Tea has long been regarded as one of the healthier beverage choices, and a major study tracking almost half a million adults over roughly nine years adds to the evidence supporting that view. Researchers found that people who drank tea regularly were less likely to develop cardiovascular disease than those who rarely or never consumed it. However, one factor appeared to significantly influence the outcome: temperature.
The research, led by Zichen Ye of the Chinese Academy of Medical Sciences and Peking Union Medical College, analysed health data from the China Kadoorie Biobank, one of the world's largest long-term population studies. Collaborators included researchers from the Peking University Health Science Center, the University of Hong Kong and Sun Yat-sen University.
Nearly half a million participants tracked
The study followed 485,934 adults aged between 30 and 79 after excluding those who already had cancer, heart disease or a history of stroke. Participants were recruited between 2004 and 2008 from urban and rural regions across China.
At the start of the study, the average participant was 52 years old and women accounted for 59% of the sample.
Among them, 148,229 people reported drinking tea regularly. Tea drinking was considerably more common among men than women, with about half of male participants consuming tea at least weekly compared with roughly one in five women.
Tea drinkers showed lower cardiovascular risk
Over the follow-up period, 14,863 participants developed cardiovascular disease, including heart attacks, strokes and peripheral artery disease.
After accounting for factors such as age, sex, education, smoking, alcohol consumption, physical activity, weight and medical history, researchers found that habitual tea drinkers had an 11% lower risk of developing cardiovascular disease than non-drinkers or occasional drinkers.
The findings were particularly pronounced for certain conditions:
- 37% lower risk of ischaemic stroke (strokes caused by blocked blood vessels).
- 17% lower risk of heart attack.
The study did not identify a clear relationship between tea consumption and haemorrhagic stroke or heart problems associated with lung disease.
The temperature made a difference
One of the most striking findings involved how hot participants preferred their tea.
Those who reported drinking tea at hot or room temperature had approximately 17% lower cardiovascular risk compared with people who rarely drank tea.
By contrast, participants who said they consumed their tea burning hot had a 16% higher risk of cardiovascular disease.
Ye suggested that one practical takeaway is simple: allow tea to cool slightly before drinking it.
Although previous research has linked very hot beverages with damage to the upper digestive tract, researchers cautioned that it remains unclear why extremely hot tea might be associated with higher cardiovascular risk.
Strength and type of tea also mattered
The study found that moderately strong tea was associated with the greatest apparent benefit, reducing cardiovascular risk by around 13% compared with people who rarely drank tea.
The advantage linked to stronger brews was less consistent and may have been due to chance.
Researchers also observed that black tea showed a more consistent association with lower cardiovascular risk than green tea, a finding that differs from many earlier studies.
The authors suggested that compounds produced during the fermentation process of black tea could play a role, although they stressed that lifestyle and regional factors may also have influenced the results.
Ye cautioned against interpreting the findings as evidence that black tea is inherently healthier or that tea drinkers should switch varieties.
More was not necessarily better
Among the 160,466 participants who drank tea at least once a week, average consumption was just under three cups per day.
The analysis suggested that cardiovascular risk continued to decline as tea intake increased, reaching its lowest point at roughly seven cups daily. At that level, risk appeared around 35% lower than among those consuming very small amounts of tea.
However, the apparent benefit levelled off and gradually diminished at extremely high consumption levels, disappearing among people drinking more than approximately 21 cups per day.
Researchers emphasised that these findings should not be interpreted as a recommendation to drink seven cups of tea daily, noting that serving sizes, brewing methods and tea strength vary considerably.
Lifestyle remained the biggest factor
Tea was only one part of a broader picture.
When researchers compared participants according to smoking status, physical activity and tea consumption, they found that people who:
- drank tea regularly,
- did not currently smoke,
- and maintained high levels of physical activity,
experienced a 45% lower rate of cardiovascular disease than sedentary smokers who did not drink tea.
Even so, researchers stressed that stopping smoking and maintaining regular exercise remain vastly more important and better-established methods of reducing cardiovascular risk than drinking tea.
As Ye noted, tea should be viewed as one component of a healthy lifestyle, not as a substitute for proven preventive measures.
Important limitations
The authors acknowledged several limitations.
Tea habits were recorded only once at the beginning of the study, meaning changes in participants' drinking behaviour over time were not captured. Tea temperature and strength were also self-reported rather than objectively measured.
In addition, the analysis did not adjust for coffee consumption, overall dietary patterns or stress levels, all of which may influence cardiovascular health.
Because participants were recruited in China nearly two decades ago, the findings may not apply directly to populations with different tea-drinking habits.
Most importantly, the study was observational. While it identified associations between tea drinking and lower cardiovascular risk, it cannot prove that tea itself caused the difference.
The researchers say future studies will aim to track tea consumption over time, measure biological markers of tea intake and use methods designed to investigate cause-and-effect relationships more directly.
Source: earth.com
