A study published in the British Journal of Ophthalmology that suggest drinking a cup of hot tea daily could be linked with decreasing the risk of developing glaucoma. Drinking coffee, soft drinks, ice tea, and decaffeinated tea does not appear to make any difference to the risk of developing glaucoma according to the researchers.
Glaucoma is a serious eye condition, it causes intraocular fluid pressure to build up inside the eye damaging the optic nerve. It is estimated that glaucoma affects 57.5 million people. It is estimated that rate of glaucoma will rise to 65.5 million people being affected by 2020. Glaucoma is one of the leading causes of blindness across the globe.
Past studies have suggested that caffeine may alter intraocular pressure, but there were none comparing the potential effects of decaffeinated and caffeinated drinks on the risks of developing glaucoma.
Researchers investigated the data from the National Health and Nutrition Examination Survey which consists of survey results involving 10,000 people which included blood samples, interviews, and physical examinations used to gauge the nutritional and health status of US children and adults. The researchers looked at the results from 2005-2006, in that year eye tests were conducted testing for glaucoma, 1678 participants participants had full eye exams conducted including photos in which 5% of the adults had developed glaucoma.
Participants were questioned on how often, what kind, and how much they had drank of decaffeinated and caffeinated drinks, including iced teas and soft drinks over the preceding year using the Food Frequency validated questionnaire. Compared to those who did not drink hot tea daily the individuals that did data showed that they had lower glaucoma risk. After calculating for influential factors such as smoking and drinking, hot tea drinkers were found to have 74% decreased risk to have glaucoma. Findings showed no such links for coffee, iced tea, soft drinks, or decaffeinated tea.
As this was an observational study no firm conclusions can be made about the cause and effect. Information on when glaucoma was diagnosed was unavailable, and the absolute numbers of participants with glaucoma were small. The survey did not ask factors that may have been influential such as tea type, cup size, or the length of brewing time.
Tea has been shown to contain antioxidants and neuroprotective and anti-inflammatory chemicals which are linked with lower risks of serious conditions such as cancer, diabetes, and heart disease. Studies done in the past suggest the neurodegeneration and oxidation may play roles in the development of glaucoma, according to researchers, who add that further studies are needed.
