Ulol green tea has a longstanding reputation for health benefits, research is much more mixed on black tea. One problem, says Maki Inoue-Choi, an epidemiologist at the National Cancer Institute, is that large observational studies on tea and mortality have focused on countries like Japan or China — places where green tea is more popular.
To fill this gap, Inoue-Choi and her colleagues analyzed data in Great Britain, where drinking black tea is common. After studying about 500,000 people and following them for an average of 11 years, the results, published on August 29 in the journal Annals of Internal Medicine, gave a boost to black tea. Among the population of tea drinkers — 89% of whom drank black tea, compared with 7% who drank green — tea drinking was associated with a modestly lower risk of death for those who drank two or more cups a day, in compared to non-drinkers. People who added milk or sugar also experienced the benefit, and the results remained consistent regardless of the tea temperature. The findings also showed that tea drinkers had a lower risk of death from cardiovascular disease, coronary heart disease and stroke than non-tea drinkers.
While it’s hard to say why people who drink tea may live longer, it’s not a complete surprise. According to Inoue-Choi, tea is “very rich in bioactive compounds” that reduce stress and inflammation, including polyphenols and flavonoids.
And 2020 study which used the same British database as the new study found an association between higher black and green tea consumption and biomarkers that predict cardiometabolic health, including lower cholesterol levels. Research also shows that tea can help lower Blood Pressure.
Going forward, researchers should take a closer look at the link between tea and cardiovascular disease, said Rob M. van Dam, a professor of exercise science and nutrition at the George Washington Institute’s School of Public Health, who was not involved in the study. One striking thing about the new study, he notes, is that there was no relationship between increasing tea dosage — the amount a person consumes — and reduced mortality after a person consumed two or three cups. The exception, he said, is if you eliminate coffee drinkers, which may have made it harder to see the link between increasing the amount of tea you drink and mortality, since they had lower mortality during the study. Without coffee drinkers, it became clearer that drinking tea was associated with a lower risk of death from heart disease. “The association between tea consumption and cardiovascular mortality may lead to the association between tea consumption and all-cause mortality,” says van Damme.
However, none of this means you should run to your kettle. The new research is based on an observational study, meaning that the evidence was not collected from an experiment, but the results were made by the researchers. The findings should not be used to make health decisions and should be replicated in randomized clinical trials, experts say. Plus, the magnitude of the association between tea drinking and mortality was modest, meaning it’s likely that another characteristic of tea drinkers led to this effect, van Dam says. For example, tea drinkers might hypothetically be less likely to consume soft drinks.
As Inoue-Choi said, the new findings should be reassuring to regular tea drinkers. But “people shouldn’t change how many cups of tea they drink each day because of these results,” she says.
More must-see stories from TIME