Drinking green tea has long been associated with various health benefits and longevity, according to a number of studies, but now recent data from Britain show that black tea is also associated with health benefits, and linked to a lower mortality risk.
The findings come from a prospective study of nearly 500 000 participants in the UK Biobank cohort, among whom drinking black tea was common. They suggest that drinking black tea may be associated with a moderately lower all-cause mortality risk, and the risk was lowest among those drinking two or more cups of tea per day, reports Medscape.
The study was published in Annals of Internal Medicine.
During median follow-up of 11.2 years, those who drank at least two cups of tea each day had a lower all-cause mortality risk, reported Maki Inoue-Choi, PhD, and colleagues from the National Cancer Institute in Bethesda, Maryland.
After multivariate adjustment, the hazard ratios (HR) for death among tea drinkers, compared with no tea intake, were similar across intake levels: 0.95 for daily intake of up to one cup, 0.87 for 2-3 cups, 0.88 for 4-5 cups, 0.88 for 6-7 cups, 0.91 for 8-9 cups, and 0.89 for 10 or more cups.
Drinking tea also showed an inverse association with mortality from cardiovascular disease (adjusted HRs ranging from 0.98 to 0.76), ischaemic heart disease (aHRs ranging from 1.03 to 0.74), and stroke (aHRs ranging from 0.92 to 0.48 ).
However, the researchers added that “no clear trend was seen for cancer or respiratory disease mortality, with associations among higher intake categories tending toward the null”.
There is "no clear answer” on why no association was observed between tea consumption and cancer mortality in the current study, Inoue-Choi said.
Notably, the effects were apparent, regardless of whether milk or sugar were added to tea, tea temperature, or genetic variations in caffeine metabolism among participants, she said.
She and her colleagues controlled for these factors, as well as numerous others that could confound the results, including coffee consumption and baseline health and demographic characteristics.
Study subjects were 498 043 adults with a mean baseline age of 56.5 years. About 85% reported drinking tea, 90% reported drinking black tea, and most drank 2-3 cups (29%), 4-5 cups (26%), or 6-7 cups (12%) per day.
A limitation of the study is the lack of information on certain aspects of tea intake, such as portion size and tea strength, the authors note.
Tea is among the most frequently consumed beverages worldwide, and studies from places where green tea is popular, like China and Japan, have demonstrated health benefits. Data from places where black tea is more commonly consumed have been lacking and provided conflicting results, she noted.
A presumed mechanism of action related to tea consumption is reduced oxidative stress and inflammation, thanks to “polyphenols and flavonoids, namely catechins and their oxidated products”, the authors said. Oxidative stress and inflammation may promote carcinogenesis, therefore reducing oxidative stress and inflammation may improve endothelial function, they add.
“While these findings may offer reassurance to tea drinkers, they do not indicate that people should start drinking tea or change their tea consumption for health benefits,” she said, explaining that “the results need to be replicated in future studies and extended in other diverse populations.”
Study details
Tea Consumption and All-Cause and Cause-Specific Mortality in the UK Biobank
A Prospective Cohort Study
Maki Inoue-Choi, Yesenia Ramirez, Marilyn C. Cornelis et al.
Published in Annals of Internal Medicine on 30 August 2022
Background
Tea is frequently consumed worldwide, but the association of tea drinking with mortality risk remains inconclusive in populations where black tea is the main type consumed.
Objective
To evaluate the associations of tea consumption with all-cause and cause-specific mortality and potential effect modification by genetic variation in caffeine metabolism.
Design
Prospective cohort study.
Participants
498 043 men and women aged 40 to 69 years who completed the baseline touchscreen questionnaire from 2006 to 2010.
Measurements
Self-reported tea intake and mortality from all causes and leading causes of death, including cancer, all cardiovascular disease (CVD), ischemic heart disease, stroke, and respiratory disease.
Results
During a median follow-up of 11.2 years, higher tea intake was modestly associated with lower all-cause mortality risk among those who drank 2 or more cups per day. Relative to no tea drinking, the hazard ratios (95% CIs) for participants drinking 1 or fewer, 2 to 3, 4 to 5, 6 to 7, 8 to 9, and 10 or more cups per day were 0.95 (95% CI, 0.91 to 1.00), 0.87 (CI, 0.84 to 0.91), 0.88 (CI, 0.84 to 0.91), 0.88 (CI, 0.84 to 0.92), 0.91 (CI, 0.86 to 0.97), and 0.89 (CI, 0.84 to 0.95), respectively. Inverse associations were seen for mortality from all CVD, ischaemic heart disease, and stroke. Findings were similar regardless of whether participants also drank coffee or not or of genetic score for caffeine metabolism.
Limitation
Potentially important aspects of tea intake (for example, portion size and tea strength) were not assessed.
Conclusion
Higher tea intake was associated with lower mortality risk among those drinking 2 or more cups per day, regardless of genetic variation in caffeine metabolism. These findings suggest that tea, even at higher levels of intake, can be part of a healthy diet.
See more from MedicalBrief archives:
Habitual tea drinking cuts CVD and all-risk mortality — China-PAR study
Daily tea and coffee consumption links to lower stroke and dementia risk — UK Biobank
Green tea extract promotes gut health, lowers blood sugar – Ohio study