Glucosamine, one of the most widely used supplements for joint pain, has been linked to faster progression of memory decline in a new study from University of Florida Health, published in Nature Metabolism. The researchers are careful to say their health-record findings show an association, not proof that glucosamine causes harm, but laboratory experiments suggest a mechanism worth taking seriously.

What the study found

The team used artificial intelligence to analyze de-identified electronic health records from UF Health covering 2012 to 2024. They looked at two groups: 2,750 people with mild cognitive impairment (MCI), an early stage of memory problems, and 1,896 people with Alzheimer’s disease or a related dementia. About 8% of each group reported taking glucosamine.

  • Among people with MCI, glucosamine users were about 25% more likely to progress to dementia.
  • Among people who already had dementia, glucosamine users had about a 25% higher risk of death during follow-up. (That mortality difference was not seen in the MCI group.)

The proposed mechanism: “sugar-tagging”

Glucosamine is an amino sugar, a building block the body uses to attach sugar chains to proteins, a process called glycosylation. Lead researcher Ramon Sun and colleagues have previously found that proteins in Alzheimer’s brains carry excessive sugar tags. Their hypothesis is that extra glucosamine may feed that process.

To test it, they turned to mice. Glucosamine increased protein glycosylation in the brains of Alzheimer’s model mice and worsened their social memory. When the researchers suppressed the glycosylation process, the animals’ performance improved. That does not prove the same thing happens in people, but it gives the health-record finding a biological rationale.

Why this is not proof

The human data are observational, and the authors say explicitly that the results do not show glucosamine itself causes dementia to progress. People who take glucosamine differ from those who don’t in ways that may matter. They are more likely to have osteoarthritis, which is linked to pain, reduced activity, inflammation and use of other medications, all of which could affect brain health. Supplement use is also often poorly recorded in medical charts. The study could adjust for some of these factors, but not all of them. There is also the possibility of reverse causation: people whose health is already declining may be more likely to have their supplements recorded, or to start taking remedies for aches and stiffness, which would make glucosamine look harmful even if it isn’t.

How big is a 25% increase?

A 25% higher risk sounds alarming, but it is a relative figure. Its real-world meaning depends on the starting risk. People with mild cognitive impairment already have an elevated chance of progressing to dementia over the following years; a 25% relative increase on that baseline would be meaningful if it proved causal, but it is not the same as saying a quarter of glucosamine users will develop dementia. Because only 8% of patients took glucosamine, the number of users in the study was also modest, which widens the uncertainty around the estimate.

What we know about glucosamine

Glucosamine is sold over the counter, often combined with chondroitin, for joint pain and osteoarthritis. The evidence that it relieves arthritis pain is mixed at best: some trials show small benefits, many show little or none compared with placebo. Because it is a supplement rather than a drug, it has not had to go through the kind of safety testing required for medicines. That context matters: if a supplement’s benefits are uncertain, even a possible risk deserves attention.

Should people stop taking it?

The researchers stop short of telling people to stop, and call for controlled clinical trials before firm recommendations are made. For people who already have memory problems, it is reasonable to raise glucosamine with a doctor or pharmacist, weighing whether it is actually helping their joints against this new, unproven signal. Anyone with a diagnosis of MCI or dementia should review all their supplements with their care team, since several common products can interact with medicines or affect cognition.

What does lower dementia risk

While the glucosamine question is sorted out, the evidence on what helps is much stronger. The 2024 Lancet Commission on dementia identified 14 modifiable risk factors — including high blood pressure, high LDL cholesterol, physical inactivity, smoking, diabetes, untreated hearing loss and vision loss, social isolation and excess alcohol — and estimated that addressing them could prevent or delay nearly half of dementia cases. None of those involve a supplement. For people worried about memory, they are the best-supported place to start.

What comes next

The logical next steps are to confirm the association in other large health-record and cohort datasets with better data on supplement use, and eventually to test directly whether glucosamine affects brain glycosylation or cognitive decline in people. The research also highlights a broader point: supplements taken for one part of the body can have effects elsewhere, and deserve the same scrutiny as medicines. This is research news, not medical advice. Don’t stop or start any supplement or medication without talking to a healthcare professional.