Doctor's Note

More on the safety of blue-green algae and spirulina supplements:

For further context, check out my associated blog post: Toxin Contamination of Spirulina Supplements

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  • hermanzaum

    Not all species of cyanobacteria are poisonous. Spirulina (Arthrospira maxima e A. platensis) doesn’t seem to be dangerous to humans as I’ve been researching lately.
    However, the real risk lies when Spirulina is bought from a suspicious/shady source – the consumer may receive a toxic blue-green algae instead.

    • Michael Greger M.D.

      Thank you for your comment herman. The synthesis of some of these toxins does not appear to be species-specific. There certainly are toxic types of algae, but even what’s sold in health foods stores as blue-green algae and spirulina may idiosyncratically produce certain toxins (that’s why every batch would have to be tested, which is cost-prohibitive). Please see my other blue-green algae and spirulina videos for more background.

      • hermanzaum

        Thanks for the heads up, Dr. Greger! I’ll send the links to your videos to my dietitian/nutritionist, as she was the one that suggested that I should take both Spirulina and Chlorella. Thanks again!

      • what about organic spirulina ? toxins or not?? is every batch tested or is it safe because it is organic ?

        • sf_jeff

          What exactly does organic mean in this context? Producing billions and billions of microscopic organisms might be the one area where you actually prefer less organic.

      • Nunzio Guadagni

        I currently buy from nutrex hawaii spirulina are they reputable. They claim their products go through extreme process of making spirulina. Can you research this company. Thanks

  • LynnCS

    Oh, Oh. Out goes the spirulina/BG Algae. Thanks for the heads up. I bought it and haven’t used it so much. I am more interested in natural fruits and vegis. Who knows what we’ll find in those next. Ha!

  • psychwoman1

    Thank you for the info. I had recently read that spirulina had a protective action on cardiac muscle in chemo patients (as chemo can damage cardiac tissue). Have you ever heard that claim? Again, I appreciate the info you provide!

  • Toxins

    Hello psych!

    Check out these couple videos for more on spirulina and you will see any benefits are surely outweighed by the harms.

  • There are thousands of kinds of algae, or all colors.  I eat the wild algae. Spirulina and Chlorella are farmed.  At…  We are PROVEN to be BMAA free (is 3rd party)
    2. We are not farmed, and we are organic, removing herbicide/pesticide issues
    3. We are NSF certified, proving we are clear of all contaminants including microcystin.  I’ve been eating this 25 years.  Too bad that this mis-information is out there.  We have tons of research showing its benefits, and its safetyl.

    • Lew Payne

      Katharine – Feel free to post links to published peer-reviewed reproducible studies backing your assertion.  No need to post a ton of them – a few dozen studies, reproduced by reputable sources, should be all you need.  Even just the study names (Journal, volume and article title) should do.  Lacking this, your “tons of research” showing its benefits is but hyperbole.

  • Marychiancola

    What about Omega 3 fatty acids derived from Algae? Are those safe? My husband’s mother and grandfather both suffered from Alzheimers and I want to make sure I’m not giving him anything that may increase his risk. Thanks!

  • Rhys

    Do you know of any evidence for dietary factors in the development or progression of ALS, Lou Gehrig’s/Motor Neuron disease?

  • Perhaps you could recommend a reliable brand or store for spirulina? Try a couple of spirulina products and test its toxicity. I am interested in taking it as protein supplement and I need to be sure of my source just in case.

    • Jennifer Smith

      There is a new amazing source for truly raw living Spirulina paste. I feel this is so far superior than any powders or tablets that are processed with extreme heat. If you are looking for amazing benefits stick with food with life. Water content is life. Check them out

    • Yes there is now a company and algae research facility operated by Florida Institute of Technology Marine Lab under the usda growing Spirulina inside closed greenhouses. It is a premium raw living Spirulina in a fresh paste. The best I have ever tried by far. You can purchase direct at

  • what about organic spirulina ? hepatic toxins or not?? are organic batches tested and found to create these toxins?, or is it safer and nontoxic producing due to it being organic?

  • Billy Schoch

    I recently read that fish acquire their dha and epa omega 3’s from eating algae. If that is the case, then what is the difference between eating fish and the bats?

  • Matt Lafontaine

    I have introduced a mixture of organic Spirulina, Cod liver oil and fresh local yogurt. as well as no flush Niacin caplets to my 55% uncooked vegtable diet. I am not a vegitarian but have noticed an increase in water consumption and energy during the day. While lowering my meat intake. The effects on my body from my mixture is nothing short of amazing. More lean muscle mass with less water retention coupled with lightning fast muscle recovery time. For me, protein shakes are useless. I see absolutely no reason not to implement this in a regular diet. We all might see an Epidemic of health. I dont see my health care as a pill for every ill.

    • Deezy

      Well, I see someone watched Foodmatters…

  • Celeste

    Do you know anything about BioSuperfood? This is my main supplement but now I’m questioning it. The ingredients are listed here:

  • billyh

    You must have read my mind. A friend posted this article last night, worried about Brooks. That got me wondering about the fancy blue-green algae I use about once a month in juices and smoothies. No wonder my body doesn’t want it very often.

  • Catherine Meade

    Would fermenting spirulina inactivate potentially harmful properties?

  • Jo-Ann

    Dr. Greger, I started taking Spirulina when I read a number of research papers claiming that Spirulina heals scars. I had had major surgery and was left with a nasty scar, yet, after taking Spirulina for less then six Months the scare is 90% gone. The hardness or scare tissue is no longer there. How can something that is so bad do so much good? That is just one of some of the good I have encountered using Spirulina.

  • TuxSax

    How about growing your own spirulina at home? Wouldn’t it be safe and bacteria free if done correctly?

    • Anthony Gonsalves

      Spirulina is a bacteria. Growing your own at home won’t make a difference in “safer” spirulina because cyanobacteria simply just produce this amino acid.

  • ortal

    Hello I started to consume Spirulina and Chlorella postnatal iron deficiency and fatigue I’m breastfeeding and told me it was okay for me and the baby. Now tell me that it is full of heavy metals and toxins .. I have nothing to fear I was nursing my son? And the collection myself? I had the these symptoms: headache and muscle pain Please tell me whether I need to stop. Really makes me feel bad that I took it to improve your health and it does the opposite? I’d love a quick answer please I’m very worried about me son.

    Thank you

    • Debbie Calvello

      i have been taking Super Blue Green Algae tablets for almost 20 years and i give the powder to my pets. put it in my babies bottles with juice as well, love it, FB me for the amazing brand that i use.

  • Lana

    I use e3 live do you think this is also bad? What about wheat grass?

    • Anthony Gonsalves

      Wheatgrass isn’t a cyanobacteria, no BMAA to worry about there. As far as e3live, AFA may contain small amounts of BMAA but until we see several studies proving otherwise, we don’t quite know.

  • Worried

    Thank you. I have been taking spirulina and blue algae for several years. At first I found it gave me energy but in the last two years I have become increasing lethargic, forgetful and reduced immune system, catching colds and suffering from sinusitis. I also developed Bells palsy during this period. Could it all be related? I have just thrown my tablets in the bin.

  • Lena

    There are articles that the superfood Spirulina causes decrease in bone mineral density despite its many benefits (including for the various minerals in Spirulina which are essential for calcium absorption and strong bones).

    Hence, is spirulina safe for intake by women with surgical menopause and diagnosed with osteoporosis? Appeciate your thoughts on this.

  • JJ Zapata

    I take Klamath Blue Green Algae sold at a whole foods store. I believe it helps my anxiety although it could just be a placebo affect I am not sure. I do not want to be taking this if it could potentially be toxic :// I have been taking it since October so that’s 4 months now, I take one pill a day. If anyone has advice I would kindly appreciate it thank you. I am 22 years old!!

  • Perez

    My mother has ALS. Doctors state there is no cure. Based upon experience can I at least halt the disease from progressing? We are willing to try anything at this point.

    • Ved1

      in my opinion, the following may help: in addition to regularly taking 20g daily of 3rd party tested spirulina, avoid all carbs especially sugar and wheat products, avoid all polyunsaturated oils (sunflower, saflower, soya, sesame, etc), avoid alcohol, avoid fructose (also in fruits), take a tsp of organic coconut oil and pasture raised butter every 4 hrs, take krill oil, take astaxanthin, take cottage cheese smoothied with linseed oil and red onion and garlic, take 4 raw orgainic eggs daily smoothied with an organic tomatoe and a carrot and a paprika and spirulina, take MSM, take overcooked green tea daily (must taste bitter, eat the leaves too), eat different types of organic cheese, but avoid milk, eat lot of herbs and spices.

      • Ved1

        Also take daily Coenzyme Q10 as well as fermented
        cod liver oil

        Make sure that the astaxanthin and Coenzyme Q10 are
        not dissolved in hardened vegetable oils

        Avoid margerine and all other hardened vegetable oils

        avoid processed white salt, use himalyan salt instead

  • Redirectionalism Redirectional

    Your comments are far too vague to really say anything meaningful. Here you have the “tiny dark green leafies”, then a bigger green plant, which you do not name as bat food, and then some dead Chamorro people from BMAA. Where do the alzheimer’s patients get their BMAA from?, did they all eat tiny dark green leafies too?.

    I think you need to show a real connection here between all these, and that is something that no one can do in less then a few seconds. You even admit you are not sure when you use the word “CAN”. How am I supposed to base anything on this type of work. How about a serious study on BMAA and how it CAN get into the dark green leafies?

  • Redirectionalism Redirectional

    Where do the alzheimer’s patients get their BMAA from? I hear you can get it from Shark Meat

    You even admit you are not sure when you use the word “CAN”. How am I supposed to base anything on this type of work. How about a serious study on BMAA and how it CAN get into the dark green leafies?, I think it may only be that it is in the ROOTS of the cycad plant and dead places where there is BMAA, where nuro-toxins accumulate, and not from any specific plant so much perhaps. I would not be surprised if b-methylamino-L-alanine is in root-canals. What about cooking it?

  • Redirectionalism Redirectional

    Where do the alzheimer’s
    patients get their BMAA from? I hear you can get it from Shark Meat. You even admit you are not sure when you use
    the word “CAN”. How am I supposed to base anything on this type of
    work. How about a serious study on BMAA and how it CAN get into the dark green
    leafies?, I think it may only be that it is in the ROOTS of the cycad plant and
    dead places where there is BMAA, where nuro-toxins accumulate, and not from any
    specific plant so much perhaps. I would not be surprised if
    b-methylamino-L-alanine is in root-canals. What about cooking it?

  • Guest


  • KJ

    Wow, thank you so much for this! I had no idea. You saved me a ton of $ and possible suffering down the road. <3

  • somas

    hey fellas , I am an athlete and for the past 2 years I was suffering from gout, It was hard to continue my passion. every time I went to the field I felt the flairs on my right leg toe with accumulates full foot. Unbearable! .But for now I tried to balance by diet. I take Spirulina made in my country India. Amazingly its working . now I really feel little or no pain nor flairs on my foot. This is not scientific but practical. Just felt conveying to those who suffer the pain. I know it should be felt.
    In South India we have been using this algae for centuries to treat hepatitis , arthritis, and as an immune drink . with a strict 48 days diet to follow. basically they Prepare the Ayurvedic composition on early morning for consumption. prepared by prehistoric medical practitioner families. Living centuries in villages of south India. once you have the medication from them you have to follow certain diets strictly. think to blacklist and thing you could have for next 48 days( in tamil 1 mandalam ). This combination of the medicated algae and your diet, recycles the system and cleanses your body. even now people in south India don’t relay on liv52 for hepatitis or doesn’t seek for English medicine. they just rush to the villages and get it done. with no side effects. hence its prehistoric Tamil medication government doesn’t rule over the practitioners. If anyone need more help on this medication I could guide you.

  • Anthony Gonsalves

    I consume spirulina from Health Force and Pure Planet. While I know BMAA may be an issue…that lovely cyanobacteria is always a part of me.

  • nekomime

    I’m a vegetarian hoping to one day get pregnant. I want to take a DHA supplement when I do because I’ve heard how important it is for brain development. Currently I take omega 3 flax seed oil as a part of my routine every other day. I’ve thought about taking omega 3 algae but I’m afraid of toxins. Are algae supplements safe? How can I know if the brand I use contains any toxin contamination?

  • Anne Sanders

    Spirulina is just one of the ingredients in the ‘Vegan 5 a day +’ I take as a green powder from ‘Xenca’. I find this a wonderful product. It helps keep my body on the alkaline side and I also happened to notice that on feeling a bit off one day after eating something, I remembered I’d not taken my daily dose of Xenca. Just 10 minuted after taking it I felt 100% again. I’ve repeated this and it always works. I have a healthy diet. Take no pills apart from probiotics daily and Xenca. It’s kind of tiring and tedious (sorry) to then read that yet something ‘else’ is now not good (like spirulina) I’m always interested in information on health and food but am truly fed up of reading how one day something’s good for you, the next it isn’t and it’s happening on an almost daily basis.