A study of nearly half a million adults in China has found that people who drink tea regularly were less likely to develop diseases affecting the heart and blood vessels than those who did not, according to Science Daily. The research, published in the Journal of Internal Medicine, followed 485,934 participants for a median of 9.05 years and recorded 14,863 cases of vascular disease. Regular tea consumption was associated with an 11% lower risk across the combined vascular outcomes examined.
The findings come with qualifications. Because the study was observational, it can show connections between tea habits and health outcomes but cannot prove that tea itself caused the differences, Science Daily reports.
Why it matters
Vascular diseases interfere with blood circulation, which carries oxygen and nutrients to organs and tissues. The conditions tracked in the study included cardiovascular disease, which affects the heart and blood vessels; cerebrovascular disease, which involves the vessels supplying the brain; pulmonary heart disease, in which lung or lung-vessel problems strain the heart; and peripheral artery disease, in which arteries carrying blood to areas such as the legs narrow or become blocked.
Heart and circulatory conditions remain a leading burden on health systems worldwide, so even modest associations found in a very large population are of interest to researchers. The study also suggests that how tea is drunk — not just whether it is drunk — may matter, a nuance that earlier work on the beverage has often glossed over.
What the researchers found
Among participants who drank tea at least once a week, the lowest estimated risk appeared at roughly six to eight cups per day, according to the reporting. The authors did not conclude that drinking more tea prevents disease or that everyone should aim for that amount.
Black tea showed more consistent links to reduced vascular risk than green tea. Both come from the same plant, Camellia sinensis, but are processed differently: black tea is allowed to oxidize extensively, while green tea is processed to limit oxidation. Tea contains polyphenols, plant compounds that have drawn scientific attention for their antioxidant properties and possible effects on blood vessel function. The study did not establish whether these compounds explain the gap between black and green tea.
Strength also appeared relevant. Participants who drank tea of moderate strength had the lowest associated risk, suggesting that brewing it stronger did not correspond to greater benefit.
The most striking result concerned temperature. Tea described as "burning hot" was linked to an increased risk, a finding that raises questions about whether certain drinking habits could offset some of the favorable associations seen with regular consumption. Very hot drinks expose tissues in the mouth and digestive tract to high temperatures, but the study did not identify a biological mechanism for the vascular risk or a specific temperature at which tea becomes harmful. The results should not be read as proof that extremely hot tea causes vascular disease.
Lifestyle context
The researchers also looked at how tea drinking interacted with smoking and physical activity. Their analysis found that people who drank tea habitually, did not currently smoke, and were highly physically active had the lowest vascular disease risk of any group.
"Joint analyses showed that tea consumption, smoking status and physical [activity] were collectively associated with vascular risk, with the favorable combination of habitual tea consumption, non-current smoking and high physical activity associated with the lowest risk," the authors wrote, as quoted in the reporting.
That combination points to overall lifestyle rather than any single food or drink. Physical activity supports circulation, helps regulate blood pressure and aids heart and blood vessel function, while avoiding smoking limits exposure to substances that damage blood vessels.
What to watch
The study offers encouraging evidence that a widely consumed beverage is associated with cardiovascular health, but it leaves the central question open: whether tea directly influences disease risk. Further research would be needed to answer that, and to pin down why black tea, moderate strength and cooler serving temperatures showed more favorable associations than their alternatives.
