Glucosamine Supplements Tied to Risk of Eye Condition

By Denise Mann
HealthDay Reporter

THURSDAY, May 23 (HealthDay News) — Glucosamine supplements 

that millions of Americans take to help treat hip and knee osteoarthritis 

may have an unexpected side effect: They may increase risk for

 developing glaucoma, a small new study of older adults suggests.

Glaucoma occurs when there is an increase of intraocular pressure 

(IOP) or pressure inside the eye. Left untreated, glaucoma is one 

of the leading causes of blindness.

In the new study of 17 people, whose average age was 76 years, 

11 participants had their eye pressure measured before, during and 

after taking glucosamine supplements. The other six had their eye 

pressure measured while and after they took the supplements.

Overall, pressure inside the eye was higher when participants were 

taking glucosamine, but did return to normal after they stopped taking 

these supplements, the study showed.

“This study shows a reversible effect of these changes, which is 

reassuring,” wrote researchers led by Dr. Ryan Murphy at the 

University of New England College of Osteopathic Medicine in 

Biddeford, Maine. “However, the possibility that permanent damage 

can result from prolonged use of glucosamine supplementation 

is not eliminated. Monitoring IOP in patients choosing to supplement 

with glucosamine may be indicated.”

Exactly how glucosamine supplements could affect pressure inside the

 eye is not fully understood, but several theories exist. For example, 

glucosamine is a precursor for molecules called glycosaminoglycans,

 which may elevate eye pressure.

The findings are published online May 23 as a research letter in 

JAMA Ophthalmology.

The study had some shortcomings. Researchers did not have 

information on the dose or brand of glucosamine used, and they did 

not know how long some participants were taking the supplements.

Duffy MacKay, vice president for scientific and regulatory affairs at

 the Council for Responsible Nutrition, a Washington, D.C.-based

 trade group representing supplement manufacturers, said the findings 

don’t mean that people should stop taking the supplements.

“This research letter raises questions and introduces a hypothesis 

that should be explored further, but the small number of cases

 investigated and the [fact that] researchers did not count capsules or control 

for dose or intake or duration of use of glucosamine provide extremely limited 

evidence of harm,” MacKay said.

“This study should not change consumer habits; however, individuals

 with glaucoma or ocular hypertension who are taking glucosamine 

should let their doctor know so that the appropriate monitoring of 

intraocular pressure measurements can be done to identify any 

changes,” he said.

MacKay concluded: “The good news is that increased IOP was 

reversible. So if you take the product, and your IOP goes up, then you 

can stop taking the product to see if it returns to normal.”

However, previous studies have raised questions about whether 

glucosamine supplements provide any health benefit to consumers. 

A large recent study concluded it had no healing effect on arthritic pain.

The potential relationship between glucosamine and glaucoma is new

to Dr. Scott Fudemberg, a glaucoma surgeon at Wills Eye Institute, 

in Philadelphia. “The mechanism about how people can develop 

glaucoma isn’t completely understood, so how the supplements 

may play a role isn’t completely understood either,” he said.

While the study found an association between taking glucosamine 

and increased eye pressure, it didn’t establish a cause-and-effect 

relationship.

The best thing that anyone can do to preserve their vision is to get

regular eye exams, Fudemberg advised. “Glaucoma can be treated 

with medications, lasers and/or surgery,” he said. “These findings 

pose a question about whether oral glucosamine can raise intraocular 

eye pressure, but it doesn’t provide an answer. More research is 

now needed before any conclusions can be drawn.”