Nick Carne
Tea is good for you, according to new research from – perhaps not surprisingly – China.
Habitual consumption – defined as at least three times a week – is associated with lower risks of cardiovascular disease and all-cause death, according to Xinyan Wang from the Chinese Academy of Medical Sciences.
In other words, it contributes both to longer life expectancy and more healthy years of life.
The favourable health effects appear to be particularly robust for green tea and for those with a long-term love of it.
In their study, Wang and colleagues followed 100,902 participants in the China-PAR Project who had no history of heart attack, stroke or cancer for a median of 7.3 years. All were classified into one of two groups – habitual and never / non-habitual.
Regular drinkers were found to have a 20% lower risk of incident heart disease and stroke, a 22% lower risk of fatal heart disease and stroke, and a 15% decreased risk of all-cause death.
The analyses estimated, for example, that 50-year-old habitual tea drinkers would develop coronary heart disease and stroke 1.41 years later and live 1.26 years longer than those who never or seldom drank tea.
The potential influence of changes in tea drinking behaviour were analysed in a subset of 14,081 participants with assessments at two time points.
Habitual drinkers who maintained their habit had a 39% lower risk of incident heart disease and stroke, 56% lower risk of fatal heart disease and stroke, and 29% decreased risk of all-cause death compared to consistent never or non-habitual tea drinkers.
“Mechanism studies have suggested that the main bioactive compounds in tea, namely polyphenols, are not stored in the body long-term,” says Dongfeng Gu, senior author of a paper in the European Journal of Preventive Cardiology.
“Thus, frequent tea intake over an extended period may be necessary for the cardioprotective effect.”
The study found green tea to be more beneficial than black, though Gu acknowledges that may be because of the preferences of those studied. Only a few preferred black tea.
Nevertheless, the researchers say their findings “hint at a differential effect between tea types” – and suggest two factors may be at play.
First, green tea is a rich source of the polyphenols which protect against cardiovascular disease and its risk factors, but black tea is fully fermented and during this process polyphenols are oxidised into pigments and may lose their antioxidant effects.
Second, black tea is often served with milk, which previous research has shown may counteract the favourable health effects of tea on vascular function.
