Glucosamine, an over-the-counter supplement taken by millions of Americans for joint pain, was tied to a 25 percent higher likelihood of progressing from mild cognitive impairment to full Alzheimer's disease, according to a University of Florida Health study published in Nature Metabolism on June 9, 2026. The team analyzed deidentified electronic health records from 2012 to 2024 and identified 4,646 patients with either mild cognitive impairment or an existing dementia diagnosis who reported taking glucosamine, about 8 percent of the monitored cohort.
The finding comes with a crucial caveat. The increased risk appears specific to people whose brains are already changing. Glucosamine "appears safe and potentially protective for a healthy brain," lead researcher Ramon Sun writes, and earlier work in cognitively healthy adults has actually linked the supplement to lower dementia risk.
Among patients already diagnosed with Alzheimer's or another form of dementia, glucosamine use was also associated with a 25 percent higher risk of death within five years. The evidence is observational, and the authors stress that the finding shows association, not proof of cause.
How glucosamine may reach the brain
Glucosamine is a naturally occurring sugar molecule that can cross the blood-brain barrier, the tight cellular gate that normally shields the brain from many circulating compounds. Once inside, it feeds pathways that add sugar chains to proteins, a process called glycosylation.
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In a healthy brain, those sugar tags help cells communicate. In an Alzheimer's brain, the system is already dysregulated, and adding more raw material appears to make things worse. "The Alzheimer's brain is adding too many of these sugar structures, and this seems to contribute to the disease rather than protect against it," said Matt Gentry, chair of the Department of Biochemistry and Molecular Biology at the University of Florida College of Medicine.
The team backed the human data with animal experiments. Blocking the enzyme that produces the sugar chains improved symptoms in mouse models of dementia, while giving glucosamine to Alzheimer's-model mice made memory loss worse. Healthy mice on glucosamine showed no adverse effects.
What it means if you take glucosamine
Glucosamine is one of the most widely used dietary supplements in the United States, mainly for knee and other osteoarthritis pain, although its clinical benefit has long been debated.
Sun, director of the Center for Advanced Spatial Biomolecule Research at UF and the study's senior author, said the worry is that "a lot of these people actively take an over-the-counter supplement" that could be worsening their disease. His co-author Gentry added that "while it's an association and not proof of causality, it does raise an important clinical question."
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The results still need to be tested in a clinical trial. In the meantime, anyone who has been given a diagnosis of mild cognitive impairment or early Alzheimer's, or who cares for someone who has, should talk to their doctor before continuing a glucosamine supplement. For cognitively healthy adults, the current data do not point to a reason for alarm.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.