A widely used over-the-counter dietary supplement often taken by older adults to manage joint discomfort and support joint health has been linked to a potentially concerning outcome in people experiencing early cognitive problems.
Researchers at the University of Florida have found that the use of glucosamine was associated with a greater likelihood that mild cognitive impairment would progress to full dementia. Mild cognitive impairment, frequently referred to as MCI, describes measurable difficulties with memory or thinking that are more pronounced than what would typically be expected with normal aging, though they do not necessarily interfere substantially with an individual’s everyday life or independence.
The striking findings stem from a large, comprehensive retrospective analysis of patient health records, which was further supported by intricate experiments involving human brain tissue samples and mouse models of Alzheimer’s disease. While the results remain preliminary and underscore the necessity of formal testing in a human clinical trial, the research team emphasizes that the data adds to a growing body of scientific evidence suggesting that disrupted metabolic processes may play a critical and underappreciated role in neurodegeneration.
The study was published in the prestigious scientific journal Nature Metabolism.
A Popular Supplement Comes Under Scrutiny
"In the United States, there are about 7 million people living with Alzheimer’s and millions more with related dementias such as Lewy body or frontotemporal dementia," said senior author Ramon Sun, Ph.D., director of the Center for Advanced Spatial Biomolecule Research and associate director for innovation at UF’s McKnight Brain Institute. "A lot of these people actively take an over-the-counter supplement that could be making their disease progression worse."
Glucosamine is widely sold without a prescription in pharmacies and health food stores across the globe, and it is especially popular among older adults who rely on it to alleviate joint discomfort and maintain overall joint health. Because the compound is consumed by millions of people on a regular basis, the researchers wanted to investigate whether it might influence the trajectory of Alzheimer’s disease and related dementias, collectively known as ADRD.
Collaborating with Yi Guo, Ph.D., and Jiang Bian, Ph.D., the research team utilized advanced artificial intelligence methodologies to analyze deidentified patient records from UF Health collected over a twelve-year period from 2012 to 2024.
The investigators centered their analysis on patients who had been formally diagnosed with either ADRD or mild cognitive impairment. Across both clinical groups, 8% of the patients reported using glucosamine as a regular supplement. This cohort included 1,896 individuals living with ADRD and 2,750 people dealing with mild cognitive impairment.
Glucosamine Linked to Dementia Progression
After carefully accounting for confounding variables such as age, sex, and various demographic factors, the researchers discovered that glucosamine use was associated with a 25% higher likelihood that an individual’s mild cognitive impairment would progress to full-scale dementia.
Furthermore, among patients who had already been diagnosed with ADRD, the use of glucosamine was also associated with a 25% higher mortality risk, translating to a greater statistical likelihood of death occurring during a defined follow-up period.
Interestingly, the researchers did not observe this same mortality association within the mild cognitive impairment group. This notable difference suggests that glucosamine may exert a stronger or more dangerous biological effect once dementia has already become established in the brain.
Importantly, the findings derived from electronic health records do not definitively prove that glucosamine itself causes dementia to progress. Observational studies are inherently limited to revealing associations rather than absolute cause-and-effect relationships, meaning that other underlying differences between people who choose to take a supplement and those who do not could potentially contribute to the observed statistical outcomes.
"The electronic health record data are very provocative," said Matt Gentry, Ph.D., chair of UF’s Department of Biochemistry and Molecular Biology and a co-author of the study. "While it’s an association and not proof of causality, it does raise an important clinical question that now deserves much more attention."
A Metabolic Pathway May Help Explain the Link
To move beyond mere statistical association, the researchers also uncovered concrete evidence of a specific biological mechanism that could help explain the link between the supplement and neurodegeneration.
Their ongoing work points directly to a metabolic pathway involving the attachment of complex sugar structures to proteins within cells. This chemical process is a normal, vital part of standard cell biology, but the research team found compelling signs that this exact process becomes excessively and abnormally active in the brains of people with Alzheimer’s disease.
Dr. Sun noted that this abnormal metabolic activity could eventually become a prime target for the development of entirely new therapeutic treatments.
"Our results suggest that altered metabolism is a significant contributor to Alzheimer’s progression and, in addition, addressing the metabolic defect could be an important complement to approaches focused on Alzheimer’s plaques and tangles," Sun said.
Amyloid plaques and tau tangles are two of the most well-known pathological hallmarks of Alzheimer’s disease. Plaques consist of abnormal deposits of a protein called amyloid beta that accumulate in the spaces between brain cells, while tangles are twisted, dysfunctional forms of the tau protein that develop inside neurons. Much of the global research into Alzheimer’s disease has historically focused heavily on these two abnormalities, but scientists are increasingly studying additional cellular processes that may contribute significantly to the disease’s advancement.
Mapping Thousands of Molecules in the Brain
A specialized spatial technology developed directly within Dr. Sun’s laboratory enabled the research team to examine these intricate metabolic changes with an unprecedented level of detail.
"This technology allows us to examine thousands and thousands of molecules created when the body breaks down food or drugs and to uncover intricate pathways that otherwise would stay hidden," Sun explained.
The team then narrowed their focus specifically to examine glucosamine. Glucosamine is a naturally occurring, sugar-related molecule that possesses the chemical ability to cross the blood-brain barrier, which is the highly protective physiological boundary that tightly controls which substances are permitted to move from the bloodstream into sensitive brain tissue.
Once inside the central nervous system, glucosamine is capable of entering biochemical pathways that construct complex sugar structures and subsequently attach them to various cellular proteins. Commercial glucosamine supplements consumed by the public are typically produced from raw materials including shellfish shells or corn.
According to the researchers, the ultimate biological effects of glucosamine may depend heavily on the specific physiological environment in which it is operating. A healthy, young brain and a brain actively damaged by Alzheimer’s disease may therefore respond in drastically different ways to the exact same molecule.
The data indicated that the Alzheimer’s-affected brain appeared to be uniquely and particularly vulnerable to this specific metabolic pathway.
Mouse Experiments Point to a Possible Mechanism
To explore this proposed mechanism much more closely, the scientists turned to studies involving genetically modified mouse models.
In these animal experiments, the administration of glucosamine significantly increased the attachment of sugar residues to proteins inside brain cells. Concurrently, the mice treated with glucosamine developed noticeably worse deficits in social memory—which involves the recognition of other animals—when compared against the control group of animals.
When the researchers utilized a chemical intervention to suppress this sugar-tagging process in the mice, their memory performance subsequently improved.
This controlled experiment strongly suggested that excessive sugar tagging could play a direct functional role in the memory deficits observed in the animals, rather than simply occurring as an unrelated biochemical bystander alongside the disease.
Human Alzheimer’s Brain Tissue Shows the Same Pattern
Following the animal trials, the researchers examined human brain tissue in collaboration with Stefan Prokop, M.D., a neuropathologist at the university.
Brain specimens obtained from individuals who had suffered from Alzheimer’s disease, provided by the UF Neuromedicine Brain and Tissue Bank, displayed significantly higher levels of protein sugar attachment than tissue samples taken from normal, healthy control subjects.
When combined with the earlier mouse experiments and the extensive health record analysis, these findings strongly suggest that abnormal cellular metabolism may be much more than a mere secondary consequence of Alzheimer’s disease. Instead, the researchers reported that it could actively contribute to the underlying disease process itself.
"Proteins are the cell’s molecular machines, and many of them need sugar tags added in just the right way to fold correctly, travel to the right place and do their jobs," Dr. Gentry said. "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 cumulative results raise a potentially vital clinical question regarding the widespread use of glucosamine among individuals who are already experiencing cognitive impairment or dementia. However, researchers stress that the current data does not yet establish that people should immediately stop taking the supplement. A rigorously controlled human clinical trial will ultimately be required to determine definitively whether glucosamine directly accelerates the progression of Alzheimer’s disease and, if so, which specific patient populations may be the most vulnerable.