For years, glucosamine has sat quietly on pharmacy shelves as the go-to tablet for stiff knees and aching hips. Now it is at the centre of a health debate nobody saw coming. A new study from the United States suggests the supplement may be linked to a faster slide into dementia in people whose memory is already failing.
Before anyone tips their bottle into the bin, the details matter. Here is what the research found, what it did not prove, and what it means if you or a relative takes glucosamine.
What the glucosamine study found
The findings were published on June 9 in Nature Metabolism, and they come from researchers at the University of Florida. The team combined a large analysis of patient health records with advanced imaging of human brain tissue and experiments in mouse models of Alzheimer’s disease.
The health-record part of the work drew on the University of Florida Health System’s electronic medical records from 2012 to 2024, from which researchers identified more than 24,400 people with Alzheimer’s and other dementias. A separate group of patients with mild cognitive impairment, or MCI, was also examined. That group numbered about 41,000 people, and the researchers compared those who took glucosamine with those who did not.
MCI is the stage between normal ageing and dementia. People with it show memory or thinking problems beyond what is expected for their age, but their daily lives are not necessarily badly affected.
Two results stood out:
- Faster progression from MCI: After adjusting for age, sex and demographics, glucosamine use was linked to a 25% higher likelihood of moving from mild cognitive impairment to dementia.
- Higher risk of death in established dementia: Among patients already diagnosed with Alzheimer’s disease or a related dementia, glucosamine use was associated with a 25% increase in mortality risk. No such effect appeared in the MCI group. The mortality finding applied to people with dementia who had used glucosamine for at least a year, and it was measured over 10 years.
Why might glucosamine affect the brain?
The lab work offers a possible explanation. Glucosamine is a sugar molecule, and the researchers focused on a process in which cells attach sugar tags to proteins. They found higher levels of this sugar tagging in the brains of people with dementia, and in mice bred to develop dementia, than in healthy brains.
The mouse experiments pushed the idea further. Glucosamine sharply increased the attachment of sugar residues to proteins in the animals’ cells, and their social memory got worse. When the scientists chemically blocked that process, memory improved.
Co-author Matt Gentry, who chairs biochemistry and molecular biology at the university, said the supplement’s effect may depend on context. In his view, the Alzheimer’s brain appears more vulnerable to this metabolic pathway than a healthy one. In plain terms, a supplement that is harmless, or even helpful, in one brain could behave differently in another.
Does glucosamine cause dementia? Not proven
This is the point that gets lost in headlines. The health-record results do not show that glucosamine itself makes dementia progress faster. Observational studies can reveal associations, but other differences between people who take a supplement and those who do not may explain the results.
Consider who takes glucosamine in the first place. Older adults with joint pain are the typical users, and they may differ from non-users in health, mobility and activity levels in ways that no statistical adjustment fully captures. Health and activity levels may play a role, and the findings do not prove cause.
The researchers themselves are cautious. They describe the results as preliminary and say a human clinical trial is needed to test them. Gentry called the record data provocative, but he stressed that an association is not proof of causality and that it raises a clinical question deserving far more attention.
A separate, early analysis posted to the medRxiv preprint server in July adds another note of caution. It asks whether documented glucosamine use in health records truly identifies a glucosamine-specific effect at all. That paper has not been peer-reviewed, so it should be read as a challenge to the original work rather than a rebuttal.
Earlier research told a different story
What makes this story confusing is that earlier studies pointed the other way. One large UK Biobank analysis followed people who were free of dementia at the start. It found that glucosamine users had a lower risk of all-cause dementia, with a hazard ratio of 0.84. Another UK Biobank study reported a lower dementia risk among habitual users, with a hazard ratio of 0.87, which the authors said might be partly explained by type 2 diabetes. Those authors still called for randomised trials.
Some earlier research linked glucosamine to a lower risk of vascular dementia, while other studies found no link with dementia at all.
The Florida team says the two bodies of work need not clash. Lead researcher writing in The Conversation argued that the new findings qualify the earlier reports rather than contradict them: glucosamine may be safe and even protective for a healthy brain, yet harmful for one already in cognitive decline. The earlier studies looked at people without dementia. The new one looked at people who already had memory problems. They were asking different questions.
Why so many people should pay attention
Glucosamine is not a niche product. People spent more than $2.5 billion on it in 2025, and as many as one in four older Americans take it for joint pain. The researchers put the number of Americans using it each year at more than 40 million. Osteoarthritis, the usual reason for taking it, affects about 33 million US adults. The supplement is also easy to find in pharmacies and stores in many countries, Nigeria included, often without a prescription and often without a doctor ever hearing about it.
The dementia burden is large too. Alzheimer’s disease and other dementias affect more than 7 million people in the United States alone.
What should you do if you take glucosamine?
There is no official warning, no recall and no change in medical guidance so far. Based on what the study authors and outside experts have said, a sensible approach looks like this:
- Do not panic or stop abruptly on the strength of one study: The evidence is associational and awaits a clinical trial.
- Tell your doctor or pharmacist, especially if you or a family member has been diagnosed with mild cognitive impairment or any form of dementia.
- Raise it at your next review if you are an older adult who takes glucosamine daily for joint pain. Your doctor can weigh the benefit you get against the uncertainty.
- Ask about other ways to manage joint pain, such as exercise, physiotherapy and weight management, which come with their own benefits.
The bottom line on glucosamine and Alzheimer’s
The Florida study does not say glucosamine causes Alzheimer’s, and it does not say the supplement is dangerous for everyone. It says something narrower and more interesting: in people whose brains are already under strain, a common supplement may not be as harmless as assumed. The researchers also suggest that the overactive sugar-tagging pathway could become a new target for treatment alongside approaches aimed at plaques and tangles.
Until a proper clinical trial settles the question, the honest answer to the headline is “possibly, for some people, but nobody knows yet.” If you take glucosamine, that is a good reason to have a quick conversation with your doctor rather than a reason to worry.
