A UK study was conducted among half a million people, all participants in a large cohort study called “UK Biobank” from 2006 and 2010.
Dietary questionnaires were administered at enrollment and during follow-up of median 11.2 years about tea-drinking habits, specifically about the number of cups of tea and other drinks and also about drinking the tea very hot, hot or warm. Information on death and cause of death were also gathered from the participants.
Eighty five percent of the participants reported tea drinking, 89 % of those who reported tea type drank black tea. When compared to non-tea drinkers, those who took 2 or more cups daily had 9 to 13 % lower risk for CVD and other mortality. Tea drinking had a beneficial effect on mortality regardless of whether they drank coffee or not. Adding milk or sugar to tea and altered (lowered) caffeine metabolism rate did nor affect the results.
Unmeasured confounding factors could influence tea-drinking behavior and the risk of death, but probably did not attenuate the associations found.
The findings of this study suggest that (black) tea drinking may be associated with modestly lower mortality. There is no definitive proof that tea drinking directly reduced the risk of mortality. However, these findings provide reassurance to tea drinkers and suggest that black tea can be part of a healthy diet.
Several experts later expressed caution over the tea drinking claim explaining that it might be that tea drinkers avoid more harmful sugary drinks and have other health behaviors that might lead to a lower risk for type 2 diabetes. After all this was an observational study. The important take-home message is that lifestyle is crucial in managing risk of developing type 2 diabetes and drinking unsweetened tea can be part of this healthy lifestyle.