Long-term Tea Consumption Research Articles

Accumulation of potentially toxic elements in Chinese tea (Camellia sinensis): Towards source apportionment and health risk assessment

Tea (Camellia sinensis) is a popular beverage that is consumed globally. However, a better understanding of potentially toxic elements (PTEs) content in tea leaves and infusion is necessary to minimize risk on human health. Therefore, 249 tea samples (grown in different areas) covering six types of tea were collected in China to investigate the PTEs contents, identify their potential source and assess the health risk associated with drinking tea. PTE contents in tea leaves across six tea types were ND–0.900 (Cd), 0.005–2.133 (As), ND–5.679 (Pb), ND–13.86 (Cr), 1.601–22.93 (Ni), ND–2.048 (Se), 0.109–622.4 (F), 13.02–269.9 (Rb), 1.845–50.88 (Sr), and 2.796–53.23 (Ba) mg/kg. The result of tea infusion showed that 14.3 %–44.1 % (green tea), 14.5 %–46.7 % (black tea), 10.5 %–25.3 % (dark tea), 13.6 %–34.2 % (oolong tea), 16.9 %–40.7 % (yellow tea), and 19.9 %–35.1 % (white tea) of F were released. All tea types, except green tea, exhibited comparatively low leachability of Cd, As, Pb and Cr in tea infusion. The source apportionment revealed that PTEs in tea leaves mainly originated from soil parental materials, while industrial activities, fertilizer application, and manufacturing processes may contribute to exogenous Se, Cd, As, and Cr accumulation. Health risk assessment indicated that F in tea infusion dominated the health risk. Humans may be exposed to a higher health risk by drinking green tea compared to that of other tea types. Nevertheless, the long-term tea consumption is less likely to contribute to pronounced non-carcinogenic and carcinogenic risks. This study confirmed that tea consumption is an important and direct pathway of PTEs uptake in humans. The health risk associated with drinking tea should be of concern.

Long-term tea consumption reduces the risk of frailty in older Chinese people: Result from a 6-year longitudinal study.

BackgroundVast accumulative evidence suggests that the consumption of tea and its components have various potential health benefits. This study used a longitudinal study to examine the causality between tea consumption and frailty in older Chinese people.MethodsThis study employed the longitudinal data from 2008 to 2014 of the Chinese Longitudinal Healthy Longevity Survey (CLHLS), which were systematically collected through face-to-face interviews. Two thousand four hundred and seventy three participants completed six-follow-up surveys in 2014 and were analyzed in this study. The frailty index recommended by Searle and co-authors, including 44 health deficits, was used. A Generalized Estimating Equation (GEE) was applied to determine the risk ratio (RR) with a 95% confidence interval (CI) for frailty, and further subgroup analyses were conducted to investigate whether the risk differed stratified by age, sex, and socioeconomic status. Additionally, the interaction between tea consumption with sex and frailty was tested.ResultsOf the 2,473 participants, 14.1% were consistent daily tea drinkers, and 22.6% reported frailty at the 6-year follow-up. Compared to non-tea drinkers, consistent daily tea drinkers reported a significantly lower ratio of having frailty [risk ratio (RR) = 0.54, 95% confidence interval (CI): 0.38–0.78], adjusting for sociodemographic characteristics, health behavior, socioeconomic status, and chronic illnesses. In further subgroup analyses, consistent daily tea consumption significantly reduced the risk of frailty for males (RR = 0.53, 95% CI: 0.32–0.87) but not females (RR = 0.65, 95% CI: 0.37–1.12); in the young (RR = 0.40, 95% CI: 0.22–0.74) but not in the oldest (aged ≥ 80) (RR = 0.66, 95% CI: 0.40–1.06); informal education (RR = 0.48, 95% CI: 0.28–0.84) but not formal education (RR = 0.62, 95% CI: 0.37–1.03); financial dependence (RR = 0.42, 95% CI: 0.25–0.71) but not financial independence (RR = 0.71, 95% CI: 0.41–1.23). Additionally, females showed a lower tea-mediated risk of frailty in occasional tea consumers (RR = 0.51, 95% CI: 0.29–0.89) and inconsistent tea drinkers (RR = 0.58, 95% CI: 0.37–0.93).ConclusionsHabitual tea consumption can reduce the risk of frailty in older Chinese, and the benefit varied by age, sex, education, and financial support.

Long-Term Tea Consumption Is Associated with Reduced Risk of Diabetic Retinopathy: A Cross-Sectional Survey among Elderly Chinese from Rural Communities.

Aim To investigate the association between variables related to tea consumption (duration, frequency, and type) and the risk of diabetic retinopathy. Methods A rural community-based, cross-sectional survey was conducted in Weitang Town, Suzhou, China. People aged 60 years or above were invited to complete the survey. All eligible patients underwent detailed eye examination. Diabetic retinopathy (DR) was diagnosed and graded based on the retinal fundus imaging. Diabetes was defined as fasting glucose concentrations of ≥7.0 mmol/L or self-reported diagnosis of diabetes. Information about tea consumption such as duration, type, and frequency, together with demographics and lifestyle characteristics, were collected using a face-to-face questionnaire interview. The association between tea consumption and the risk of DR was determined by univariate and multivariate logistic regression analyses. Results Among the 5,281 participants, 614 had diabetes mellitus (prevalence of 11.63%). The prevalence rate of DR was 10.38% in the diabetic population and 1.04% in the general population. Compared with non-tea consumers, the crude OR values for DR in subjects with long-term and short-term tea consumption were 0.34 (95%CI = 0.14‐0.82, p = 0.016) and 1.64 (95%CI = 0.74‐3.64, p = 0.221), respectively. When adjusted for age, gender, and other confounders, consumption of tea for ≥20 years was associated with reduced odds of DR (OR = 0.29, 95%CI = 0.09‐0.97, p = 0.044). Thus, long-term tea consumption was significantly associated with a lower risk of DR. There was no statistical significance between frequency or type of tea consumption with DR (p > 0.05). Conclusion Elderly diabetic Chinese residents who consumed tea for more than twenty years had a lower risk of DR compared to non-tea consumers. The long-term tea consumption may be an independent protective factor for DR. However, further studies are warranted to examine the association.

Letter to the editor: Long-Term Tea Consumption and Depressive and Anxiety Symptoms in Elderly.

To the editor, the publication on “Associations of Long-Term Tea Consumption with Depressive and Anxiety Symptoms in Community-Living Elderly” is very interesting (1). Chan et al. concluded that “There was evidence suggesting that long-term tea consumption was associated with reduced depressive and anxiety symptoms among community-living elderly (1).” In fact, tea drinking is a rooted behavior among Chinese Asian population. The health usefulness of tea is approved. Neuroprotective system due to tea drinking is believed to due to the active ingredients including to flavonoids (2). In a recent report, the green tea was found to have more neuroprotective activity than red and black tea (3). It is no doubt that the long-term tea consumption can result in neuroprotective effect as reported by Chan et al (1). However, as noted by Chan, further investigation is needed. The main concern for the present report is confounding effect that is not controllable. The studied elderly might have other foods, beverages or activities that can help protect against depressive and anxiety symptoms. Finally, tea contain caffeine, an extremely high dose drinking might result in problem, induction of anxiety instead of prevention of anxiety (4).

Letter to the editor: Responses. Long-Term Tea Consumption and Depressive and Anxiety Symptoms in Elderly.

Responses: We thank Dr Joob and Dr Wiwanitkit for their interest in our research work and the valuable comments and suggestions they have provided. I fully agree with them that some uncontrolled factors, such as the intake of other foods, beverages or activities, may help protect against depressive and anxiety symptoms, and hence residual confounding cannot be completely ruled out. Further investigation is needed for a definitive conclusion. Indeed, motivated by growing evidence on neuroprotective benefits of tea consumption (1), my coworkers and I are now planning a new study in which we aim to assess the effects of tea drinking on brain health in a randomized controlled trial.

Associations of Long-Term Tea Consumption with Depressive and Anxiety Symptoms in Community-Living Elderly: Findings from the Diet and Healthy Aging Study.

To examine the association between long-term tea consumption and depressive and anxiety symptoms in community-living elderly. Community based cross-sectional study. The Diet and Healthy Aging Study (DaHA), a prospective cohort study in Singapore. 614 elderly aged 60 years and above, who were free of dementia and cognitive impairment. Information on tea consumption was obtained through interviewer-administered questionnaire. Long-term tea drinking was defined as regular consumption for at least 15 years. Depressive and anxiety symptoms were measured using the 15-item Geriatric Depression Scale (GDS-15) and the 20-item Geriatric Anxiety Inventory (GAI), respectively. A generalized structural equation model (gSEM) was applied to ascertain the association between long-term tea consumption and depressive and anxiety symptoms. About 59% of the subjects had consumed tea for over 15 years. Long term tea consumption was significantly associated with a reduced odds of having depressive and anxiety symptoms, after adjusting for demographics (i.e., age, gender, education and ethnicity), comorbid conditions (i.e., heart disease, diabetes, stroke, hypertension and hyperlipidaemia) and long-term coffee consumption. There was evidence suggesting that long-term tea consumption was associated with reduced depressive and anxiety symptoms among community-living elderly. This suggests that it is worthwhile to further investigate the role of tea's bioactive compounds in promoting mental health in aging.

Pu-erh tea attenuates smoking-induced foam cell formation through inhibition of the α9-nicotinic-acetylcholine receptor expression in monocytes: An ex vivo study

To assess whether drinking tea can effectively prevent smoking-induced atherosclerosis, a clinical trial ex vivo study was performed. The volunteers were randomly allocated to two groups (n = 55 per group) that received either Pu-erh tea powder or a cellulose placebo (0.5 g/capsule, T.I.D.) for two months. The circulating monocytes were isolated from the tested individuals after 0, 1, and 2 months of tea-capsule administration. We found that monocytes displaying high α9-nicotinic-acetylcholine-receptor (α9-nAchR) expression that were isolated from heavy smokers before consuming tea capsules tended to form foam cells in response to nicotine (1 µL for 24 h, *P < 0.001). In contrast, long-term tea consumption significantly downregulated the monocytic α9-nAchR expression (0 months vs. 1 and 2 months; #P = 0.013 and ##P = 0.004, respectively) which causes circulating monocytes to resist nicotine-induced foam cell formation even in heavy-smokers (*P < 0.001). This study suggests that tea-drinking effectively attenuates the initial step (foam-cell formation) of smoking-induced atherosclerosis in circulating monocytes.

Tea Consumption and Ischemic Stroke Risk

Although experimental studies have suggested that tea consumption may reduce the risk of ischemic stroke, available epidemiological evidence is equivocal, mainly due to the lack of accurate measurements on tea exposure. This study aims to ascertain the relationship between tea drinking and ischemic stroke risk. A case-control study was conducted in southern China from 2007 to 2008. A total of 374 patients with incident ischemic stroke and 464 control subjects (mean age, 69 years) were recruited from 3 hospitals in Foshan. Information on frequency and duration of tea drinking, quantity of dried tea leaves, and types of tea consumed, together with habitual diet and lifestyle characteristics, was obtained from participants using a validated and reliable questionnaire. Logistic regression analyses were performed for tea consumption variables accounting for confounders that affect the ischemic stroke risk. A significant decrease in ischemic stroke risk was observed for drinking at least one cup of tea weekly (P=0.015) when compared with infrequent or nondrinkers, the risk reduction being largest by drinking one to 2 cups of green or oolong tea daily. Significant inverse dose-response relationships were also found for years of drinking and the amount of dried tea leaves brewed. The adjusted ORs for the highest level of consumption in terms of frequency of intake, duration of drinking, and average tea leaves brewed were 0.61 (95% CI, 0.40 to 0.94), 0.40 (95% CI, 0.25 to 0.64), and 0.27 (95% CI, 0.16 to 0.46), respectively. Long-term tea consumption is associated with reduced risk of ischemic stroke.