One to remember but more research needed


DOES IT WORK?Huperzia moss could be developed by pharmaceutical companies to help Alzheimer’s patients, writes DÓNAL O'MATHÚNA.

ALZHEIMER’S DISEASE is the most common cause of dementia in older people. It already affects millions of people around the world, and its incidence is predicted to double or triple in the coming decades.

No cure exists and treatment is mostly limited to drugs that delay the decline in memory and mental capacity. The precise cause of the disease is unclear, but levels of a neurotransmitter called acetylcholine appear to be involved. Pharmaceuticals called cholinesterase inhibitors (ChEIs) can temporarily slow the progression of the disease in some Alzheimer’s patients.

The search for new treatments includes herbal remedies. Huperzine A is believed to have much potential, and is already being marketed widely as a ‘memory enhancer’. The compound is found in a moss that grows in China and has been used to make a herbal tea. The moss is called huperzia serrata, or sometimes lycopodium serratum. The tea has been used for centuries in China, though not to treat any form of dementia. Animal studies revealed that huperzine A acts as a ChEI, which has led to its investigation as a treatment for Alzheimer’s disease.

Evidence from studies

The Chinese Cochrane Centre published a systematic review of research on huperzine A in 2008. Six clinical trials were located, all conducted in China. Compared with placebos, huperzine A significantly improved cognitive function when it was measured using a number of tests. However, the reviewers concluded that most trials were of a relatively low quality. No studies measured the impact of the treatment on Alzheimer’s patients’ overall quality of life. Most of the studies lasted only several weeks, although one was conducted for three years. Given the extended duration of Alzheimer’s disease, long-term studies are needed.

Huperzine A is approved for use in China to treat Alzheimer’s disease. It is available in the West as a dietary supplement, which has raised concerns about product quality. One study has been completed in the US, but it did not involve a control group, participants knew what they were taking and the results were not analysed statistically. A randomised controlled trial is under way in the US, funded by the National Institute on Aging.

Another Cochrane review of huperzine A has been published for its use in treating a related condition called vascular dementia. This found no evidence of benefit, although only one small controlled trial was found.

Problematic aspects

Most clinical trials have reported mild gastrointestinal side effects from huperzine A. Pharmaceutical ChEIs can lead to nausea, vomiting, diarrhoea and slurred speech. A number of plants closely related to huperzia and lycopodium species cause toxicity with symptoms matching those of the ChEI drugs. So it is likely that huperzine A may lead to these adverse effects in some people.


The available evidence suggests that huperzine A is similar in effectiveness to currently available drugs for Alzheimer’s disease and may have milder side effects.

However, only a small amount of research is available, and most studies have been of poor quality. Nevertheless, huperzine A has much potential, but possibly not as a treatment itself.

Researchers in Spain have chemically modified huperzine A to produce what is called huprine X.

This is reported to be hundreds of times more active than huperzine A and other pharmaceutical ChEIs.

Almost half the pharmaceuticals on the market today were originally discovered in nature and then modified to make drugs that are more effective and safer.

While there remains a place for using some herbal remedies, huperzine A appears to have most potential as a step along the way to more effective drugs. This does not take away from the contribution of huperzia, but suggests that we may have to wait for the optimum derivative of the natural compound to be developed.

Time is also needed to determine the optimum dose of these compounds and examine their long-term effects. Meanwhile, caution is needed in choosing products as those marketed as dietary supplements may not have been produced to the rigorous standards required of pharmaceuticals.

Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He authored Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007