Is Spirulina Safe?

Given the emerging research on blue-green algae and neurological diseases like ALS, Parkinson’s, and Alzheimer’s, are spirulina foods and supplements safe?

– March 11, 2018

No. To my mind spirulina never has been safe. I have been warning against it for years, and the finding that a neurotoxin found in some spirulina may be related to neurological diseases is the main reason to avoid it.

The possible connection between this compound and a neurological disease similar to Parkinson’s, ALS and Alzheimer’s emerged from a study involving Chamorro villagers in Guam. Researchers traced the neurotoxin – BMAA (β-methylamino-L-alanine) – to the cycad seeds the Chamorros use to make flour for tortillas. BMAA is also found in blue-green algae. Animal studies have shown that monkeys fed fruit to which BMAA was added developed brain changes – neurofibrillary tangles and amyloid deposits – described as nearly identical to those found in the brain tissue of Chamorros who died from the Alzheimer’s-like disease. Notably, except for those who have chosen to live with the Chamorros, other inhabitants of Guam have not developed this disease.

(Research has also shown that BMAA can accumulate in fish and shellfish in South Florida and other areas where algae blooms occur, raising the possibility that it can enter the human food chain with potentially serious health consequences.)

We’ve known for years that some blue-green algae contain another toxin, microcystin, at levels considered unsafe. Microcystins accumulate in the liver, where they can cause irreversible damage, especially in children who have been exposed to high levels. A 2011 German study that analyzed 13 commercially distributed algae products found harmful toxins in all of them. What’s more, spirulina growing in areas with large concentrations of mercury and lead absorb these heavy metals. In addition to liver damage, contaminated spirulina can cause nausea, vomiting, weakness, rapid heartbeat, shock and death.

Spirulina is often promoted as a “superfood,” but the science addressing its nutritional benefits is scant at best. While blue-green algae is a good source of protein, you would need to consume an enormous amount to equal what you can get much more easily from nuts, legumes, whole grains and animal foods. Economically, spirulina makes no sense, since it costs about 30 times as much per gram as protein from other sources.

Some laboratory and animal studies have indicated that spirulina potentially has antiviral and anticancer effects, boosts the immune system and protects against allergic reactions, but we have no proof of any of this in humans.

Be aware that aging is still the major risk factor for Alzheimer’s disease. In some cases, BMAA may be a contributing factor.

Andrew Weil, M.D.



Paul Alan Cox et al, “Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain.” Proceedings of the Royal Society B, January 20, 2016.

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