Coffee
Kantonsspital St Gallen researchers find that coffee helps to speed up bowel function after colon or bowel surgery. Flickr via Creative Commons

People who regularly consume too much coffee run a higher risk of vision loss, according to new research.

Researchers from the Channing Division of Network Medicine at Brigham and Women's Hospital in Boston, Mass, say that coffee drinkers should limit their intake to reduce their chances of developing vision loss or blindness. They found that heavy caffeinated coffee consumption is associated with increased risk of developing exfoliation glaucoma.

Glaucoma is an eye disease that damages the optic nerve and impairs vision, according to the Princeton education website.

The Boston researchers analysed data on 78,977 women from the Nurses' Health Study (NHS) and 41,202 men from the Health Professionals Follow-up Study (HPFS).

During a 1980 study, they examined the health of the women and men, average age 40, who did not have glaucoma and reported undergoing eye examinations in 1980.

The participants filled in a questionnaire about their coffee consumption.

Two decades later, the participants were invited to take eye examinations, to assess the effects of coffee on their health.

Participants who drank three or more cups of caffeinated coffee daily showed a higher incidence of glaucoma.

The researchers found no links with consumption of other products, such as soda, tea or chocolate.

"Scandinavian populations have the highest frequencies of glaucoma because Scandinavian populations also have the highest consumption of caffeinated coffee in the world," said Jae Hee Kang, one of the researchers.

Previously, researchers found that greater caffeinated coffee intake was associated with increased risk of primary open-angle glaucoma. Now they have found excessive coffee intake increases the risk of developing vision loss.

"Because this is the first study to evaluate the association between caffeinated coffee and exfoliation glaucoma in a US population, confirmation of these results in other populations would be needed to lend more credence to the possibility that caffeinated coffee might be a modifiable risk factor for glaucoma," said Kang. "It may also lead to research into other dietary or lifestyle factors as risk factors."