If you're a tea-lover and have at least one cup a day, you might wanna put your reading glasses on for this. A new study published in the British Journal of Ophthalmology indicates that there may be a link between drinking a cup of hot tea every day and a lower risk of certain eye issues — and that lowered risk isn't found in people who drink coffee, decaf, soft drinks, iced tea or any other kind of beverage. Strike one for the tea-drinkers in the room.
The eye problem, it turns out, that tea may help is called glaucoma. Glaucoma is a vision problem that involves damage to the optic nerve at the back of the brain, and usually turns up in people who are elderly. But it's something that women in particular need to look out for; women experience glaucoma more than men, and we're still not entirely sure why. There are a lot of different factors that can contribute to the development of glaucoma and might affect this gender split, but the potential for tea drinking to be a good eyesight habit is a new theory, and there isn't really a viable explanation for the findings, at least not one that's been tested.
The scientists behind the new study looked at 1678 people, 53.2 percent of whom were white, and tracked both their daily consumption of beverages and how many of them had developed glaucoma. Drinking hot, caffeinated tea daily, the study found, was linked with a 74 percent decreased likelihood of developing glaucoma — but it had to be both hot and caffeinated, because iced tea and decaf tea had no apparent effect whatsoever. And that's pretty mystifying. What is it about hot tea that might be preventing people from developing an eye issue in old age?
The scientists themselves think it might be something to do with both caffeine (which has been shown to increase eye pressure, something that should raise the likelihood of glaucoma) and the antioxidant and anti-inflammatory properties of tea, particularly green tea. But all they've done so far is proven that there might be a link — and it may be that tea-drinkers make other lifestyle choices that mean they're less likely to get glaucoma (perhaps they don't smoke as much, for instance).
So why does this matter for women in particular? Because glaucoma affects us disproportionately — and part of that may have to do with reproductive hormones, particularly estrogen. Research in 2013 indicated that exposure to oral contraceptives meant that glaucoma risk went up in women, and in 2016 a scientific review of 43 different studies of glaucoma in women found that a host of factors about our menstruation, contraception and menopause seem to affect our eye health. If you start your period late in life, take oral contraceptives for longer than 5 years, have a bilateral oophorectomy (ovary removal) before the age of 43, or have early menopause, you're more at risk of developing glaucoma. The key factor in all of them? Estrogen.
The current thinking is that the less exposure you get to estrogen over your lifetime, the more likely you are to get glaucoma; estrogen seems to do some kind of protection when it comes to your eye nerves. Taking oral contraceptives, particularly if they're progestin-only, seems to interfere with the body's estrogen production in ways that influence glaucoma.
And that might have a link to this tea discovery, at least in women. We don't know how many of the patients in the new study were women, but a study in 2017 found that drinking tea causes shifts in how the body's genes turn on and off, including genes that govern how the body metabolizes estrogen. Knowing what we know about estrogen and eyesight, that seems like a plausible link to make. As for why the tea has to be hot to make a difference, though, your guess is as good as mine.
It's a puzzle with many different pieces, but there seems to be a possible relationship between tea, your eyesight, and your hormones, and that could have very big consequences for your life as an elderly lady. Time to break out the teabags.