Tea has been a medicinal tool for thousands of years — perhaps since Chinese emperor Shen Nung is thought to have discovered it in 2737 BC. In the Western world, it became known as a commercial health drink as early as 1657, when baristas at Garraway’s Coffee House in London started selling it.
Now, a recent study suggests that drinking a hot cup of it every day might lower people’s risk for glaucoma, one of the leading causes of blindness in the world.
For the study, scientists worked with a pool of interviews, physical exams, blood samples and other data collected from 10,000 people in the United States between 2005 and 2006. Though it was more than a decade ago, they chose that span of time because the National Health and Nutrition Examination collected data about glaucoma then.
The researchers focused on the 1,678 people who had photos, eye test results and surveys about their beverage drinking habits included in the survey. They found that people who drank hot tea every day had a 74% lower chance of developing glaucoma, and that’s after ruling out other factors such as diabetes or smoking.
However, these links were not found in iced tea, nor in caffeinated nor decaffeinated coffee.
But the findings aren’t perfect: The relationship is correlational, and the survey didn’t ask about the amount of tea, type of tea or the amount of time it took for the tea to brew (which would influence its strength). In other words, scientists did not find a direct cause and effect relationship.
The link between tea and lowered glaucoma risk, however, isn’t unbelievable — tea has shown a number of other measurable benefits for the human body.
“Tea contains antioxidants and anti-inflammatory and neuroprotective chemicals, which have been associated with a lowered risk of serious conditions, including heart disease, cancer, and diabetes,” the study’s release said. “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.”