Scientists found that a supplement taken by 40 million Americans for joint pain is associated with 25% faster progression to Alzheimer’s in people with early memory decline
More than 40 million Americans take glucosamine every year. Most of them are older adults managing joint pain, people whose knees ache going down stairs and whose doctors or pharmacists suggested this widely available supplement as a safe, natural way to protect cartilage and reduce inflammation. For most of its history as a supplement, glucosamine was considered essentially benign. A study published June 9 in Nature Metabolism by researchers at the University of Florida just changed that picture for a specific population that urgently needs to know about it.
Among people who had already been diagnosed with mild cognitive impairment, a condition that often precedes full Alzheimer’s disease, those who were taking glucosamine were 25 percent more likely to progress to dementia than those who were not. Among people who already had Alzheimer’s disease and related dementias, glucosamine use was associated with a 25 percent higher risk of death. The supplement that millions of older adults take to protect their joints may be accelerating the neurological decline they are most at risk of experiencing.
The Dataset Behind the Finding
The University of Florida research team, led by Ramon Sun, director of the Center for Advanced Spatial Biomolecule Research, and Matt Gentry, chair of biochemistry and molecular biology, used artificial intelligence to analyze anonymized patient health records from the UF Health system collected between 2012 and 2024. The scale of the analysis is significant: 24,000 patients diagnosed with Alzheimer’s disease and related dementias, and 41,000 patients with mild cognitive impairment. Among both groups, approximately 8 percent reported taking glucosamine, representing 1,896 patients with dementia and 2,750 with mild cognitive impairment.
After controlling for age, sex, and demographics, the analysis showed the 25 percent higher likelihood of progression from mild cognitive impairment to full dementia in glucosamine users. The research team then extended the analysis into laboratory work, using advanced spatial imaging technology to scan human brain specimens and genetically modified mouse models of Alzheimer’s disease to identify the biological mechanism that could explain the statistical association.
“A lot of these people are actively taking an over-the-counter supplement that could be making their disease progression worse,” Gentry said.
The Sugar Problem in the Aging Brain
The mechanism the UF researchers uncovered runs through a process called glycosylation, the attachment of sugar molecules to proteins. This is a normal and essential biological process. Proteins require specific sugar attachments to function correctly, to fold into the right shapes, to find their correct locations in cells, and to carry out their assigned tasks.
In a healthy brain, glycosylation is tightly regulated. In an Alzheimer’s brain, the process is dysregulated in a specific and damaging way. The researchers found that Alzheimer’s brains show hyperglycosylation, a state where proteins are receiving far more sugar attachments than they should, disrupting how vital protein machines operate throughout neural tissue. The paper’s title, Hyperglycosylation is a metabolic driver of Alzheimer’s disease, signals that this process is not just a symptom of the disease but an active contributor to it.
Glucosamine is itself a sugar molecule, specifically a sugar amine that is sold over the counter as a remedy for joint pain. When glucosamine supplements are consumed, they enter metabolic pathways that feed into exactly the cellular machinery responsible for protein glycosylation. In the mouse experiments, glucosamine significantly increased the attachment of sugar residues to proteins in brain cells. Deficits in social memory, specifically the memory of recognizing familiar individuals, worsened measurably in glucosamine-treated mice compared to controls.
The chain of logic the UF team is proposing is coherent and grounded in the biology. An Alzheimer’s brain is already struggling with hyperglycosylation. Glucosamine supplements provide additional substrate to the same metabolic pathways driving that hyperglycosylation. The result may be a compounding of the molecular dysfunction that is already accelerating cognitive decline.
The Important Nuance in the Data
The researchers were careful to note something that significantly complicates the picture. Earlier studies have linked glucosamine supplements to a lower dementia risk in cognitively healthy adults. The UF findings do not contradict those reports. They qualify them.
“While glucosamine appears safe and potentially protective for a healthy brain, it may be harmful for a brain that is already experiencing cognitive decline,” the research team wrote. The distinction between a healthy brain and one already showing signs of impairment may be the critical variable that previous research on glucosamine and cognition was not able to separate cleanly. Observational studies in the general population captured the protective signal in healthy adults. The UF analysis, by focusing specifically on patients with existing mild cognitive impairment and dementia diagnoses, isolated the population where the risk appears to concentrate.
This means the finding is targeted rather than universal. Glucosamine users who are cognitively healthy are not the population the research is most urgently addressing. The population that needs to reassess is the one that is already managing early memory concerns, that has received a mild cognitive impairment diagnosis, or that has a significant family history of dementia placing them at elevated personal risk.
The Overlap Nobody Was Monitoring
The reason this finding matters at a population scale is demographic. The people most likely to take glucosamine for joint pain are older adults, because osteoarthritis prevalence increases sharply with age. The people most at risk for mild cognitive impairment and Alzheimer’s disease are also older adults. These two populations are not just overlapping. They are largely the same population.
Of the approximately 7.2 million Americans aged 65 and older currently living with Alzheimer’s disease, a significant proportion are also taking glucosamine. Of the millions more who are managing mild cognitive impairment and sitting at the threshold where progression to full dementia is the primary clinical concern, many are also taking glucosamine. The supplement marketed to the joint health of aging adults has been entering the bodies of people whose brains may be the most vulnerable to its metabolic effects, without any clinical guidance directing them to reassess.
Matt Gentry described the finding as raising an important clinical question that now deserves much more attention. The study is observational, not a randomized controlled trial, meaning it establishes association rather than proven causation. Clinical trials will be needed to confirm the causal direction and establish whether discontinuing glucosamine in patients with existing cognitive impairment actually slows progression. That evidence does not yet exist.
But the biological mechanism is biologically plausible and now supported across multiple levels of evidence: patient records, human brain tissue imaging, and animal models. That convergence across methodologies is what elevates an observational association from statistical noise to a finding that clinicians and patients should take seriously.
What People Taking Glucosamine Should Know
The researchers were explicit about what they are and are not recommending. They are not advising everyone who takes glucosamine to stop immediately. They are identifying a specific risk signal in a specific population that warrants a conversation with a physician. For people who are cognitively healthy, the existing evidence does not point toward harm and may suggest modest protection. For people with mild cognitive impairment, dementia diagnoses, or significant family history of Alzheimer’s disease, the calculus has now changed in a way the research community had not previously identified.
“While it’s an association and not proof of causality, it does raise an important clinical question that now deserves much more attention,” Gentry said. The supplement aisle at every pharmacy in America contains bottles of glucosamine that will be purchased today by older adults who have no idea this question exists. After June 9, 2026, their doctors and pharmacists have data that makes it worth asking.
Sources:
Hawkinson, T.R., Liu, Z., Ribas, R.A., et al. Hyperglycosylation is a metabolic driver of Alzheimer’s disease. Nature Metabolism, June 9, 2026. DOI: 10.1038/s42255-026-01538-4
