Too much coffee triples the risk of blinding eye disease. How much is too much?

For centuries, workers worldwide have treated coffee like a morning battery charge, drinking a cup or three to wake up and be productive. Many studies suggest that coffee has great health benefits. So it’s surprising to hear, in a new study published in the Ophthalmology Journal, that overconsumption is a serious concern.

According to the authors, daily intake of more than 480 milligrams of caffeine (which roughly translates to four cups of coffee a day,  10 cans of soda, or two energy drinks) can more than triple the risk of developing glaucoma for those genetically disposed to the disease. Increased eye pressure is another possible symptom.

Many doctors recommend that adults limit their daily caffeine intake to between three and five eight-ounce cups of coffee per day. Drink more than this and you increase their chances of developing high blood pressure, an irregular heartbeat, insomnia, muscle atrophy, digestive issues, and anxiety.

What is Glaucoma?

Glaucoma describes a group of eye conditions that damage the optic nerve by inflicting excessive amounts of pressure on them. It seems excessive amounts of coffee inflicted some degree of pressure on all cohorts studied in the new report, even if only those with the most risk endured sight damage.

Glaucoma is the second leading cause of blindness. It is common in the US; more than 200,000 Americans are newly diagnosed every year. Moreover, roughly 50% of patients go a long time without being properly diagnosed.

Populations most at risk for glaucoma often don’t show any symptoms initially. The only way to assess your risk is by having a medical professional analyze your IOP or intraocular pressure (the amount of fluid pressure inside your eye).

“Glaucoma patients often ask if they can help to protect their sight through lifestyle changes, however, this has been a relatively understudied area until now,” says study co-author Anthony Khawaja, MD, PhD, from the University College London Institute of Ophthalmology. Anyone with a high genetic risk for glaucoma “may benefit from moderating their caffeine intake,” he continued.

How much caffeine is too much?

Caffeine values that exceeded 321 milligrams a day were associated with a 3.9-fold higher glaucoma prevalence when compared to those who drink no or minimal caffeine and belonged to the lowest genetic risk score group.

“The UK Biobank study is helping us to learn more than ever before about how our genes affect our glaucoma risk and the role that our behaviors and environment could play. We look forward to continuing to expand our knowledge in this area,” the authors concluded.