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Cyanobacteria Toxin May Cause Dementia


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

804 Cyanobacteria Toxin May Cause Dementia
A blue-green algae outbreak in Lake Taihu, China, may contribute to neurodegeneration in people living nearby. Jixin YU/Shutterstock

A chemical produced by blue-green algae has been found to cause biological markers associated with Alzheimer's disease in vervet monkeys. The discovery strengthens a suspicion that the toxin β-N-methylamino-L-alanine (BMAA) is contributing to the dementia crisis. In better news, the same study added to evidence for the amino acid L-serine's protective potential.

In the 1950s, the Chamorro people of Guam suffered an outbreak of dementia, along with neurofibrillary tangles in their brains, that resemble those seen in Alzheimer's sufferers. Evidence has since emerged that these symptoms were triggered by exposure to the chemical BMAA found in cycad seeds.


Cycad seeds are not a big global food source, but the BMAA came from cyanobacteria, also known as blue-green algae in the cycads' roots. Cyanobacteria, ancient single-celled organisms, inhabit oceans and deserts, and many produce BMAA in large quantities. A survey of the supposed health food spirulina found BMAA in 14 of 39 samples.

A team led by Dr. Paul Cox of the Institute of Ethnomedicine, Wyoming, gave fruit laced with BMAA to vervet monkeys for 140 days. In the Proceedings of the Royal Society B Cox reports monkeys on the BMAA diet were subsequently found to have higher concentrations of both tau protein tangles and β-amyloid plaque-like deposits in their brains than a control group of monkeys.

Perhaps more importantly, when monkeys were given both BMAA and L-serine there was a 50 percent reduction in the presence of these tangles in some brain regions, and at least 35 percent in others. L-serine and BMAA have such similar structures that cells sometimes treat them interchangeably, even though one is used to synthesize vital proteins and the other is a poison. L-serine has been shown to prevent BMAA damage in cell cultures, but this is the first time a benefit has been shown in living animals. The paper acknowledges the protective mechanism of L-serine is unclear, but raises “prevention of BMAA misincorporation in specific proteins” as one possibility.

“We have sponsored FDA-approved human clinical trials to determine if L-serine is a safe and efficacious treatment to reduce disease progression in ALS [Amyotrophic Lateral Sclerosis, also known as Motor Neuron Disease] patients,” the paper reports. “We hope to initiate human clinical trials of L-serine for mild cognitive impairment and early onset AD [Alzheimer's Disease] in the near future.”


The affected monkeys showed few signs of dementia, but the authors note that β-amyloid plaques occur in the brains of people who were not yet showing signs of dementia at their death, and the same was true of some Chamorro patients.

Cyanobacteria sit at the base of many food chains, raising the danger of BMAA bioaccumulating to dangerous levels. High concentrations have been found in shark fins, providing another reason to avoid shark fin soup.

The combination of excessive nutrient runoff into freshwater systems and more widespread droughts has seen blue-green algal blooms become more common, suggesting we are poisoning our minds as we overload the planet.


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  • dementia,

  • cyanobacteria,

  • Alzheimer's causes