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One Scary Side Effect of Drinking Too Much Caffeine, According to Science

Don't let your love of coffee blind you of its potential pitfalls.
FACT CHECKED BY Cheyenne Buckingham

There are a lot of reasons to exercise moderation when it comes to drinking coffee. Sure, a cup or two may be able to give you the boost you need to get through the workday, and it can even lend some health benefits, but drinking too much can leave you feeling anxious and jittery.

Not to mention, coffee can even give you acid reflux and heartburn. Turns out, it's not just your esophagus that will thank you when you cut back on your coffee consumption—your eyes might too. A new study, which was published in the June issue of the journal Ophthalmology, finds that drinking too much coffee each day can significantly increase your chance of getting glaucoma, especially if you're already at risk of the disease.

RELATED: 14 Side Effects of Drinking Coffee Every Day, According to Dietitians

According to the study, those who have a genetic predisposition to higher eye pressure (a main factor of glaucoma) and drink more than 321 milligrams of caffeine a day (about three cups of coffee), are much more likely to develop glaucoma. In fact, the prevalence of glaucoma was nearly four times as great as those who drank minimal to no caffeine and were in the lowest genetic risk score group. Granted, you likely do not know whether or not you have high intraocular pressure (IOP), so it might be best to take precautions either way.


"I would recommend avoiding consuming large amounts of caffeine if you are a glaucoma sufferer who is not stable on treatment, or someone with a strong family history of glaucoma who would like to potentially lower their risk of developing the disease," the study's co-author Anthony Khawaja, MD, PhD, Associate Professor of Ophthalmology at the University College London (UCL) Institute of Ophthalmology told Eat This, Not That!

Corresponding study author Louis R. Pasquale, MD, FARVO, deputy chair for Ophthalmology Research for the Mount Sinai Health System, added that only those who drink excessive amounts of coffee and who are predisposed to higher IOP are at increased risk. Assuring us that, "Overall, coffee consumption is safe."

In general, experts recommend sticking to under 400 milligrams of caffeine each day anyway, which is between three and five, eight-ounce cups. So, if you have reason to be worried about your glaucoma risk, consider sticking to just two and three cups daily—it'll save you from the other unpleasant side effects as well.

"Given we only saw the association with increased risk among people with the highest amount of consumption, I think that small to moderate consumption is probably reasonable for all in terms of glaucoma risk," says Khawaja.

For more, be sure to check out these One Major Side Effect of Drinking Coffee From a To-Go Cup, According to Experts.

Clara Olshansky
Clara Olshansky (they/she) is a Brooklyn-based writer and comic whose web content has appeared in Food & Wine, Harper’s Magazine, Men's Health, and Reductress. Read more about Clara
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