Millions of people take glucosamine every day in the hope of reducing joint pain and maintaining mobility as they age.
The supplement has long been marketed as a natural way to support joint health, particularly for people with osteoarthritis.
Because it is sold over the counter and does not require a prescription, many consumers assume it is completely safe.
However, a new study from researchers at the University of Florida suggests that glucosamine may have unexpected effects on the brain. The findings, published in Nature Metabolism, indicate that people taking glucosamine supplements may face a higher risk of progression from mild cognitive impairment to dementia, including Alzheimer’s disease.
The results do not prove that glucosamine causes dementia. However, the study raises important questions that researchers believe deserve much closer investigation.
Alzheimer’s disease is the most common form of dementia and affects millions of people worldwide. The condition gradually destroys memory, thinking abilities, and daily functioning.
It develops slowly over many years and is characterized by the buildup of abnormal proteins in the brain. These protein deposits, known as amyloid plaques and tau tangles, interfere with communication between brain cells and eventually lead to cell death.
Scientists have spent decades searching for factors that contribute to Alzheimer’s disease. While age remains the biggest risk factor, researchers have also explored the roles of genetics, inflammation, cardiovascular health, metabolism, and lifestyle factors.
The new study focused on glucosamine because previous research had shown that the supplement can cross the blood-brain barrier.
This barrier normally protects the brain from potentially harmful substances circulating in the bloodstream. Since glucosamine can enter the brain, researchers wondered whether it might influence biological processes linked to Alzheimer’s disease.
To investigate, the team used artificial intelligence tools to analyze health records from the University of Florida’s health care system between 2012 and 2024. They examined patients diagnosed with mild cognitive impairment, dementia, or Alzheimer’s disease and looked for patterns involving glucosamine use.
The researchers found that about 8 percent of patients with declining cognitive function were taking glucosamine supplements. After analyzing the data, they observed that people taking glucosamine were about 25 percent more likely to progress from mild cognitive impairment to dementia compared with people who were not taking the supplement.
The study also found that patients already diagnosed with Alzheimer’s disease or dementia who took glucosamine had a roughly 25 percent higher risk of death during the study period.
These findings prompted researchers to explore possible biological explanations. Glucosamine is closely related to sugar molecules used throughout the body. One of its roles involves a process known as protein glycosylation, often described as attaching sugar tags to proteins.
Proteins perform most of the important tasks inside cells. For proteins to function properly, they often need these sugar tags added in precise ways. The tags help proteins fold correctly, travel to the right location, and interact with other molecules.
The researchers discovered evidence suggesting that this sugar-tagging system becomes overactive in Alzheimer’s disease. Instead of helping cells function normally, excessive sugar tagging may contribute to harmful biological changes within the brain.
To test this idea, scientists conducted experiments using genetically modified mice. When the mice received glucosamine, researchers observed a significant increase in sugar attachments on proteins within brain cells. These animals also developed memory problems.
Interestingly, when researchers blocked the sugar-tagging process, memory performance improved. This finding suggested that excessive protein sugar modification might contribute directly to cognitive decline.
The team also examined donated human brain tissue from people with Alzheimer’s disease. They found elevated levels of protein sugar modifications in these samples as well, providing additional support for their hypothesis.
Although the findings are concerning, it is important to interpret them carefully. The human portion of the study was observational, meaning researchers identified an association rather than a cause-and-effect relationship.
It remains possible that other factors influenced the results. For example, people taking glucosamine may differ from non-users in ways that were not fully captured by the analysis.
The study’s strengths include the use of a large patient database, supporting laboratory experiments, animal studies, and examination of human brain tissue. Together, these approaches provide a more comprehensive picture than any single method alone.
However, there are also important limitations. Researchers do not yet know whether different doses of glucosamine carry different risks.
They also do not know whether stopping glucosamine would alter disease progression. Additional studies involving diverse populations and prospective clinical trials will be needed before firm conclusions can be reached.
For now, experts are not advising people to panic or immediately stop taking glucosamine. Individuals with concerns, especially those with mild cognitive impairment or a family history of dementia, should discuss the findings with their healthcare providers.
The study highlights how even widely used supplements can have unexpected biological effects. As scientists continue to uncover the complex factors involved in Alzheimer’s disease, research like this may help identify new pathways for prevention and treatment.
While much remains uncertain, the findings suggest that the relationship between metabolism, brain health, and common dietary supplements deserves much closer attention.
If you care about Alzheimer’s disease, please read studies about the protective power of dietary antioxidants against Alzheimer’s, and eating habits linked to higher Alzheimer’s risk.
For more health information, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
