They noticed that people who drank hot tea on a daily basis were 74% less likely to develop glaucoma than those who did not drink tea. Glaucoma is a serious eye condition which is triggered by excess fluid pressure build-up inside the eye, leading to the damage of optic nerve.
Several studies in the past has suggested that caffeine may have a positive effect intralocular pressure ( inside the eye), but no study has done a comparative study of all these caffeinated drinks or decaffeinated drinks on glaucoma risk.
The data came from a national U.S. study for adults who had undergone an ophthalmological examination and had completed a detailed nutrition questionnaire.
This is a nationally representative annual survey of around 10,000 people that includes interviews, physical examinations and blood samples, created to gauge the health and nutritional status of United States adults and children.
The 2005-06 NHANES also included eye tests for glaucoma for 1678 participants, among whom 5% (84 adults) were identified with the condition.
Decaffeinated tea and iced tea may have lower levels of polyphenols than hot brewed tea, which is why they may not have been associated with lower glaucoma risk.
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Researchers asked the participants how often and how much they had consumed of caffeinated and decaffeinated drinks, including soft drinks and iced tea, over the past 12 months. The answers retrieved in the questionnaire, were then studied in detail. However, drinking other caffeinated beverages like coffee, iced tea, soft drinks, as well as decaffeinated tea, were found to have no impact at all.
That's when researchers found that drinking hot tea every day had a lower risk of developing the eye condition than those who didn't.
As the study was observational, firm conclusions on the cause and effect can not be drawn.
The study also had other limitations, such as the small number of participants with glaucoma and a lack of detailed information about the timeline of diagnosis.
"Further research is needed to establish the importance of these findings and whether hot tea consumption may play a role in the prevention of glaucoma", the team concludes. To make things even more interesting, there was no change for patients who drank decaffeinated hot tea.
Professor Chris Hammond of King's College London, said: "These results are interesting and add to the increasing consensus that tea contains antioxidants and other compounds that are good for our health". However, in this research, it wasn't the type of tea or its strength that appeared protective, rather the temperature at which it was drunk.