"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 answ
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