- The daily cuppa might be the one of best things for your eyes, especially in reducing your chance of going blind.
- One cup of tea at least appears to reduce your risk of developing glaucoma by 74 per cent.
A new study suggests just one cup of tea is associated with lower levels of glaucoma. The study cannot say categorically whether it lowers the risk of developing this eye condition however.
The eye condition blights the sight of many people throughout the world. It is a result of high ocular pressure produced by excess fluid building up inside the eyeball. The optic nerve is damaged as a result of this excessive pressure producing permanent blindness.
Glaucoma affects 57.5 million people worldwide and will increase to 65.5 million by 2020 according to projections. We know it affects 500 thousand people in the UK. The incidence of glaucoma rises with age but can begin from birth. It is a condition that badly affects diabetics in particular.
The findings come from examination of medical data collected from the 2005-2006 National Health and Nutrition Examination Survey (NHANES) in the USA. Much of the evidence is collected from questionnaires about drinking habits and the presence of eye conditions. An immediate caveat – the study was self-reporting so such findings can be prone to error and there were some findings which could be purely generated by random. Even so, the data threw up some interesting correlations.
The researchers looked at the results of eye examinations from 1,678 participants aged 40 or over. There were 84 participants who had glaucoma. The condition of glaucoma was also less in these consuming more than six cups of tea per week even when other factors such as age, body mass index (BMI), smoking and diabetes were taken into account. Those people with glaucoma and diabetes were more common than those with glaucoma and smoking.
The essential finding states that if we drink at least one cup of tea per day, we reduce the risk of developing glaucoma by 74 per cent. Put another way, the chance of having glaucoma, when compared with not having it was 74% lower among those who drank hot tea in such quantities.
The study was published in the British Journal Of Opthamology.
What is also extremely interesting are the findings that other beverages do not appear to influence the risk of glaucoma. So, drinking iced tea, soft drinks, decaffeinated or caffeinated coffee and most intriguing decaffeinated tea do not have the same effect as presumably caffeinated tea. There is also a question mark raised about whether the tea needed to be hot which on examination of the paper may not have been examined as effectively as it might have been.
Some other aspects to consider: possible errors in diagnosis of glaucoma, and the fact that very few participants had glaucoma – and very few of them drank hot tea.
Previous research from a variety of studies indicated caffeine was one of the agents that had a benefit on reducing intraocular pressure. No study however had yet compared caffeinated drinks with decaffeinated types on the risk of glaucoma. It also appears that milk reduces the benefit from the tea.
Glaucoma risk is doubled by long-term use of the contraceptive pill. ( I know it hasn’t anything to do with tea but the finding was also made).
The mechanism needs some explanation, but it is more than likely that components in the tea leaf may be responsible for this benefit. Tea contains a variety of components such as tannins, flavonoids, catechins, especially epigallocatechins, various polyphenols etc. which might protect the nerves from damage or help with drainage of the intraocular fluid so reducing pressure to some extent. All these components have some antioxidant activity. Adding milk is well known to bind the tannins which indicates there presence as free agents in important in this situation. Incidentally, caffeine is an antioxidant too.
There is no direct proof of tea protecting against the condition, just this strong but significant association.
“Tea drinkers should feel comfortable about drinking tea but should realise that the results are preliminary and drinking tea may not prevent glaucoma,” stated Anne Coleman, co-author of the research from the University of California, Los Angeles.
The UK’s Royal College of Ophthalmologists always recommend regular eye tests to check the health of your eyes.
What would be interesting is establishing just which components have the benefit, are some teas better than others and whether caffeine really does have a role here. There are many other questions to be answered which are associated with the actual statistics of the study and the use of self-reporting. Would other types of tea be of benefit ? Is it only black tea that has a role here ? Did the tea drinkers consume different types of tea and at what time of day ? Even so, it adds extra weight to other pieces of research about the benefits of tea consumption. There are also strong associations about ensuring we have enough vitamin B3 because this too, is associated with a reduced risk of glaucoma.
Please refer to the paper:
http://bjo.bmj.com/content/early/2017/11/25/bjophthalmol-2017-310924
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