A widely used, over-the-counter supplement commonly taken by millions of older adults for joint pain and overall joint health has been linked to a potentially concerning outcome in individuals with early cognitive problems. According to a new study conducted by researchers at the University of Florida, the use of glucosamine was found to be associated with a greater likelihood that mild cognitive impairment would progress to full-scale dementia.
Mild cognitive impairment, frequently referred to as MCI, describes measurable problems with memory or thinking capabilities that are noticeably greater than what would typically be expected with normal aging. However, these issues do not necessarily interfere substantially with an individual’s everyday life or independent functioning. The new findings offer a sobering look at how common dietary supplements might interact with underlying neurodegenerative processes, adding fresh urgency to the study of metabolic health in aging brains.
The findings are the result of a large retrospective analysis of patient health records, which was further supported by laboratory experiments involving human brain tissue and advanced mouse models of Alzheimer’s disease. While the results remain preliminary and will ultimately need to be rigorously tested in a human clinical trial, the research team emphasizes that the discovery adds to a growing body of scientific evidence suggesting that disrupted cellular metabolism may play a critical and underappreciated role in neurodegeneration. The comprehensive study was published in the esteemed scientific journal Nature Metabolism.
A Popular Supplement Comes Under Scrutiny
The implications of the study are vast, given the sheer prevalence of neurodegenerative conditions in modern society. "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 of the University of Florida’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, grocery stores, and online marketplaces across the globe. It is especially popular among older adults, many of whom rely on the compound to manage joint discomfort, stiffness, and long-term joint health. Because of how commonly it is consumed on a daily basis, the researchers wanted to understand whether the supplement might inadvertently influence Alzheimer’s disease and related dementias, collectively known as ADRD.
To investigate this pressing public health question, Sun worked alongside colleagues Yi Guo, Ph.D., and Jiang Bian, Ph.D. The multidisciplinary team utilized artificial intelligence tools to analyze deidentified patient records from UF Health, covering a twelve-year collection period from 2012 to 2024.
The researchers specifically focused their analysis on patients who had been formally diagnosed with either ADRD or mild cognitive impairment. Within both patient cohorts, the data revealed that 8% of individuals reported taking glucosamine. This figure included 1,896 people living with ADRD and 2,750 people who had been diagnosed with mild cognitive impairment.
Glucosamine Linked to Dementia Progression
After carefully accounting for confounding variables such as age, sex, and various demographic factors, the research team uncovered a striking correlation. Glucosamine use was found to be associated with a 25% higher likelihood that an individual’s mild cognitive impairment would progress into full dementia.
Furthermore, among patients who had already been diagnosed with ADRD, the use of glucosamine was also associated with a 25% higher mortality risk. This statistic indicates a greater statistical likelihood of death occurring during a defined period of follow-up observation.
Interestingly, the researchers did not observe this mortality association within the mild cognitive impairment group. This notable difference suggests that glucosamine may exert a stronger or more dangerous biological effect once the neurodegenerative disease process of dementia is already fully established in the brain.
Despite these provocative numbers, the study authors stress an important caveat: the health record findings do not definitively prove that glucosamine itself causes dementia to progress. Observational studies of this nature are powerful tools for revealing associations, but other unmeasured differences between people who regularly take a supplement and those who do not could potentially contribute to the observed results.
"The electronic health record data are very provocative," said Matt Gentry, Ph.D., chair of the Department of Biochemistry and Molecular Biology at the University of Florida 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 from the medical and scientific communities."
A Metabolic Pathway May Help Explain the Link
Moving beyond epidemiological data, the researchers also uncovered concrete evidence of a specific biological mechanism that could help explain the statistical association observed in the patient records.
Their laboratory work points directly to a metabolic pathway involving the attachment of sugar structures to proteins within cells. This biochemical process, known as glycosylation, is a completely normal and vital part of everyday cell biology. However, the researchers found alarming signs that this specific process becomes excessively and abnormally active in the brains of people with Alzheimer’s disease.
Dr. Sun noted that this abnormal hyperactivity within the metabolic pathway could eventually become a primary 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 explained.
For decades, traditional Alzheimer’s research has focused heavily on plaques and tangles, which are two of the most well-known pathological hallmarks of the disease. Plaques consist of abnormal deposits of a protein called amyloid-beta that accumulate in the spaces between brain cells, while tangles are twisted, malfunctioning forms of the tau protein that develop deep inside neurons. While these features remain central to the disease, scientists are increasingly studying additional cellular processes that may contribute to the relentless progression of neurodegeneration.
Mapping Thousands of Molecules in the Brain
To examine these complex metabolic changes in much greater detail, the research team relied on an advanced spatial technology developed directly within Sun’s laboratory.
"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 said.
With this high-resolution analytical capability, the team focused their investigative lens specifically on glucosamine. Glucosamine is a naturally occurring, sugar-related molecule that possesses the unique ability to cross the blood-brain barrier—the highly selective, protective boundary that tightly controls which circulating substances are permitted to move from the bloodstream into delicate brain tissue.
Once it successfully passes into the brain, glucosamine can readily enter biochemical pathways that construct complex sugar structures and attach them to cellular proteins. Commercial glucosamine supplements found on store shelves are typically produced from various organic materials, including shellfish shells or corn.
According to the researchers, the ultimate biological effects of glucosamine may depend heavily on the specific environment in which it is operating. A healthy, young brain and a brain actively damaged and inflamed by Alzheimer’s disease may therefore respond in drastically different ways to the exact same molecule. The data suggests that the Alzheimer’s brain appears to be uniquely and particularly vulnerable to this specific metabolic pathway.
Mouse Experiments Point to a Possible Mechanism
To explore the underlying mechanism more closely and test causality in a living biological system, the scientists conducted experiments utilizing genetically modified mice.
When administered glucosamine, the modified mice exhibited a significant increase in the attachment of sugar residues to proteins inside their cells. Simultaneously, the glucosamine-treated animals developed demonstrably worse deficits in "social memory"—which measures recognition memory—compared to the control animals in the study.
To test whether this sugar-tagging process was truly driving the memory loss, the researchers utilized a chemical treatment designed to suppress the sugar attachment process. Following this intervention, the memory performance of the animals notably improved.
This controlled experiment strongly suggested that excessive sugar tagging could play a direct role in the cognitive and memory problems observed in the animals, rather than simply occurring as a harmless bystander alongside the disease.
Human Alzheimer’s Brain Tissue Shows the Same Pattern
Seeking to confirm whether these animal findings translated to human pathology, the researchers next examined human brain tissue in collaboration with Stefan Prokop, M.D.
Brain specimens obtained from individuals who had suffered from Alzheimer’s disease, generously provided by the University of Florida Neuromedicine Brain and Tissue Bank, displayed significantly higher levels of sugar attachment compared to control tissue taken from individuals who died without the disease.
When combined with the results from the mouse experiments and the extensive health record analysis, these findings strongly suggest that abnormal metabolism is far more than just a secondary consequence of Alzheimer’s disease. Instead, the data indicates that it could actively contribute to the 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," Gentry noted. "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."
Ultimately, the results raise a potentially vital question regarding the routine use of glucosamine supplements among people who are already experiencing cognitive impairment or clinical dementia. However, the researchers emphasize that the findings do not yet establish definitive proof that people should immediately stop taking the supplement. A comprehensive, controlled human clinical trial will be strictly required to determine whether glucosamine directly accelerates the progression of Alzheimer’s disease and, if so, which specific patient populations are most vulnerable to its effects.
