A common health supplement could accelerate the progression of dementia according to new research.

People with Alzheimer’s disease who took the supplement glucosamine were 25% more likely to die within five years than people who didn’t.

Glucosamine is a sugar supplement that’s taken for joint health. More than 40 million Americans take it each year, and it can be bought readily over the counter without a prescription.

Researchers looked at medical records for 65,000 people with either dementia or mild cognitive impairment, which is the clinical name for the early stages of the condition.

In the earliest stages of memory loss, people taking glucosamine were 25% more likely to end up with full Alzheimer’s.

The researchers then conducted experiments with mice to try to understand how glucosamine might negatively affect cognition and drive the progression of dementia.

They found that if they blocked the enzyme that produces sugars like glucosamine in the body, the mice with Alzheimer’s-like cognitive impairment showed better memory.

The researchers believe the sugar may be coating protein and lipid molecules within the brain , causing cells to fail and then die, in turn leading to loss of memory and cognitive function.

Over 7 million Americans aged 65 and over now have Alzheimer’s disease.