December 2016 The on-line British Journal of Ophthalmology published a report indicating that “Drinking a cup of hot tea at least once a day may be linked to a significantly lower risk of developing the serious eye condition, glaucoma.” The investigators looked an an American study which yearly, surveys the lifestyle and health status of 10,000 Americans, by means of both physical exams and interviewing.
The researchers looked at the subjects consumption of coffee, tea, and soft drinks, both with caffeine and without caffeine. After sorting through and teasing out the data (I won’t bore you with the numbers here), the investigators determined that the drinking of a cup of hot tea with caffeine daily reduced the risk of developing glaucoma by 74%. In health research 74% is a BIG number. An almost Too-Good-to-be-True number.
So what is it? Why would the caffeinated tea reduce the risk, but not the caffeine in coffee or soda? For that matter, de-caffeinated tea was not a factor in reducing the risk, at least not in this study. The American survey did not delve into types of tea (green tea, black tea,, Oolong tea, Lipton tea), brewing times, size of the cup, etc. The information was general: one cup (or more) daily.
Glaucoma is a progressive, sight threatening eye disease. The common understanding is that it is a disease of high eye pressure, that damages the light sensing neurons of the retina of the eye. The progressive damage to these nerves results in nerve cell death, and subsequent loss in vision. Most therapies are centered on controlling the pressure inside of the eye. But doctors are finding that these therapies are sometimes not enough. Medical research is focusing on other factors that contribute to the progression of glaucoma.
So that brings us back to the role that hot tea may play in reducing the risk of glaucoma. The questionable aspect is the caffeine. Other research has shown that the eye pressure can go up, which is undesirable, when caffeine, in the form of coffee, in ingested. (JGlaucoma) Tea has other beneficial factors, such as antioxidants, anti-inflammatory, and neuro-protective substances. These factors are also essential for good general health. They have been studied as an important nutritional component for heart and vascular health, diabetic control, and cancer prevention. That which is good for the body is good for the eyes.
The researchers conclude that more research needs to be done to sort out the effects of tea on the risk for the development of glaucoma.
See a review of the article by the British medical Journal