Tenuous Links Between Blue-green algae and Neurological Diseases

Blue-green algae can produce toxins and pose health risks. Photo by LCC monitor Tim Etchells.

Blue-green algae have been implicated in the development of some neurodegenerative diseases leading to headlines like, “Could tap water cause Lou Gehrig’s Disease?” or “Are toxins in seafood causing ALS, Alzheimer’s and Parkinson’s?It is no surprise that many such headlines end with question marks. There is a great deal of fogginess about any actual connection between the diseases and environmental agents that might cause them. While a relationship may exist, the link is far from certain.

The debate revolves around an amino acid known as beta-methylamino-L-alanine, BMAA for short. Amino acids are the building blocks of proteins; there are 20 of them that the human body can make and then combine in various manners to form the proteins in our bodies. However, there are other amino acids that don’t regularly get incorporated into proteins – BMAA is one of these. If BMAA accidently gets incorporated into proteins then it changes their shape and impairs their function. Researchers found BMAA in the brains of Canadians who had Alzheimer’s, and in the brains of victims of a variety of neurologic conditions in Guam.

BMAA is produced by blue-green algae, but not just blue-green algae in lakes. Blue-green algae are everywhere. They exist in freshwater and saltwater. They form symbiotic relationships with fungi to make lichens and with plants to collect nitrogen from the atmosphere. There are species that live freely in the soil. Almost all (95%) blue-green algae strains tested for BMAA from these varied environments were found to produce it. As a result, everyone is exposed to blue-green algae at some level, but only a small subset develops neurodegenerative diseases.

The Lancet, a leading medical journal, called any link between blue-green algae (also called cyanobacteria) and neurodegenerative diseases “a long-shot”. They quote a number of prominent neuroscientists to support that risk assessment.

  • “It is unclear why BMAA would selectively affect motor neurons, the cells primarily involved in ALS (Lou Gehrig’s Disease). Even if BMAA is present in the brain in low abundance, it may not have any adverse consequences.” - Douglas Galasko - University of California-San Diego Department of Neurosciences
  • “Most of the literature related to BMAA cyanobacteria addresses potential biological sources for exposure to BMAA while ignoring the paucity of evidence that BMAA can induce such progressive ALS-related pathology” - Daniel Perl - Uniformed Services University of Health Sciences in Bethesda, Maryland
  • “We see the BMAA theory as complementary to current genetic research, and are very open to the possibility that other environmental factors may be involved.” - Paul Cox - Institute for Ethnomedicine and leading proponent of the BMAA as causative agent hypothesis.

One real advantage of the research connecting BMAA to neurodegenerative diseases is it opens a line of investigation into potential treatments. Based on the BMAA hypothesis, clinical trials have been approved for two patented drugs. One would prevent BMAA from being incorrectly incorporated into proteins. The other would facilitate the body’s ability to remove BMAA. Either may prove to ameliorate the symptoms of neurodegenerative diseases, but much work remains ahead.

Researchers from Dartmouth Hitchcock Medical Centerproposed the idea that people living closer to lakes might be more susceptible to neurodegenerative diseases. They mapped the locations of ALS patients and found clusters of patients around certain waterbodies. The most substantial cluster appeared around Mascoma Lake in New Hampshire. However, when they searched for BMAA in Mascoma Lake they were unable to find any.

There has not yet been a plausible mechanism proposed that would explain how BMAA could get from blue-green algae into people, but it would likely involve biomagnification. Biomagnification is the tendency for a substance to increase in concentration with each step in the food chain; consumers have more than producers.

In Guam, where the link was first made between BMAA and neurodegenerative diseases, the route of exposure is thought to be from diet. Flour from cycad trees was a staple in the native diet, and BMAA was found in the flour. Natives also ate fruit bats, which fed on cycad seeds. The cycads had a symbiotic relationship with blue-green algae that may have been the original source of BMAA. BMAA has been shown to biomagnify in blue-crabs, sharks, shrimp, bass, and bottom feeding fish.

BMAA may accumulate, but declarations of links between blue-green algae and neurodegenerative diseases are tenuous.

Still, as Tracie Caller, one of the researchers working on the Dartmouth study noted, “Avoiding blooms is a good idea because of other health hazards (not because of fear of ALS).” Even if BMAA has no role in neurodegenerative diseases, we still know blue-green algae produce other substances that have been linked to dog deaths and can cause skin irritation or an upset stomach.

To increase knowledge of where and when blue-green algae blooms, the Lake Champlain Committee trains and oversees a group of volunteer blue-green algae monitors. Each week during the summer monitors check the water in their designated area and report the presence or absence of blooms. Sign up here if you'd like to be trained to distinguish blue-green algae or serve as a monitor during the 2014 season.

Results are shared with state and municipal environmental, health, and recreation agencies and used to populate an on-line map of bloom occurrence maintained by the Vermont Department of Health. Blue-green algae are present in less than 10% of the observations submitted each year, and blooms vary weekly and spatially within a given week.

This vital monitoring network helps inform the public and allows people to direct their activities to areas of the lake with less blue-green algae at any given time.

The takeaway: we recommend avoiding blue-green algae – but caution against exaggerating the health risks they pose.