Tea question: how was the usual drink associated with vascular health

Tea drinkers were less likely to experience vascular diseases than people who did not drink it. This was shown by a study of almost half a million Chinese residents, who were monitored for about nine years. Regular consumption of the drink was associated with a lower risk of disease, and the results varied depending on the type, strength, and temperature of the tea. Which tea turned out to be associated with the most favorable indicators and why scientists do not advise taking six to eight cups a day as the norm – in the Izvestia article.

What did the observation of almost half a million people show?

The study included 485,934 Chinese adults. The median follow—up duration was 9.05 years, which means that half of the participants had a shorter follow-up period, while the other half had a longer one.

During this time, 14,863 cases of diseases included in the analysis were registered. The scientists took into account cardiovascular and cerebrovascular diseases, that is, those associated with the vessels of the brain, as well as pulmonary heart and peripheral artery diseases.

Regular tea consumption was associated with an 11% reduction in the relative risk of the outcomes studied, compared with no such habit. At the same time, the researchers did not limit themselves to dividing the participants into tea lovers and those who do not drink it: they also considered the amount of the drink, its type, strength and temperature.

This kind of detail is important for understanding the habit. The word "tea" combines different methods of preparation and consumption, so one common indicator does not describe all the differences between the participants.

Which means an 11% reduction in risk%

The number 11% describes the relative difference between the groups being compared. It does not mean that tea prevents illness in 11 out of every hundred people or reduces the likelihood of illness by 11 percentage points.

The absolute difference depends on how often the disease occurs in the initial group. The lower the initial probability, the smaller the absolute change with the same relative decrease. Therefore, one percent cannot be used to calculate the personal benefit for a particular person.

It is also important how the work was arranged. This is an observational study: scientists compared people's habits with subsequent illnesses. Participants were not randomly assigned to drink a certain amount of tea or refuse it.

This approach makes it possible to identify stable connections in everyday life. However, the question remains as to how much of the difference is related to the drink itself, and how much is related to other characteristics of the people who choose it.

Black, green and scalding hot

In the new work, the feedback on vascular diseases for black tea turned out to be more consistent than for green tea. In other words, more regular consumption of black tea was more consistently associated with a lower risk of the diseases studied.

This observation does not give grounds to declare green tea useless or recommend that everyone change the variety. A more consistent statistical relationship by itself does not prove the superiority of one drink over another.

Differences were also found depending on the fortress. The lowest risk was associated with medium-strength tea. Consequently, the results do not support the notion that a richer infusion is necessarily healthier.

For scalding hot tea, the researchers, on the contrary, found an association with increased vascular risk. At the same time, it is impossible to deduce from the short message the specific temperature from which the drink became dangerous.

Charalampos Rallis, a specialist in genetics, genomics and fundamental cell biology at Queen Mary University of London, noted in a commentary at the Science Media Center that the authors had made many comparisons. Therefore, the results of black and scalding hot tea should be considered as preliminary and requiring further verification.

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Why didn't six to eight cups become a recommendation?

Among the participants who consumed tea at least weekly, the minimum calculated risk was observed at about six to eight cups per day. This figure describes the result of a statistical analysis of a specific sample.

The study did not check whether a person would become healthier if he increased the usual amount of drink to this level. It also does not establish a universal serving suitable for people of different ages and health conditions.

Because of this, the number of cups cannot be confidently translated into a single volume in milliliters. A single assessment also does not reflect all possible changes in habits over the years of observation.

For a practical recommendation, you need to know more: what volume and cooking method are being compared, who is suitable for such a habit, and whether changing it really reduces the number of diseases.