In a recent study published in feed Journal, researchers investigated whether the protective effects of tea intake against hypertension and mortality interact with alcohol intake among chinese individuals.
Stady: Alcohol intake masks the protective effects of tea consumption against all-cause mortality and blood pressure progression: results from the CHNS cohort, 1993–2011.. Image credit: iroKlyngz / Shutterstock.com
Tea is a beverage that is widely consumed all over the world. Recently published studies have reported the beneficial effects of tea against various medical conditions, including high blood pressure, cardiovascular disorders, diabetes, stroke, heart attack, and mortality.
However, several factors, such as milk content, smoking habits, coffee intake, lifestyle, and gender, can reduce the health benefits of consuming tea.
However, data on possible interactions of alcohol and tea with regard to outcomes such as hypertension and mortality are limited.
In this large-scale prospective cohort study, researchers investigated the relationship between tea intake, blood pressure (BP) changes, and death among heavy drinkers compared to non-drinkers in China.
The study included 6387 individuals in the Chinese Health and Nutrition Survey (CHNS) and was conducted in the period 1993-2011.
Individuals with two or more tea intake records, with a minimum of one from 1993, were considered for the current analysis. The team conducted group path modeling (GBTM) to identify distinct long-term pathways for tea drinking over an 18-year period.
Data on tea consumption in the previous year, including average cups of tea consumed per day, were obtained through in-person surveys in follow-up rounds between 1993 and 2011. Individuals who had drunk alcohol in the previous year were considered current alcohol consumers. The results were death from any cause and changes in blood pressure readings.
In the event of death, family members of the deceased were interviewed. The last day of life or the date of the final scan, whichever occurred earlier, was recorded to determine the duration of follow-up.
Cox regression models and Kaplan-Meier statistics were used to assess the cumulative mortality rate. The team used bound cube slices to assess the nonlinearity of the associations between average tea consumption and death.
Generalized linear mixed effects modeling (GLMM) was performed to assess BP adjustments among the tea intake trajectories, and the hazard ratio (HR) was determined by adjusting for covariates such as age, marital status, sex, nationality, residence, education level, occupation, annual family income, smoking habits, and comorbidities (such as diabetes, hypertension, and cancer), antihypertensive medication use, and mean values of body mass index (BMI), waist circumference, and hip circumference.
CHNS data were obtained from 12.0 counties through multistage random cluster sampling. The CHNS cohort was started in 1989 and was followed every two to four years from 1989 to 2015 among more than 30,000 individuals.
Results and discussion
The average age of the individuals is 54 years. 50% of them are male, and 33% of them currently drink alcohol.
Participants were divided into non-tea consumers (no cups of tea consumed per day), light tea consumers (who drank one cup per day), and heavy tea consumers (those who drank three to four cups per day). Among the study participants, 2,838 and 1,478 were light and high tea consumers, respectively.
After a follow-up of 18 years (median), nine percent of the participants died (n = 580). The relationship between tea intake and mortality was influenced by alcohol consumption.
The cumulative mortality rate was lower among heavy tea consumers compared to non-tea consumers (HR 0.8). However, heavy tea consumption reduced the risk of death only among non-alcoholic consumers (HR 0.6).
A linear relationship to tea mortality was observed for current alcohol consumers, suggesting that alcohol masks the benefits of tea against mortality. In addition, according to the results of GLMM modeling, alcohol also blocked the blood pressure-lowering effects of tea. Similar results were obtained in the stratified gender analyses.
Individuals who drank large amounts of tea daily were more likely to be smokers than older males residing in urban areas.
Current alcohol consumers had a higher likelihood of having unhealthy lifestyles, smoking and higher values for BMI and waist and hip circumference than non-drinkers, which may reduce the benefits of tea consumption.
Alcohol is said to reduce the antioxidant activity of tea-derived polyphenols. The blood pressure lowering effects of tea drinking may be due to a delay in the atherosclerosis induced by the tea.
Overall, the results of the study showed that regular consumption of three to four cups of tea reduces the risk of death and prevents high blood pressure. However, the benefits of consuming tea were diminished by consuming alcohol, which was sometimes harmful to health.
The study findings support the beneficial effects of tea intake on mortality, as reported in previous studies, and extend the findings to a larger population in china.
However, the population sample is not representative of the entire nation, and thus, the results have limited generalizability.
Additional research should analyze national data obtained from randomized controlled trials (RCTs), on tea intake, including the type of tea consumed, using objective methods.