Topic summary contributed by volunteer(s): Mimi

Blue-green algae, also known as cyanobacteria, are a type of bacteria that are found in soil, lakes, and oceans all over the world. Like plants, they can use sunlight to grow. Animals and fish ingest cyanobacteria, and then enter our food supply when we consume animals, fish, and shellfish.

Blue-green algae are used in supplements claiming nutritional value and health benefits. However, the potential neurotoxicity of blue-green algae supplements may pose a health concern.

Neurotoxins in Blue-Green Algae

Almost all blue-green algae can produce neurotoxins. One of these neurotoxins is BMAA, an amino acid which increases the risks of degenerative diseases of the central nervous system. BMAA is found throughout the world. Aquatic animals, such as fish and shellfish, contain high concentrations of BMAA.

In fact, researchers found BMAA in the brains of Canadian patients with Alzheimer’s. In 2009, further research through a study done in Miami revealed that BMAA was also found in the brains of Floridians with Alzheimer’s, Lou Gehrig’s disease (ALS), and those dying from Parkinson’s disease. Exposure to BMAA through eating fish and seafood was considered a possible source of the toxin. High levels of BMAA were found in Florida fish and seafood.

Spirulina Safety

Spirulina is a type of blue-green algae. While health claims for spirulina supplements abound, there is cause for concern. These supplements were found to contain liver toxins and neurotoxins. In fact, in 2009, a potent neurotoxin was found in spirulina.

Although the U. S. Pharmacopeia’s safety evaluation of spirulina concludes that “the available evidence does not indicate a serious risk to health or other public health concern when spirulina is properly identified, formulated, and used,” consumers should be advised to choose spirulina supplements with third party testing. Researchers reported a range of adverse reactions but attributed them to other algae toxins within the spirulina.


Chlorella is unicellular freshwater green algae sold as powder or compressed into tablets. It does not have the toxins that may be present in blue-green algae or spirulina supplements. Although some adverse reactions have been reported in sensitive individuals, they were not due to toxins. For the vast majority of people, chlorella can be considered helpful.

Chlorella supplementation may increase immunity. For example, chlorella supplementation appeared to prevent loss in immune function in athletes in training camp who experienced intense physical activity and group living. Athletes given a daily dose of chlorella did not experience a drop in immune function as did those who did not receive it. Another study by the World Journal of Gastroenerology was done to test the efficacy of chlorella supplementation in adults with chronic hepatitis C infection. Researchers found a significant improvement in ALT, a marker of liver inflammation, which could be explained by a beneficial immunostimulatory effect of chlorella supplementation.

For substantiation of any statements of fact from the peer-reviewed medical literature, please see the associated videos below.

5 videos

Subscribe to our free newsletter and receive our Daily Dozen Meal Planning Guide.

Subscribe to our free newsletter and receive our Daily Dozen Meal Planning Guide.

All Videos for Blue-green Algae

Pin It on Pinterest