Drinking tea could be associated with a lower risk of mortality, a study has suggested.

When compared with those who do not drink tea, people who consumed two or more cups each day had between a 9% and 13% lower risk of mortality, researchers said.

The findings, published in the Annals of Internal Medicine, suggested the result was the same no matter whether the person also drank coffee, added milk or sugar to their tea, what their preferred tea temperature was, or whether there were genetic variants involved affecting the rate at which people metabolise caffeine.

The researchers, from the UK National Institutes of Health, used data from the UK Biobank, which saw 85% of the half a million men and women, aged 40 to 69, report that they regularly drink tea.

Of those, 89% said they drank black tea.

The study was conducted with a questionnaire answered from 2006 to 2010 and followed up over more than a decade.

Fernando Rodríguez Artalejo, Professor of Preventive Medicine and Public Health at the Autonomous University of Madrid, described the research as representing "a substantial advance in the field", saying most studies had been done in Asia, where green tea is the most widely consumed, and the few outside Asia were "small in size and inconclusive in their results".

He said: "This article shows that regular consumption of black tea (the most widely consumed tea in Europe) is associated with a modest reduction in total and, especially, cardiovascular disease mortality over 10 years in a middle-aged, mostly white, adult general population."

He said the study does not definitively establish that tea is the cause of the lower mortality of tea drinkers, because it cannot exclude that this is down to other health factors associated with tea consumption.

Another question which remains unanswered is whether people who do not drink tea should start doing so to improve their health.

He said: "Studies should be done with repeated measurements of tea consumption over time and compare the mortality of those who do not consume tea on a sustained basis with that of those who have started to consume tea or have increased their consumption over time, and those who have been drinking tea for years."