A popular joint pain supplement taken by millions may be linked to faster cognitive decline and increased mortality in Alzheimer's patients, according to a study published in Nature Metabolism. Researchers found that Alzheimer's patients who took glucosamine were 25% more likely to die within five years compared to those who did not take the supplement.
Study Details and Findings
The study also suggested that people with mild cognitive impairment — often considered an early stage of dementia — were more likely to progress to full Alzheimer's disease if they used glucosamine. Experiments on mice with Alzheimer's-like symptoms produced similar results, with animals given glucosamine showing poorer memory performance.
Glucosamine is a compound made of glucose and the amino acid glutamine, commonly used to slow cartilage breakdown in joints. Over 40 million people in the US take it annually for joint pain relief.
Mechanism: Hyperglycosylation
The researchers highlighted a lesser-known feature of Alzheimer's: an excessive buildup of sugar coatings on brain cells and proteins, known as hyperglycosylation. Under normal circumstances, brain cells carry short sugar chains called N-glycans that help cells communicate. In Alzheimer's patients, these sugar chains accumulate in the wrong places, disrupting protein function and contributing to memory loss and brain cell death. Glucosamine may contribute to this process.
Scientists also discovered that blocking the enzyme responsible for producing sugars like glucosamine appeared to improve dementia symptoms, including short-term memory loss. One key feature of Alzheimer's is the buildup of toxic tau protein clumps in the brain, which interfere with cognitive function.
Conflicting Evidence and Expert Caution
Previous studies have suggested that regular glucosamine use may be associated with a lower risk of dementia in otherwise healthy adults. The new findings, based on patient records, only identify a link rather than proving causation. Integrative medicine physician Dr. Jacob Teitelbaum urged caution: "This does not mean that glucosamine caused the increased risk of dementia. In my opinion, the conclusion of the study is unsound because patients with arthritis commonly exhibit cognitive decline over time. It is far more likely that the chronic arthritis pain caused the increased dementia, NOT the glucosamine."
Dr. Teitelbaum also pointed to research showing a 15% to 39% lower risk of death from all causes among regular glucosamine users. He added: "Increased risk of dementia is especially prominent in arthritis pain. Effectively treating pain is a critical part of decreasing Alzheimer's risk."
Future Research and Implications
Researchers are now investigating compounds that block N-glycan molecules to reduce sugar buildup on brain cells, potentially slowing Alzheimer's progression. Separate studies have suggested that diets high in sugar and saturated fat may contribute to brain inflammation, increasing dementia risk by damaging brain cells over time.
Around 42% of Americans are expected to develop dementia at age 55 or older, a figure comparable to the number of older adults living with arthritis. Many turn to glucosamine for joint pain management, but the new study raises questions about its long-term safety for brain health.
