Huperzine (HOOP-ur-zeen) A, a dietary supplement derived from the Chinese club moss Huperzia serrata, is sparking some interest as a potential treatment for Alzheimer's disease.

Huperzine A acts as a cholinesterase inhibitor — a type of medication that works by improving the levels of neurotransmitters in the brain. Small early studies suggest that huperzine A might improve memory and protect nerve cells, which could slow the cognitive decline associated with Alzheimer's.

Some studies have found evidence that huperzine A might significantly improve cognitive performance in people with Alzheimer's disease. However, a recent systematic review found that the quality of the evidence of huperzine A's effectiveness was low.

Another systematic review found that huperzine A did have a beneficial effect on cognitive function. But, the review noted that the results should be interpreted with caution because of problems with the way the trials were conducted.

In addition, there's a lack of long-term safety data — most studies have lasted three months or less — and many participants in the trials had side effects, including nausea and vomiting. More studies are needed to determine possible benefits and long-term risks of huperzine A.

The Alzheimer's Association recommends not taking huperzine A, especially if you're taking a prescribed cholinesterase inhibitor, such as donepezil (Aricept), rivastigmine (Exelon) or galantamine (Razadyne). Taking both could increase your risk of serious side effects.

Consult your doctor before starting any dietary supplement, including huperzine A.