A growing body of evidence suggests that drinking several cups of tea a day has many health benefits, including reducing the risk of heart disease, stroke, diabetes and overall mortality.
The latest research on the topic, a review of 19 studies, will be presented at the annual meeting of the European Association for the Study of Diabetes next week. The results suggest that daily consumption of at least four cups of black, green or Oolong tea reduces the risk of developing type 2 diabetes by 17% over a decade.
The research, led by a Chinese team, involved more than one million adults in eight countries. The results indicate that there are fewer benefits associated with drinking fewer cups of tea. One to three cups a day only reduced the risk of type 2 diabetes by 4%, according to the results. The risk of developing diabetes decreased by 1% for each additional daily cup.
“Our results are exciting because they suggest that people can do something as simple as drinking four cups of tea a day to potentially reduce their risk of developing type 2 diabetes,” said Xiaying Li, a researcher at the Wuhan University of Science and Technology. A declaration.
A study published last month found that drinking two or more cups of black tea a day reduced the overall risk of death by 9% to 13% in people in the UK over a 14-year period, compared to those who did not drink tea. The study also found an association between drinking multiple cups of tea and a lower risk of coronary heart disease and stroke.
“We think our findings will be very reassuring to people who already drink tea,” said Dr. Maki Inoue-Choi, a scientist at the National Cancer Institute who led the research.
Inoue-Choi said that even among people in his study who drank more than 10 cups a day, “we found no negative effects on mortality risk.”
Antioxidants in Tea Could Reduce Inflammation
The health benefits of drinking tea may be linked to polyphenols, compounds found naturally in plants that provide antioxidants.
“These compounds can decrease inflammation and oxidative stress in the body, which eventually reduces the risk of developing certain health conditions such as heart disease,” Inoue-Choi said.
The dominant polyphenols in green tea, catechins, may be particularly helpful in preventing disease by protecting cells from damage. When green tea leaves are fermented to make black tea, the catechins turn into theaflavins, another form of antioxidant.
Inoue-Choi said this could explain why green tea and black tea seem to confer health benefits. It could also explain why people need to drink a lot of tea to see a significantly lower risk of disease or death.
Indeed, the Chinese team found in a separate study of 5,200 adults that when they did not take into account the number of cups of tea consumed, the risk of developing type 2 diabetes was about the same for tea drinkers and non-tea drinkers.
In her study, Inoue-Choi said she found that adding milk or sugar to tea did not reduce health benefits, but participants tended to use these ingredients sparingly.
“The sweetened tea from the store has a lot more sugar,” she said. “We should always follow dietary guidelines to avoid too much sugar and too much saturated fat.”
Inoue-Choi’s study, however, found no association between tea drinking and a reduced risk of death from cancer.
Although some previous studies have suggested that drinking tea may reduce the risk of prostate, lung, ovarian, or colorectal cancer, one study also found that drinking three cups of black tea a day was a important risk factor for breast cancer. Another study found that drinking very hot tea (above 149 degrees Fahrenheit) was associated with an increased risk of esophageal cancer.
“Results for cancer have been more mixed,” Inoue-Choi said, adding that more research is needed. “There were more consistent results for heart disease or stroke.”
For now, she says, scientists offer no general recommendations on the ideal amount of tea to drink.
“We wouldn’t recommend people change their tea intake based on this one study alone,” Inoue-Choi said.