A coffee a day may keep the doctor away – study links green tea and coffee consumption with a lower risk of death, but its observations are far from conclusive.
A cuppa can certainly feel like a lifesaver. Now, research suggests that drinking green tea and coffee may lower the risk of death.
Scientists have linked drinking a daily cup of coffee with a lower risk of death among both stroke survivors and healthy people, while drinking seven or more cups of green tea was associated with a lower risk of death among both heart attack and stroke survivors.
The researchers from Osaka University studied the association between a brew, heart health and risk of death in 46,000 participants aged 40 to 79 across different communities in Japan for around 18 years.
Their results indicated that stroke survivors drinking seven or more cups daily had a 62 per cent lower risk of death than stroke survivors who barely drank green tea. A similar association was found for male survivors of heart attacks. However, for participants with no previous heart problems, the reduced risk correlated to green tea was not observed.
Professor Naveed Sattar, a medical researcher and expert on heart health, is wary of results like these. He said, “62 per cent is huge. A statin doesn’t do that, blood pressure treatment doesn’t do that. The size of effect along with the fact that they don’t see it in people without seems to be residual confounding factors.”
“There’s no good evidence that certain nutrients will be more or less beneficial whether or not you’ve had a heart attack. It depends on behaviour and activity. It may be that people who post-stroke are fit enough to go and get themselves seven cups of green tea are healthier anyway,” he added.
It is still unclear what the relationship between green tea or coffee and heart health is, but the study’s researchers think that a polyphenol compound abundant in green tea may be related to the observed lowered risk. Currently, they cannot explain these protective influences and conclude that more research is needed.
Sattar is sceptical that any one thing in tea that could impact our heart health, especially polyphenols. A short-term randomised trial comparing polyphenol-rich to non-polyphenol-rich drinks found no benefits at all of polyphenol-rich drinks on risk factors associated with heart health.
“Would I advise people to go and drink green tea to get health benefits? The answer would be no. I would advise them to do the things we know that work: cut salt in your diet, eat more fruit, veg and fibre, lower calories, be physically active. For nutrition, increasing the fibre in your diet is key – there is some randomised trial evidence that fibre improves risk factors,” said Sattar.
Professor Hiroyasu Iso, lead author on the report, also said that they need lifestyle information on the participants to fully understand their observation. He added that the potential health benefits may depend on how you make the tea or coffee.
“An important distinction to make is that in Japanese culture, green tea is generally prepared with water and without sugar. Additionally, coffee is prepared with water and occasionally milk and sugar,” said Iso.
Avoiding excessive milk or sugar is the healthiest way to drink tea and coffee, limiting sugar-related heart problems.
Although they adjusted their findings for some confounding variables, like history of smoking or diabetes, the researchers highlight false-reporting from participants limit the conclusions they can draw.
“The bottom line is it’s an interesting observation but far from causation. To take it forward, it needs robust randomised trials on relevant risk factors like blood pressure, cholesterol, or diabetes,” said Sattar.
Though green tea and coffee are not exactly health hacks, future research will help us better understand the important lifestyle and nutrition factors for longer, healthier lives. We might as well stick the kettle on in the meantime.