The health benefits of green tea are well-established, but black tea might be a good idea too, according to a new analysis.
The study, published in Annals of Internal Medicine, draws on data from nearly half a million people to find a link between black tea drinking and lower mortality risk.
The researchers, who are based at the US National Institute of Health, examined data from the long-term UK Biobank study, which tracked a cohort of 502,488 UK residents aged between 40 and 69.
Between 2006 and 2010, participants in this study regularly logged a range of lifestyle, and health-related information via touchscreens at assessment centres. This information included tea drinking, by number of cups per day.
Among the 498,043 participants who logged tea-drinking information, 85% reported regularly drinking tea. Nearly a fifth of participants (19%) reported drinking more than six cups of tea per day.
A separate survey of a smaller cohort of participants suggested that 89% of the tea drinkers drank black tea, while 7% drank green tea.
According to the UN, the UK consumes around 100,000 tonnes of tea each year – or about 1.5 kilograms per person.
The American researchers combined the tea-drinking information in the UK with mortality data.
Once they’d adjusted for age and demographics, they found that participants who drank at least two cups of tea per day had a 9-13% lower risk of dying.
Drinking 2-3 cups per day was associated with the lowest mortality risk, but even drinking 10 or more cups was linked to a lower mortality risk than drinking no tea at all.
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In their paper, the researchers say that their findings reflect similar studies based in China and Japan, where green tea is much more common than black.
“Fewer studies have assessed tea intake and mortality in populations where black tea is predominantly consumed, such as in the United States and Europe, and results have varied across studies,” write the researchers.
They point out, however, that they didn’t track some “potentially important aspects” like tea strength or cup size, making it harder to draw precise conclusions.
While the study is observational and thus can’t establish a cause, the researchers point out that the polyphenols and flavonoids in black tea have been linked to a variety of health benefits in small randomized-control trials – including lower cholesterol, and a lower risk of carcinogenesis and type 2 diabetes.
“These findings provide reassurance to tea drinkers and suggest that black tea can be part of a healthy diet,” write the researchers.