Millions of Americans taking glucosamine for achy joints may be unknowingly accelerating cognitive decline, according to a sweeping new study from the University of Florida that links the common over-the-counter supplement to worsening dementia risk.
The research, published in Nature Metabolism, examined health records from roughly 4,600 patients and found that those with early-stage cognitive problems who used glucosamine were 25% more likely to develop dementia. The same group also showed a 25% increase in mortality risk among those already diagnosed with Alzheimer's disease or related conditions.
Glucosamine use was surprisingly prevalent in the patient population studied. About 8% of both the early cognitive impairment group and the advanced dementia group reported taking the supplement, reflecting its popularity as a natural remedy for joint health.
The findings do not definitively prove that glucosamine causes dementia and will require confirmation through clinical trials. But they raise urgent questions about a supplement that older adults commonly purchase without a prescription, often unaware of potential neurological risks.
"A lot of these people actively take an over-the-counter supplement that could be making their disease progression worse," said Ramon Sun, a senior researcher on the study and director of the Center for Advanced Spatial Biomolecule Research at UF's McKnight Brain Institute, noting that roughly 7 million Americans are living with Alzheimer's disease.
The team used artificial intelligence to analyze deidentified patient records collected between 2012 and 2024 from UF Health, then drilled into the biological mechanisms that might explain the connection. What emerged was an intricate metabolic pathway previously overlooked in Alzheimer's research.
Glucosamine is a naturally occurring sugar-related molecule that can cross the blood-brain barrier. Once there, it feeds into biochemical processes that build complex sugar structures on proteins. Commercial versions are often derived from shellfish shells or corn.
Using advanced spatial analysis technology developed in Sun's lab, researchers discovered that a specific protein and sugar-tagging pathway becomes excessively active in Alzheimer's brains. This hyperactive system appears to be a genuine driver of disease progression, not simply a byproduct of it.
When researchers tested the theory in genetically modified mice, those given glucosamine showed significantly increased sugar attachment to proteins and worsening deficits in social memory, the ability to recognize and remember other individuals. Critically, when scientists chemically reduced this sugar-tagging activity, memory performance improved.
Human brain tissue samples from the UF Neuromedicine Brain and Tissue Bank revealed that Alzheimer's specimens showed substantially higher levels of sugar attachment to proteins compared with healthy controls, further supporting the hypothesis.
"Proteins are the cell's molecular machines," explained Matt Gentry, chair of UF's Department of Biochemistry and Molecular Biology. "What we found in Alzheimer's is that this sugar-tagging system appears to be overactive. 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."
The discovery points toward a fundamentally new therapeutic avenue. Rather than focusing exclusively on the plaques and tangles that define Alzheimer's pathology, researchers say addressing metabolic dysfunction in the brain could prove to be an important complementary approach.
The work required months of sophisticated analysis. Using AI to parse through thousands of patient records, collaborators Yi Guo and Jiang Bian identified patterns that might otherwise have remained hidden. The team then moved from data to mechanistic proof, testing their hypothesis in animal models and examining actual human brain tissue to verify their findings.
Gentry acknowledged that the electronic health record data represent an association rather than definitive proof of causality. "While it's an association and not proof of causality, it does raise an important clinical question that now deserves much more attention," he said.
Author Jessica Williams: "This isn't a wholesale indictment of glucosamine, but it's a serious enough signal that patients and doctors need to have a conversation before millions keep popping these pills thinking they're harmless."
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