While green tea has a long-standing reputation for health benefits, research has been 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 the United Kingdom, where black tea drinking is common. After surveying about 500,000 people and following them for a median of 11 years, the results, published Aug. 29 in the journal Annals of Internal Medicine, gave black tea a boost. Among the population of tea drinkers—89% of whom drank black tea, compared to 7% who drank green—drinking tea was associated with a modestly lower mortality risk for those who had two or more cups a day compared to non-drinkers. People who added milk or sugar also experienced the benefit, and the results remained consistent regardless of the tea’s temperature. The findings also indicate that tea drinkers had a lower risk of dying from cardiovascular disease, ischemic heart disease, and stroke than those who didn’t drink tea.
While it’s difficult to say why people who drink tea may live longer, it’s not entirely a surprise. According to Inoue-Choi, tea is “very rich in bioactive compounds” that reduce stress and inflammation, including polyphenols and flavonoids.
A 2020 study that used the same British database as the new research found that there’s an association between higher consumption of both black and green tea and biomarkers that predict cardiometabolic health, including lower cholesterol levels. Research has also suggested that tea can help lower blood pressure.
Going forward, researchers should take a closer look at the connection between tea and cardiovascular disease, says Rob M. van Dam, professor of exercise and nutrition sciences at George Washington University’s Milken Institute School of Public Health, who did not participate in the study. One striking thing about the new research, he notes, is that there isn’t an association between increasing the dose of tea—the amount a person consumes—and decreased mortality after the person had consumed two or three cups. The exception, he said, is if you eliminate coffee drinkers, who may have made it harder to spot an association between increasing the amount of tea you drink and mortality because they had lower mortality during the study. Without the coffee drinkers, it became clearer that drinking tea was associated with a lower risk of dying of heart disease. “The association between tea consumption and cardiovascular mortality may be driving the association between tea consumption and all-cause mortality,” van Dam says.
None of this is to say, however, that you should run to your kettle. The new research is based on an observational study—meaning that the evidence wasn’t gathered from an experiment, and the results were inferred by the researchers. The findings shouldn’t be used to make health decisions, and must be replicated in randomized clinical trials, experts say. Plus, the magnitude of the association between tea drinking and mortality was modest, which means it’s likely that another characteristic of people who drink tea could have led to this effect, says van Dam. For instance, people who drink tea might hypothetically have been less likely to consume soft drinks.
As Inoue-Choi put it, the new findings should be reassuring to people who drink tea regularly. But “people shouldn’t change how many cups of tea to drink every day because of these results,” she says.