Those who drink more than two cups of tea every day are more likely to live longer than people who do not, says a new study.

The study, published in the Annals of Internal Medicine, showed that relative to tea non-drinkers, participants who reported drinking two or more cups each day had a 9 to 13 per cent lower risk for mortality.

According to the researchers, including Maki Inoue-Choi from National Cancer Institute (NCI), in the US, the findings suggest that tea, even at higher levels of intake, can be part of a healthy diet. Tea is one of the most consumed beverages worldwide.

Previous research has suggested an association between tea consumption and lower mortality risk in populations where green tea is the most common type of tea. In contrast, published studies in populations where black tea drinking is more common are limited with inconsistent findings.

For the study, the research team evaluated the associations of tea consumption with all-cause and cause-specific mortality using data from the UK Biobank, where black tea drinking is common. They also assessed whether the associations differ by the use of common tea additives (milk and sugar), tea temperature, and genetic variants affecting the rate at which people metabolise caffeine.

The UK Biobank includes data on half a million men and women aged 40 to 69, who completed a baseline questionnaire between 2006 and 2010. Of those, 85 per cent reported regularly drinking tea and of them, 89 per cent reported drinking black tea.

The associations were observed regardless of whether participants also drank coffee, added milk or sugar to their tea, their preferred tea temperature, or genetic variants related to caffeine metabolism.