We already know that drinking tea may lower your risk of cognitive decline, heart disease, stroke, and type 2 diabetes.
Now, in a study released Thursday in the British Journal of Ophthalmology, researchers found a strong link between people drinking hot tea daily and lower odds of developing glaucoma. That disease of the eye’s optic nerve affects some 3 million Americans and is a leading cause of blindness.
In the study, researchers from UCLA reviewed extensive health and diet questionnaires from 1,678 men and women who participated in the National Health and Nutrition Examination Survey. Among those who consumed at least one cup of hot tea per day, the odds of having glaucoma were 74 percent lower than those of non-tea drinkers.
“Evidence has shown that the antioxidants in tea are associated with lowered heart disease risk factors and possibly cancer,” says Amy Keating, R.D., a Consumer Reports dietitian. “These new findings might show yet another connection to better health.”
The study was intended to observe connections between caffeinated beverages and glaucoma. Some past research has shown that coffee drinkers have a higher risk of glaucoma, and other research has shown the opposite, according to Anne Coleman, M.D., Ph.D., lead researcher and director of the UCLA Mobile Eye Clinic.
In this recent study, however, there were no links observed between coffee consumption and glaucoma. Hot tea, however, was found to have a potential benefit. (Iced tea, decaffeinated tea, and any kind of soda appeared to have no connection to changing one’s glaucoma risk.)
“We were quite surprised by these findings,” Coleman says. “This could certainly prompt further research into why this connection may exist.”
While this study shows an association between tea drinking and lower glaucoma risk, it does not prove that tea is preventive against the disease.
“There may be other lifestyle factors with these daily tea drinkers that we’re not accounting for here,” Coleman says. And because the questionnaires were self-reported, with participants describing remembered behavior from the prior year, there is no way to guarantee the accuracy of their responses.
How Tea May Help
Tea contains polyphenols, which are antioxidants that can help protect against and repair cell damage. These compounds have been thought to contribute to tea’s other health benefits, and in this paper, the researchers speculate that they may play a role in glaucoma, too.
Coffee also contains polyphenols, but they are different from the types found in tea. This could help explain why coffee did not have the same effect on glaucoma risk, according to Coleman. 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.
It should be noted that this study did not differentiate between types of tea (i.e., black, green, white), or the amount of tea consumed daily. So while the connections between tea and glaucoma are still being explored, drinking a daily cup—even two or three—is certainly a healthy choice.