Association between tea, coffee and caffeine consumption and risk of female infertility: a cross-sectional study.

OBJECTIVES: To explore the association between tea, coffee, and caffeine consumption and the risk of female infertility. METHODS: We analyzed data from 2099 females aged 18 to 44 years, participating in the National Health and Nutrition Examination Survey (NHANES) 2013-2018. We used generalized linear models (GLM) and generalized additive model (GAM) to investigate the dose-response relationship between the tea, coffee, and caffeine consumption and infertility, adjusting for potential confounders. RESULTS: A non-linear relationship was detected between tea consumption and infertility and the inflection point was 2 cups/day. On the right side of the inflection point, we did not detect a significant association. However, on the left side, we found a negative relationship between tea consumption and infertility (OR: 0.73; 95% CI: 0.57 to 0.93; P = 0.0122). Meanwhile, our study found no significant association between coffee (0.96, 0.81 to 1.13, P = 0.6189) or caffeine consumption (1.15, 0.93 to 1.42, P = 0.2148) and female infertility. CONCLUSIONS: Tea consumption was non-linearly associated with infertility, whereas no significant associations were found between coffee, caffeine consumption and infertility.

Relationship between sex differences in drinking, smoking, and exercising and the incidence of malignancies and medical procedures: a cross-sectional study of 21,916 participants in China.

Objectives: The unresolved issue of the relationship between sex differences in tea, coffee, and beverage consumption and malignancy risk prompted our study in 2022. Methods: Logistic proportional hazards models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) in our investigation of the associations between cancer risk and tea, coffee, and beverage consumption. Results: Our findings revealed that frequent consumption of white tea significantly reduced the occurrence of malignant tumours, but this effect was detected only in the fully adjusted model for males (OR: 0.736, 95% CI: 0.095-5.704). The amount of sugar added to coffee was associated with an increased risk of malignancy in a dose-dependent manner (P for trend = 0.001), with significance observed for both men (P for trend = 0.049) and women (P for trend = 0.005) in the final model. Notably, individuals who consumed more than 2100 ml of sugary beverages daily had a statistically significant reduction in malignancy risk (OR: 0.219, 95% CI: 0.052-0.917). Interestingly, the intake of sugary beverages had a protective effect on cancer incidence, with a significant effect on males (P for trend = 0.031) but not females (P for trend = 0.096) in the final model. Conclusions: Our study highlights the substantial impact of regular white tea consumption on reducing the risk of malignant tumours in males. This study first reported that the potential protective effect of consuming sugary beverages is predominantly observed in males, and a correlation between the amount of sugar added to coffee and a heightened risk of malignancy.

Association of coffee and tea consumption with osteoporosis risk: A prospective study from the UK biobank.

OBJECTIVE: The association of coffee and tea consumption with osteoporosis is highly controversial, and few studies have focused on the combined effects of the two beverages. This study aimed to investigate the independent and combined associations of coffee and tea consumption with osteoporosis risk. METHODS: A prospective cohort study involving 487,594 participants aged 38-73 years from the UK Biobank was conducted. Participants with reported coffee and tea consumption and without osteoporosis at baseline were included. Coffee and tea consumption were assessed via a touch-screen questionnaire at baseline. Newly diagnosed osteoporosis during the follow-up period, defined based on ICD-10 codes (M80-M82), was the primary outcome. Cox regression analyses were utilized to calculate hazard ratios (HRs) and 95 % confidence intervals (CIs). Dose-effect associations were assessed using restricted cubic spline analysis. RESULTS: During a median follow-up of 12.8 years, 15,211 cases of osteoporosis were identified. Compared to individuals without coffee or tea consumption, drinking coffee was associated with an HR of 0.93 (95 % CI: 0.89-0.96), and tea consumption with an HR of 0.86 (95 % CI: 0.83-0.90). Continuous trends were significant for both coffee and tea consumption, showing non-linear associations with osteoporosis incidence. Moderate consumption, such as 1-2 cups of coffee or 3-4 cups of tea per day, was associated with a lower incidence of osteoporosis, with HRs of 0.9 (95 % CI: 0.86-0.94) and 0.85 (95 % CI: 0.81-0.90), respectively. Additionally, combined coffee and tea consumption displayed a U-shaped association with osteoporosis risk, with the lowest risk observed in individuals who consumed 1-2 cups of both beverages daily, with an HR of 0.68 (95 % CI: 0.61-0.75). CONCLUSION: Our findings highlight the potential benefits of moderate coffee and tea consumption in reducing the risk of osteoporosis.

Investigating the Impact of Tea Consumption on Cognitive Function and Exploring Tea-Genetic Interactions in Older Adults Aged 65-105 Years: Findings from the 2002-2018 CLHLS Data.

BACKGROUND: As the global population ages, cognitive impairment (CI) becomes more prevalent. Tea has been one of the most popular drinks in the world. Several studies have demonstrated that tea consumption has an impact on cognitive function. OBJECTIVE: This study aims to examine the association between tea consumption and cognitive function and explore the potential effect of genetics on the relationship between tea consumption and CI risk in older adults. DESIGN: This is a prospective longitudinal study using data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). SETTING: Six waves of data from CLHLS containing 76,270 subjects were analyzed. Generalized estimation equations (GEE) with a logit link function were adopted to estimate the effect of tea consumption on CI risk from a cross-sectional and longitudinal perspective. PARTICIPANTS: A population-based cohort of adults aged 65-105 years. MEASUREMENTS: The frequency and type of tea consumption were obtained by questionnaires. CI was measured based on MMSE. Polygenic risk was measured using the polygenic score approach described by the International Schizophrenia. RESULTS: The results showed that drinking green tea had a better protective effect on cognitive function than other types of tea, the incidence of CI gradually decreased with the increase of tea consumption frequency, and men were more likely to benefit from tea consumption. Additionally, we also found a significant interaction between tea consumption and genetic risk, measured by polygenic risk score (PRS). CONCLUSIONS: Based on current research evidence, tea consumption, may be a simple and important measure for CI prevention.

Coffee and green tea consumption with the risk of COVID-19 among the vaccine recipients in Japan: a prospective study.

BACKGROUND: While coffee and green tea have been suggested to have immunoprotective effects, it remains elusive whether they can decrease the risk of COVID-19. OBJECTIVE: We prospectively examined the association between coffee and green tea consumption and the risk of COVID-19 among mRNA vaccine recipients during the epidemic of the Omicron variant. METHOD: Participants were 2,110 staff (aged 18 to 76 years) of a large medical facility in Tokyo, who attended a serosurvey in June 2022, predominatly received ≥3 doses of vaccine, and were followed for COVID-19 until December 2022. Coffee and green tea consumption was ascertained via a questionnaire. COVID-19 was identified through the in-house registry. Cox proportional hazards model was used to estimate the hazard ratios (HRs) of COVID-19 across the categories of beverage consumption. RESULT: During 6 months of follow-up, 225 (10.6%) cases of COVID-19 were identified. Contrary to the expectation, higher consumption of coffee was associated with a significant increase in the risk of COVID-19; multivariable-adjusted HRs (95% CI) was 1.00, 0.92 (0.62-1.35), 1.48 (0.99-2.22), and 1.82 (1.20-2.76) for <1 cup/day, 1 cup/day, 2 cups/day, and ≥3 cups/day, respectively (p trend=0.003). Green tea consumption was not significantly associated with the risk of COVID-19. The association with coffee was attenuated if serologically detected infection was added to the cases. CONCLUSION: In a cohort of Japanese hospital staff who received COVID-19 vaccine, higher consumption of coffee was associated with an increased risk of COVID-19 during the epidemic of the Omicron variant. There was no evidence of a significant association between green tea consumption and COVID-19 risk.

Association between tea consumption and risk of kidney stones: results from dose-response meta-analysis of prospective studies and Mendelian randomization analysis.

PURPOSE: The association between tea consumption and kidney stones is inconsistent in observational studies. Thus, we performed a dose-response meta-analysis of prospective cohort studies and a two-sample Mendelian randomization (MR) analysis to identify this association. METHODS: The prospective cohort studies reporting the relationship between tea consumption and kidney stones were searched from PubMed, the Cochrane Library, EMBASE, and Web of Science from inception to December 1, 2023. For MR analysis, the summary-level data for tea consumption and kidney stones were extracted from the UK Biobank available data and the 8th release of the FinnGen consortium, respectively. The inverse-variance weighted (IVW) method was the primary analytical method. RESULTS: In our dose-response meta-analysis, four prospective cohort studies involving 1,263,008 participants were included, and tea consumption was found to have significant associations with kidney stones (RR: 0.80, 95% CI: 0.73-0.87). We also observed a substantially linear negative relationship between tea consumption and the risk of kidney stones. In MR analysis, the IVW method indicated that tea consumption was inversely associated with kidney stones (OR: 0.71, 95% CI: 0.53-0.94). CONCLUSION: Our study confirmed a causal relationship between tea consumption and kidney stones, and higher tea consumption may reduce the risk of kidney stones.

Consumption Pattern of Tea Is Associated with Serum Ferritin Levels of Women of Childbearing Age in Nandi County, Kenya: A Cross-Sectional Study.

INTRODUCTION: Tea consumption with meals affects iron absorption, increasing the risk of iron deficiency. Our study investigated the association between tea consumption patterns and serum ferritin levels among women of childbearing age (WCA) in Nandi County, Kenya. METHODS: We conducted a cross-sectional analytical study among 160 WCA selected using a systematic random sampling technique from Kapsabet Ward. Information on tea consumption practices was gathered using a researcher-administered questionnaire, and serum ferritin and C-reactive protein were measured. We assessed associations between tea consumption and iron status of respondents by multivariable regression analysis, adjusting for potential confounders, including parasitic infections and recent severe blood losses. RESULTS: The prevalence of anaemia and iron deficiency among the study participants were 86.2% and 45%, respectively. Majority (90.6%) of the respondents consumed tea or coffee, with an infusion time of more than 5 min (60.0%) and a moderate tea strength (64.1%), within 1 h before or after meals. Iron deficiency was associated the number of teacups consumed (adjusted odds ratio = 7.282, 95% CI = 3.580-14.812). CONCLUSION: High tea consumption is positively associated with iron deficiency among WCA. Lower tea infusion strength, shorter tea infusion duration, and a lower number of teacups overall consumed, as well as consuming tea 1 h before or after meals instead of with meals, may be recommended for better outcomes in iron status among WCA.

The Association Between Habitual Tea Consumption and Frailty Transition in Community-Dwelling Older Adults: A Prospective Cohort Study.

OBJECTIVES: To investigate the association between habitual tea consumption and transitions between frailty states among older adults in China. DESIGN: A prospective cohort study based on the Chinese Longitudinal Healthy Longevity Study. SETTING AND PARTICIPANTS: A total of 23,720 older adults aged ≥65 years with complete data regarding frailty status and tea consumption were recruited. METHODS: The frequency and consistency of tea consumption were introduced to evaluate levels of tea consumption. The frailty index was used to define frailty status (frail and nonfrail). Frailty transition was classified into remaining nonfrail, improvement, worsening, and remaining frail groups. Logistic regression models were applied. RESULTS: The overall frailty prevalence at baseline was 19.1%, being lower among consistent daily tea drinkers (12.5%) and higher among non-tea drinkers (21.9%). Logistic regression analyses showed that the risk of frailty was significantly reduced among consistent daily tea drinkers after adjusting for all confounders [odds ratio (OR), 0.81; 95% CI, 0.67-0.98]. During the 3-year follow-up, improvement in frailty status was more common among consistent daily tea drinkers (50.9%) than non-tea drinkers (40.9%), and this trend was opposite in participants with worsened frailty status (consistent daily tea drinkers: 12.2%) vs non-tea drinkers: 19.2%). Further analysis showed that consistent daily tea drinkers were significantly associated with improvement in frailty status (OR, 3.24; 95% CI, 1.02-10.31) and remaining in a nonfrail state (OR, 1.35; 95% CI, 1.00-1.83). In addition, daily tea consumption was observed to be positively associated with remaining in a nonfrail state and inversely associated with worsened frailty status in men, but not in women. CONCLUSIONS AND IMPLICATIONS: Older people consuming tea daily tend to have an improved frailty status in the future. Men with daily tea consumption were less likely to have a worsened frailty status. Advocating for the traditional lifestyle of drinking tea could be a promising way to advance healthy aging for older adults.

Tea consumption and risk of bone health: an updated systematic review and meta-analysis.

INTRODUCTION: Current research evaluating the association between tea consumption and bone health still has inconsistent findings. MATERIALS AND METHODS: The electronic databases of Embase, PubMed, Scopus, and Web of Science were systematically searched from inception until December 2022 to identify eligible studies. The calculation of summary relative risks (RRs) and 95% confidence intervals (CIs) was carried out using random-effects models. I2 statistics and Forest plots were used to assess the heterogeneity of RR values across studies. RESULTS: The pooled relative risks for bone health-related outcomes of interest among tea drinkers, compared to non-drinkers, were 0.910 (95% confidence interval 0.845 to 0.980) for fractures, based on 20 studies, 0.332 (0.207-0.457) for BMD (13 studies), 0.800 (0.674-0.950) for osteoporosis (10 studies), and 1.006 (0.876-1.156) for osteopenia (5 studies). Subgroup analysis of locations showed that the pooled relative risks were 0.903 (0.844-0.966) for the hip, 0.735 (0.586-0.922) for the femur, 0.776 (0.610-0.988) for the lumbar, 0.980 (0.942-1.021) for the forearm and wrist, 0.804 (0.567-1.139) for the phalanges, and 0.612 (0.468-0.800) for Ward's triangle. One-stage dose-response analysis revealed that individuals who consumed less than 4.5 cups of tea per day had a lower risk of bone health-related outcomes than those who did not consume tea, with statistically significant results. CONCLUSION: There is an association between tea consumption and a reduced risk of fractures, osteoporosis, hip, femur, and lumbar, as well as increased BMD.

Tea consumption and attenuation of biological aging: a longitudinal analysis from two cohort studies.

Background: The biological aging process can be modified through lifestyle interventions to prevent age-related diseases and extend healthspan. However, evidence from population-based studies on whether tea consumption could delay the biological aging process in humans remains limited. Methods: This study included 7931 participants aged 30-79 years from the China Multi-Ethnic Cohort (CMEC) Study and 5998 participants aged 37-73 years from the UK Biobank (UKB) who participated in both the baseline and first follow-up surveys. Tea consumption information was collected through questionnaires. Biological age (BA) acceleration was calculated using clinical biomarkers and anthropometric measurements based on the Klemera Doubal method (KDM). Change-to-change analyses were performed to estimate the associations between changes in tea consumption status and changes in BA acceleration using multiple linear models. Follow-up adjusted for baseline analyses were further conducted to examine the prospective exposure-response relationship between tea consumption and BA acceleration among individuals with constant tea consumption status. Findings: During a median follow-up of 1.98 (1.78, 2.16) years in the CMEC and 4.50 (3.92, 5.00) years in the UKB, tea consumption was consistently associated with attenuated BA acceleration in both cohorts. Transitioning from nondrinking to tea-drinking was associated with decreased BA acceleration (CMEC: ß = -0.319, 95% CI: -0.620 to -0.017 years; UKB: ß = -0.267, 95% CI: -0.831 to 0.297 years) compared to consistent nondrinking. Even stronger associations were found in consistent tea drinkers. The exposure-response relationship suggested that consuming around 3 cups of tea or 6-8 g of tea leaves per day may offer the most evident anti-aging benefits. Interpretation: Tea consumption was associated with attenuated BA acceleration measured by KDM, especially for consistent tea drinkers with moderate consumption. Our findings highlight the potential role of tea in developing nutrition-oriented anti-aging interventions and guiding healthy aging policies. Funding: National Natural Science Foundation of China (Grant No. 82273740).

Tea consumption and risk of lung diseases: a two­sample Mendelian randomization study.

BACKGROUND: Numerous studies have reported the association between tea intake and lung diseases. However, the probable relationship between tea consumption on lung diseases still remain controversial and it is unclear whether these findings are due to reverse causality or confounding factor. METHODS: In order to systematically investigate the causal connection between tea intake on respiratory system disorders, we employed a two-sample Mendelian randomized (MR) study. Genetic instruments for tea intake were identified from a genome-wide association study (GWAS) involving 447,385 individuals. Data on lung diseases were collected from a variety of publicly available genome-wide association studies. The main method used for MR analysis is the inverse variance weighting (IVW) method. To ensure the accuracy of the findings, further sensitivity analysis was conducted. RESULTS: The IVW method in our MR analysis revealed no evidence to support a causal relationship between tea intake and lung diseases (IPF: OR = 0.997, 95% CI = 0.994-1.000, p = 0.065; Lung cancer: OR = 1.003, 95% CI = 0.998-1.008, P = 0.261; COPD: OR = 1.001, 95% CI = 0.993-1.006, p = 0.552; acute bronchitis: OR = 0.919, 95% CI = 0.536-1.576, p = 0.759; tuberculosis: OR = 1.002, 95% CI = 0.998-1.008, p = 0.301; pneumonia: OR = 0.789, 95% CI = 0.583-1.068, p = 0.125). The reliability of the results was further demonstrated by four additional MR analysis techniques and additional sensitivity testing. CONCLUSION: We found no evidence of a link between tea intake on lung diseases in our MR results based on genetic information.

Does frequent tea consumption provide any benefit to cognitive function in older adults? Evidence from a national survey from China in 2018.

Objectives: This present study aims to investigate the effect of tea consumption on cognitive function and examine possible psychosocial mechanisms in older adults. Participants and methods: The data of this study came from the 2018 wave of the Chinese Longitudinal Healthy Longevity Survey(CLHLS), and a total of 11,910 valid samples were included. We used ordinary least squares (OLS) to explore whether frequent tea consumption had significant effect on the cognitive function of older people. The problem of endogeneity was addressed by using a propensity score matching (PSM). Then we further explored the psychosocial mechanisms of the effect using a stepwise regression approach. Results: Frequent tea consumption produced a positive effect on Mini-Mental State Examination (MMSE) score (coefficient = 0.340, p < 0.01), and PSM showed similar results. Specifically, the positive effect of green tea (coefficient 0.409, p < 0.01) was significantly greater than the other teas (coefficient 0.261, p < 0.1). Moreover, frequent tea drinkers were 59.7, 74.8, and 81.8% less likely to have severe, moderate and mild cognitive impairment respectively, compared to infrequent tea drinkers (p < 0.01). Levels of depression and sleep quality had partial mediation effect for frequent tea consumption on cognitive function, accounting for 27.6 and 3.5% of the total effect, respectively. Conclusion: Frequent tea consumption was found to have beneficial effects on cognitive function, especially in older people with green tea intake. Sleep quality and levels of depression partially mediated the association between frequent tea consumption and cognitive function among Chinese older adults.

Causal Association Between Tea Consumption and Gout: A Mendelian Randomization Study.

OBJECTIVE: Evidence from prospective studies on the consumption of tea and risk of gout is conflicting and limited. We aimed to investigate the potential causal effects of tea intake on gout using Mendelian randomization (MR). METHODS: Genome-wide association studies in UK Biobank included 349 376 individuals and successfully discovered single-nucleotide polymorphisms linked to consumption of one cup of tea per day. Summary statistics from the Chronic Kidney Disease Genetics consortium included 13 179 cases and 750 634 controls for gout. Two-sample MR analyses were used to evaluate the relationship between tea consumption and gout risk. The inverse-variance weighted (IVW) method was used for primary analysis, and sensitivity analyses were also conducted to validate the potential causal effect. RESULTS: In this study, the genetically predicted increase in tea consumption per cup was associated with a lower risk of gout in the IVW method (OR: 0.90; 95% CI: 0.82-0.98). Similar results were found in weighted median methods (OR: 0.88; 95% CI: 0.78-1.00), while no significant associations were found in MR-Egger (OR: 0.89; 95% CI: 0.71-1.11), weighted mode (OR: 0.80; 95% CI: 0.65-0.99), and simple mode (OR: 1.01; 95% CI: 0.75-1.36). In addition, no evidence of pleiotropy was detected by MR-Egger regression (P=0.95) or MR-PRESSO analysis (P=0.07). CONCLUSION: This study provides evidence for the daily consumption of an extra cup of tea to reduce the risk of gout.

Daily higher tea consumption is associated with a reduced risk of type 2 diabetes: A cohort study and updated systematic review and meta-analysis.

Tea is abundant in phytochemicals (such as polyphenols and theaflavins), which have a hypoglycemic effect. Previous studies investigating the relationship between tea consumption and the risk of type 2 diabetes mellitus (T2DM) have yielded inconsistent results. We hypothesized that tea consumption would be associated with a reduced risk of T2DM. This cohort study used data from the China Health and Nutrition Survey, involving a total of 5199 participants initially recruited in 1997 and subsequently followed until 2009. Consumption of any variety of tea was tracked using structured questionnaires, and T2DM was diagnosed according to the American Diabetes Association's criteria. We also performed a systematic literature search of PubMed, Web of Science, and EMBASE for publications through September 2021, including 19 cohort studies comprising 1,076,311 participants. In our cohort study, the logistic regression model showed a relative risk (RR) of T2DM among tea drinkers of 1.02 (95% confidence interval [CI], 0.82-1.28) compared with non-tea drinkers. Although our updated meta-analysis showed no significant association between tea consumption and T2DM on the whole (pooled RR of 0.96 [0.91-1.00]), compared with the non-tea-drinking group, participants consuming 4 or more cups of tea per day had a 17% reduced risk of T2DM, with an RR of 0.83 (95% CI, 0.76-0.90). These data support our hypothesis that tea consumption at higher doses (e.g., ≥4 cups/day) is associated with a reduced risk of T2DM.

Association between tea consumption and colorectal cancer: a systematic review and meta-analysis of a population-based study.

PURPOSE: A meta-analysis study was performed to systematically assess the association between tea consumption and CRC risk. METHODS: Cochrane Library, Embase, PubMed, and Web of Science were retrieved to collect articles in English since 24 July 2023. Databases were searched and evaluated by two reviewers independently.We screened the literature based on inclusion and exclusion criteria. After determining the random effect model or fixed utility model based on a heterogeneity test, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. RESULTS: We included fourteen articles in this meta-analysis. We analyzed the data using a random effect model to explore the association between tea consumption and CRC because of apparent heterogeneity (P < 0.001, I2 = 99.5%). The combined results of all tests showed that there is no statistically significant association between tea consumption and CRC risk (OR = 0.756, 95%CI = 0.470-1.215, P = 0.247). Subsequently, subgroup analysis and sensitivity analysis were performed. Excluding any single study, the overall results ranged from 0.73 (95%CI = 0.44-1.20) to 0.86 (95%CI = 0.53-1.40). It was determined that there was no significant publication bias between tea consumption and CRC risk (P = 0.064) by Egger's tests. CONCLUSIONS: The results indicated that tea consumption may not be significantly associated with the development of CRC. IMPLICATIONS OF KEY FINDINGS: Tea reduces colon cancer risk by 24%, but the estimate is uncertain. The actual effect on risk can range from a reduction of 51% to an increase of 18%, but regional and population differences may cause differences.

The Association between Coffee and Tea Consumption at Midlife and Risk of Dementia Later in Life: The HUNT Study.

BACKGROUND: Studies exploring the possible protective effect of coffee and tea consumption on dementia have shown inconsistent results so far. We aimed to investigate whether consumption of tea and different types of coffee at midlife are associated with dementia later in life and whether sex or ApoE4 influence such association. METHODS: We included 7381 participants from the Norwegian HUNT Study. Self-reported questionnaires assessed daily consumption of coffee and tea at baseline. After 22 years, individuals 70 years or older were screened for cognitive impairment. RESULTS: General coffee consumption and tea consumption was not associated with dementia risk. Compared to daily consumption of 0-1 cups of coffee, daily consumption of ≥8 cups of boiled coffee was associated with increased dementia risk in women (OR: 1.83, 95% CI: 1.10-3.04, p-value for trend = 0.03) and daily consumption of 4-5 cups of other types of coffee was associated with a decrease in dementia risk in men (OR: 0.48, 95% CI: 0.32-0.72, p-value for trend = 0.05). Furthermore, the association between boiled coffee and increased dementia risk was only found in ApoE4 non-carriers. Differences by sex or ApoE4 carrier status were not supported by strong statistical evidence for interaction. Tea consumption was not associated with dementia risk. CONCLUSION: type of coffee may play a role in the direction of the association between coffee-drinking habits and dementia later in life.

Alcohol intake masked the protective effects of tea consumption against all-cause mortality and blood pressure progression: Findings from CHNS cohort, 1993-2011.

OBJECTIVES: Whether the protective effects of tea consumption interact with the status of alcohol consumption remains unknown. The present study aimed to investigate the relationship between tea consumption and mortality and blood pressure changes between alcohol consumers and non-consumers in a Chinese population. METHODS: This study was conducted with a cohort of 6387 participants from the China Health and Nutrition Survey data between 1993 and 2011. Group-based trajectory modeling was conducted to identify distinct tea consumption trajectories. Kaplan-Meier and Cox regression methods were used to estimate the cumulative rate of all-cause mortality. Restricted cubic spline was performed to determine the nonlinear relationships between mean tea consumption and mortality. Generalized linear mixed-effects models (GLMM) were conducted to assess the blood pressure changes among tea consumption trajectories. RESULTS: We identified three tea consumption trajectories. After a median follow-up of 17.9 y, 580 (9.1%) participants died. The association between tea consumption and death interacted with alcohol drinking status. A lower morality risk for the high tea consumption trajectory was observed only in non-alcohol drinkers (hazard ratio, 0.56; 95% confidence interval, 0.40-0.77). The tea-mortality association was linear in current alcohol drinkers (Plinear = 0.002), demonstrating that mortality increased with increasing tea consumption. The results of GLMM showed that alcohol intake masked the protective effect against blood pressure progression. CONCLUSIONS: The results of this study demonstrated that individuals with a long-term high tea consumption trajectory had a lower risk for all-cause mortality and a slower blood pressure growth rate. The beneficial effects of tea consumption were attenuated by alcohol intake or even harmful to health.

Caffeine and the Risk of Diabetic Retinopathy in Type 2 Diabetes Mellitus: Findings from Clinical and Experimental Studies.

The aim of this study was to assess the potential benefits of caffeine intake in protecting against the development of diabetic retinopathy (DR) in subjects with type 2 diabetes (T2D). Furthermore, we tested the effect of topical administration of caffeine on the early stages of DR in an experimental model of DR. In the cross-sectional study, a total of 144 subjects with DR and 147 individuals without DR were assessed. DR was assessed by an experienced ophthalmologist. A validated food frequency questionnaire (FFQ) was administered. In the experimental model, a total of 20 mice were included. One drop (5 µL) of caffeine (5 mg/mL) (n = 10) or vehicle (5 µL PBS, pH 7.4) (n = 10) was randomly administered directly onto the superior corneal surface twice daily for two weeks in each eye. Glial activation and retinal vascular permeability were assessed using standard methods. In the cross-sectional study in humans, the adjusted-multivariable model showed that a moderate and high (Q2 and Q4) caffeine intake had a protective effect of DR (odds ratio (95% confidence interval) = 0.35 (0.16-0.78); p = 0.011 and 0.35 (0.16-0.77); p = 0.010, respectively). In the experimental model, the administration of caffeine did not improve either reactive gliosis or retinal vascular permeability. Our results suggest a dose-dependent protective effect of caffeine in the development of DR, while the potential benefits of antioxidants in coffee and tea should also be considered. Further research is needed to establish the benefits and mechanisms of caffeinated beverages in the development of DR.

The association between tea consumption and blood pressure in the adult population in Southwest China.

OBJECTIVES: Prior research on the effect of tea consumption on blood pressure (BP) generated inconsistent findings. The objective of this study was to explore the effects of different types of tea consumption on BP. METHODS: We included 76,673 participants aged 30-79 from the baseline data of the China Multi-Ethnic Cohort (CMEC) study. Binary logistic regression was used to analyze the influences of different types of tea consumption on the risk of hypertensive BP. Moreover, multiple linear regression was used to examine the association between tea drinking and BP. RESULTS: Tea consumption was associated with a reduced risk of hypertensive BP by 10% (AOR: 0.90, 95%CI: 0.86-0.94). While dark tea was related to a 1.79-5.31 mmHg reduction in systolic blood pressure (SBP) and a 0.47-1.02 mmHg reduction in diastolic blood pressure (DBP), sweet tea, regardless of the duration, frequency, or amount of consumption, significantly was associated with a reduced SBP by 3.19-7.18 mmHg. Green tea also was associated with a reduced SBP by 1.21-2.98 mmHg. Although scented tea was related to reduced SBP by 1.26-2.48 mmHg, the greatest effect came from the long duration (> 40 years:ß=-2.17 mmHg, 95%CI=-3.47 mmHg --0.87 mmHg), low frequency (1-2 d/w: ß = -2.48 mmHg, 95%CI=-3.76 mmHg--1.20 mmHg), and low amount (≤ 2 g/d: ß=-2.21 mmHg, 95%CI=-3.01 mmHg--1.40 mmHg). Additionally, scented tea was correlated to a decrease in DBP at the frequency of 1-2 d/w (ß=-0.84 mmHg, 95%CI=-1.65 mmHg--0.02 mmHg). Drinking black tea only was associated with lowered SBP. The protective effect of black tea on SBP was characterized by the long-duration (> 15 years, -2.63--5.76 mmHg), high frequency (6-7 d/w, -2.43 mmHg), and medium amount (2.1-4.0 g/d, -3.06 mmHg). CONCLUSION: Tea consumption was associated with lower SBP and a reduced risk of hypertensive BP. The antihypertensive effect varies across types of tea consumed.