-analysis to evaluate their relationships by enrolling qualified 29 literatures. The summary odds ratio (OR) of colorectal cancer for the highest vs. lowest tea consumption was 0.93 with 0.87–1.00 of 95% confidence intervals (CIs) among all studies with modest heterogeneity (P = 0.001, I² = 43.4%). Stratified analysis revealed that tea, especially green tea, had a protective effect among female and rectal cancer patients. Particularly, the dose-response analysis showed that there was a significant inverse association between an increment of 1 cup/day of tea consumption and colorectal cancer risk in the subgroup of the green tea drinking (OR = 0.98, 95% CI = 0.96–1.01, P_nonlinear = 0.003) and female (OR = 0.68, 95% CI = 0.56-0.81, P_nonlinear < 0.001). Our findings indicate that tea consumption has an inverse impact on colorectal cancer risk, which may have significant public health implications in the prevention of colorectal cancer and further similar researches.

Pharmacological Intervention through Dietary Nutraceuticals in Gastrointestinal Neoplasia

Neoplastic conditions associated with gastrointestinal (GI) tract are common worldwide with colorectal cancer alone accounting for the third leading rate of cancer incidence. Other GI malignancies such as esophageal carcinoma have shown an increasing trend in the last few years. The poor survival statistics of these fatal cancer diseases highlight the need for multiple alternative treatment options along with effective prophylactic strategies. Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high intake of certain dietary agents in their regular meals have lower cancer rates. Thus, an impressive embodiment of evidence supports the concept that dietary factors are key modulators of cancer including those of GI origin. Preclinical studies on animal models of carcinogenesis have reflected the pharmacological significance of certain dietary agents called as nutraceuticals in the chemoprevention of GI neoplasia. These include stilbenes (from red grapes and red wine), isoflavones (from soy), carotenoids (from tomatoes), curcuminoids (from spice turmeric), catechins (from green tea), and various other small plant metabolites (from fruits, vegetables, and cereals). Pleiotropic action mechanisms have been reported for these diet-derived chemopreventive agents to retard, block, or reverse carcinogenesis. This review presents a prophylactic approach to primary prevention of GI cancers by highlighting the translational potential of plant-derived nutraceuticals from epidemiological, laboratory, and clinical studies, for the better management of these cancers through consumption of nutraceutical rich diets and their intervention in cancer therapeutics.

Green tea consumption and colorectal cancer risk: a report from the Shanghai Men's Health Study

Tea and its constituents have demonstrated anticarcinogenic activity in both in vitro and in vivo animal studies. Results from epidemiologic studies, however, have been inconsistent. Some factors that coexist with tea consumption, such as cigarette smoking, may confound or modify the association between tea consumption and cancer risk. The objective of this study was to comprehensively evaluate the association between green tea consumption and colorectal cancer risk in a population-based prospective cohort study, the Shanghai Men's Health Study. The analysis included 60,567 Chinese men aged 40-74 years at baseline. During ∼5 years of follow-up, 243 incident cases of colorectal cancer were identified. Multivariable Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of developing colorectal cancer. Regular green tea consumption (ever drank green tea at least three times per week for more than six consecutive months) was associated with reduced risk of colorectal cancer in non-smokers (multivariable-adjusted HR = 0.54, 95% CI: 0.34-0.86). The risk decreased as the amount of green tea consumption increased (P(trend) = 0.01). Each 2 g increment of intake of dry green tea leaves per day (approximately equivalent to the amount of tea in a tea bag) was associated with a 12% reduction in risk (HR = 0.88, 95% CI: 0.78-0.99). No significant association was found among smokers (HR = 0.94, 95% CI: 0.66-1.34). This study suggests that regular consumption of green tea may reduce colorectal cancer risk among non-smokers.

A thought on the biological activities of black tea

Tea is the most widely used ancient beverage in the world and black tea possesses many biological effects on the organisms. It acts as an effective antioxidant because of its free radical-scavenging and metal-chelating ability. Due to this, it is active against inflammation, clastogenesis, and several types of cancer. Tea reduces DNA damage and mutagenesis due to oxidative stress or the presence of pro-mutagens through antioxidant function, blocking activation pathways of mutagens, suppressing transcription of enzymes involved etc. Inhibition of low-density lipoprotein (LDL) peroxidation, suppression of fatty acid synthase etc., suggest that tea may have a role in preventing cardiovascular diseases. Some epidemiological studies support the protective role of black tea against cardiovascular diseases but some do not. Besides, black tea has beneficial effects on the gastrointestinal tract; it affects motility, absorption, microflora etc., by influencing the hormonal balance and antioxidant function black tea improves bone mineral density. It is also antiviral due to its enzyme-inhibiting and receptor-blocking properties. Although its role in cancers of the gastrointestinal tract, liver, and prostate is confirmed, its effect against urinary tract cancer is uncertain and further studies are required. Apart from these, excess consumption may lead to the formation of a stained pellicle layer on teeth, which is difficult to eliminate, inhibits trypsin, influences mineral absorption, causes convulsions etc. Excess caffeine intake may have adverse effects on selected organs as reported in studies on some organisms. These reports indicate that there is a wide scope of further research for the efficient use of black tea active conserves/isolates to reap health benefits.

Green and black tea consumption and risk of stroke: a meta-analysis

BACKGROUND AND PURPOSE

Experimental models of stroke provide consistent evidence of smaller stroke volumes in animals ingesting tea components or tea extracts. To assess whether a similar association of black or green tea consumption with reduced risk is evident in human populations, we sought to identify and summarize all human clinical and observational data on tea and stroke.

METHODS

We searched PubMed and Web of Science for all studies on stroke and tea consumption in humans with original data, including estimation or measurement of tea consumption and outcomes of fatal or nonfatal stroke. Data from 9 studies involving 4378 strokes among 194 965 individuals were pooled. The main outcome was the occurrence of fatal or nonfatal stroke. We tested for heterogeneity and calculated the summary effect estimate associated with consumption of >or=3 cups of tea (green or black) per day using random-effects and fixed-effects models for the homogeneous studies. Publication bias was also evaluated.

RESULTS

Regardless of their country of origin, individuals consuming >or=3 cups of tea per day had a 21% lower risk of stroke than those consuming <1 cup per day (absolute risk reduction, 0.79; CI, 0.73 to 0.85). The proportion of heterogeneity not explained by chance alone was 23.8%.

CONCLUSIONS

Although a randomized clinical trial would be necessary to confirm the effect, this meta-analysis suggests that daily consumption of either green or black tea equaling 3 cups per day could prevent the onset of ischemic stroke.

Prospective cohort study of green tea consumption and colorectal cancer risk in women

Tea and its constituents have shown anticarcinogenic activities in in vitro and animal studies. Epidemiologic studies, however, have been inconsistent. We prospectively evaluated the association between green tea consumption and colorectal cancer (CRC) risk in a cohort of 69,710 Chinese women aged 40 to 70 years. Information on tea consumption was assessed through in-person interviews at baseline and reassessed 2 to 3 years later in a follow-up survey. During 6 years of follow-up, 256 incident cases of CRC were identified. The multivariate relative risk of CRC was 0.63 (95% confidence interval, 0.45-0.88) for women who reported drinking green tea regularly at baseline compared with nonregular tea drinkers. A significant dose-response relationship was found for both the amount of tea consumed (Ptrend = 0.01) and duration in years of lifetime tea consumption (Ptrend = 0.006). The reduction in risk was most evident among those who consistently reported to drink tea regularly at both the baseline and follow-up surveys (relative risk, 0.43; 95% confidence interval, 0.24-0.77). The inverse association with regular tea drinking was observed for both colon and rectal cancers. This study suggests that regular consumption of green tea may reduce CRC risk in women.

Black tea--helpful or harmful? A review of the evidence

OBJECTIVE

To consider whether consumption of black tea has a positive or negative impact on health.

DESIGN

Databases were searched for relevant epidemiological and clinical studies published between 1990 and 2004.

RESULTS

Clear evidence was found for coronary heart disease (CHD), where an intake of > or = 3 cups per day related to risk reduction. The mechanism could involve the antioxidant action of tea polyphenols. While experimental models have suggested that flavonoids attenuated cancer risk, epidemiological studies failed to demonstrate a clear effect for tea, although there is moderate evidence for a slightly positive or no effect of black tea consumption on colorectal cancer. Studies on cancer were limited by sample sizes and insufficient control of confounders. There is moderate evidence suggestive of a positive effect of black tea consumption on bone mineral density although studies were few. There is little evidence to support the effect of tea on dental plaque inhibition but evidence to support the contribution of tea to fluoride intakes and thus theoretical protection against caries. There was no credible evidence that black tea (in amounts typically consumed) was harmful. Normal hydration was consistent with tea consumption when the caffeine content was < 250 mg per cup. A moderate caffeine intake from tea appeared to improve mental performance, although sample sizes were small. There was no evidence that iron status could be harmed by tea drinking unless populations were already at risk from anaemia.

CONCLUSIONS

There was sufficient evidence to show risk reduction for CHD at intakes of > or = 3 cups per day and for improved antioxidant status at intakes of one to six cups per day. A maximum intake of eight cups per day would minimise any risk relating to excess caffeine consumption. Black tea generally had a positive effect on health.

Green tea, black tea and colorectal cancer risk: a meta-analysis of epidemiologic studies

Experimental studies have supported tea as a chemopreventive agent for colorectal cancer. No quantitative summary of the epidemiologic evidence on tea and colorectal cancer risk has ever been performed. The current meta-analysis included 25 papers conducted in 11 countries across three continents (North America, Asia and Europe). Summary odds ratios (ORs) for highest versus non/lowest tea consumption levels were calculated based on fixed and random effects models. The meta-regression and stratified methods were used to examine heterogeneity across studies. For green tea, the combined results from eight studies indicated a reduced risk of colorectal cancer with intake [summary OR = 0.82, 95% confidence interval (CI) = 0.69-0.98]. The protective effect is mainly found among the three case-control studies of colon cancer (summary OR = 0.74, 95% CI = 0.60-0.93). Results from studies of rectal cancer irrespective of study design (case-control versus cohort) (summary OR = 0.99, 95% CI = 0.71-1.37) and cohort studies of colon cancer (summary OR = 0.99, 95% CI = 0.79-1.24) were compatible with the null hypothesis. For black tea, the summary OR derived from 20 studies was 0.99 (95% CI = 0.87-1.13). There is wide divergence in results across the 20 individual studies; formal tests for homogeneity across studies revealed statistically significant differences in findings across all studies (P < 0.001), amongst the 7 cohort studies (P = 0.002), and amongst the 13 case-control studies (P < 0.001). Despite the strong evidence from in vitro and non-human in vivo studies in support of green and black tea as potential chemopreventive agents against colorectal cancer, available epidemiologic data are insufficient to conclude that either tea type may protect against colorectal cancer in humans.

Intakes of selected food groups and beverages and adult acute myeloid leukemia

Few studies have explored the association between diet and adult acute myeloid leukemia (AML). In a hospital-based case-control study among 111 cases and 439 controls, AML risk was negatively associated with milk intake among women (OR 0.25, 95% CI 0.08-0.73) and tea (OR 0.50, 95% CI 0.23-1.09), and positively associated among women with beer (OR 2.48, 95% CI 1.05-5.85), wine (OR 2.32, 95% CI 1.05-5.09), and beef (OR 4.78, 95% CI 1.35-16.94). Our findings support a role of diet in adult AML; however, further research is needed to explore gender differences in risk.

Relative and absolute risk of colorectal cancer for individuals with a family history: A meta-analysis

Accurate risk estimates for individuals with a family history of colorectal cancer are important for surveillance strategies. We systematically reviewed the literature on familial risks of colorectal cancer to determine relative risk estimates for categories of family history and translated these relative risk estimates into absolute risk estimates. A random-effects meta-analysis pooled the effect estimates from individual studies and actuarial life-table methods converted relative into absolute risks. Fifty-nine studies were identified including 47 that estimated the relative risk of developing colorectal cancer given at least one affected first-degree relative. The pooled risk estimate was 2.24 (95% CI 2.06 to 2.43) which rose to 3.97 (95% CI 2.60 to 6.06) with at least two affected relatives. A population lifetime risk of 1.8% for a 50-year old increased to 3.4% (95% CI 2.8 to 4.0) with at least one affected relative or 6.9% (95% CI 4.5 to 10.4) with two or more. Accurate absolute risk estimates show how cancer risks vary over time, particularly by pattern of family history and age of individual at-risk.

Pharmacological effects of green tea on the gastrointestinal system

Green tea is rich in polyphenolic compounds, with catechins as its major component. Studies have shown that catechins possess diverse pharmacological properties that include anti-oxidative, anti-inflammatory, anti-carcinogenic, anti-arteriosclerotic and anti-bacterial effects. In the gastrointestinal tract, green tea was found to activate intracellular antioxidants, inhibit procarcinogen formation, suppress angiogenesis and cancer cell proliferation. Studies on the preventive effect of green tea in esophageal cancer have produced inconsistent results; however, inverse relationships of tea consumption with cancers of the stomach and colon have been widely reported. Green tea is effective to prevent dental caries and reduce cholesterols and lipids absorption in the gastrointestinal tract, thus benefits subjects with cardiovascular disorders. As tea catechins are well absorbed in the gastrointestinal tract and they interact synergistically in their disease-modifying actions, thus drinking unfractionated green tea is the most simple and beneficial way to prevent gastrointestinal disorders.

Choice of exposure scores for categorical regression in meta-analysis: a case study of a common problem

OBJECTIVE

Reporting categorical relative risk estimates for a series of exposure levels versus a common reference category is a widespread practice. In meta-analysis, categorical regression estimates a dose-response trend from such results. This method requires the assignment of a single score to each exposure category. We examined how closely meta-analytical categorical regression approximates the results of analysis based on the individual-level continuous exposure.

METHODS

The analysis included five studies on tea intake and outcomes related to colorectal cancer. In addition, we derived categorical mean and median values from published distributions of tea consumption in similar populations to assign scores to the categories of tea intake when possible. We examined whether these derived mean and median values well approximate the individual-level results.

RESULTS

In meta-analytical categorical regression, using the midrange scores approximated the individual-level continuous analyses reasonably well, if the value assigned to the uppermost, open-ended category was at least as high as the lower bound plus the width of the second-highest category. Categorical mean values derived from the published distributions of regular tea (in the US) and green tea (in Japan) well approximated the slope obtained from individual-level analysis.

CONCLUSION

Publication of both the categorical and the continuous estimates of effect in primary studies, with their standard errors, can enhance the quality of meta-analysis, as well as providing intrinsically valuable information on dose-response.

Daily tea drinking is associated with a low level of depressive symptoms in the Finnish general population

Tea drinking has been suggested to be beneficial in neurodegenerative diseases where depressive mood is a common symptom. Nevertheless, it is not known whether there are any associations between tea drinking and depression in general populations. In this study we investigated these associations in a sample of the Finnish general population (n = 2011) using a postal questionnaire and the Beck Depression Inventory (BDI). Those who reported drinking tea daily were less depressed than the others. They had a lower mean BDI score and also a lower prevalence of depression. None of those whose daily tea intake was five cups or more had depression. Several potential confounding factors were included in the final sex- and age-adjusted multivariate logistic regression model which suggested that those who drink tea daily may have a significantly reduced risk of being depressed (adjusted odds ratio 0.47, 95% confidence interval 0.27-0.83). In conclusion, an inverse relationship between daily tea drinking and the risk of being depressed was found in a relatively large general population sample. Nevertheless, the underlying mechanisms are unresolved and further studies are needed.

Association of Fluids From Beverages With Risk of Rectal Cancer

Little information is available about how fluid intake from beverages and sources of fluid intake influence risk of rectal cancer. We examined these associations with risk of incident rectal cancer in a population-based case-control study of 952 cases and 1,205 controls living in northern California and Utah. We also determined if intake of fiber (soluble and insoluble), physical activity, and nonsteroidal anti-inflammatory medications (NSAIDs) or aspirin modified the associations between fluid intake and rectal cancer. We identified a modest inverse association of water intake (odds ratio, OR = 0.70; 95% confidence interval, CI = 0.48, 1.02) and total fluid intake (high vs. low OR = 0.70; 95% CI = 0.46, 1.06) with risk of rectal cancer in men and a positive association with juice among women (high vs. low OR = 1.56; 95% CI = 1.00, 2.41). Risk of rectal cancer increased nonsignificantly among men with beer consumption, among women with high white wine use, and among men and women with high long-term alcohol use. NSAIDs modified the association of alcohol consumption with rectal cancer: 1) risk associated with beer increased among men who did not take NSAIDs and had a high beer intake (OR = 1.60; 95% CI = 1.08, 2.39) and 2) risk associated with long-term alcohol intake increased in a linear fashion in women who did not use NSAIDs (OR = 1.98; 95% CI = 1.15, 3.40). Risk of rectal cancer increased among estrogen-negative women if they consumed any beer or white wine but decreased among estrogen-positive women with beer. In men, low intake of water and low insoluble fiber intake were associated with increased risk of rectal cancer beyond that of either factor alone (OR = 1.82; 95% CI = 1.11, 3.00). The interactions of fiber with water intake suggest that bowel motility may be the mechanism responsible for modification of rectal cancer risk for water. Associations of alcohol to risk for rectal cancer may be related to cellular hyperproliferation and may be modified by NSAID use.

The epidemiology of tea consumption and colorectal cancer incidence

This manuscript provides a brief synopsis of 30 studies aimed at examining tea consumption as a factor in the incidence of colon and rectal cancers. The 30 papers examine populations in 12 countries and provide data on consumption of both black and green tea. These studies do not provide consistent evidence to support the theory from animal studies and basic research that tea is a potent chemopreventive agent. Details of the studies are presented, and the potential impact of measurement error, publication bias, the form of tea consumed, the appropriateness of the outcomes studied and the adjustment of confounders related to both tea consumption and risk of colorectal cancer or polyps in various countries are explored. In general, the data are not more consistent for green than for black tea. Particularly with green tea, the doses consumed do get into a perceived protective range in a significant subset of the population. A negative association is stronger in observational epidemiologic studies of rectal cancer than in colon cancer. There is no consistent adjustment for important potential confounders of any tea relationship, such as coffee and alcohol consumption and physical activity levels. Finally, the assessment of tea in most of these studies was based on a single question and therefore may have significant measurement error compared with more recent studies specifically aimed at assessing tea consumption.

Tea consumption, apoptosis, and colorectal adenomas

Induction of apoptosis has been suggested as a mechanism for the anti-carcinogenic effect of tea constituents in animals and in vitro studies. We addressed this hypothesis in a human study. Study participants were consecutive patients who underwent colonoscopy at the UNC Hospitals (August 1998 to March 2000). Biopsies were taken from normal rectal mucosa. Apoptosis was scored by the terminal deoxyribonucleotide transferase-mediated digoxigenin dUTP nick end labeling (TUNEL) method and by standard morphological criteria. The analysis included 171 patients with adenomas (cases) and 323 adenoma-free controls. After adjusting for sex, age, race, and BMI, apoptotic score was inversely associated with adenoma: the odds ratios (ORs) for linear trend associated with tertiles were 0.3 (0.3-0.5) for morphologic score and 0.5 (0.4-0.6) for the TUNEL score, respectively. Tea consumption (2-3 and >3 versus <2 servings/day) showed a weak negative association with adenoma: the ORs were 0.7 (0.3-1.4) and 0.5 (0.2-1.1), respectively. Neither measurement of apoptotic score changed by the level of tea consumption (P value for Kruskal-Wallis test > or =0.5). We did not find statistical interaction between apoptotic score and tea consumption. Tea exposure is not associated with apoptosis in normal rectal tissue in vivo.