Should We Take Chlorella to Boost Natural Killer Cell Activity?

Treating Hepatitis C with Chlorella

Multiple studies published over the last few decades suggest that exercise can mitigate the decline in immune function as we age. Exercising can boost the activity of natural killer cells, our immune soldiers that focus on eliminating both tumor cells and virus-infected cells.

In my video, Treating Hepatits C with Chlorella, you can see the clear difference in natural killer cell activity between women involved in athletic competitions and their sedentary counterparts. There is a growing consensus that natural killers appear to be the immune system component that is most responsive to the exercise across the board, in populations ranging from older women to younger men. Even just moderate exercise, such as daily walking, appears to significantly improve natural killer cell activity within six weeks. This may be why exercise helps protect against cancer.

On the other hand, sustained, vigorous exercise may actually impair natural killer cell immunity, which may be one reason endurance athletes like marathon runners appear more likely to get upper respiratory tract infections. But could there be a natural solution?

Petri dish and animal studies have suggested that the green algae chlorella can affect natural killer cell activity. However, there was no direct evidence for the effect of chlorella supplementation in humans, until a South Korean randomized double-blind placebo controlled trial gave subjects about two teaspoons of chlorella a day for eight weeks. Compared to placebo, those getting chlorella had a significant increase in natural killer cell activity.

Do these results actually translate into clinical benefits? It is estimated that up to four million people in the U.S. have chronic hepatitis C virus infection, the leading cause of liver transplants, estimated to kill a quarter million Americans this decade. The current treatment is costly and brutal, costing up to $85,000, and nearly half can’t even complete the treatment, due in part to the many complications associated with the treatment. That’s why there’s such a need for novel treatment options.

A study out of the World Journal of Gastroenterology put chlorella to the test for chronic hepatitis C. After three months of chlorella, subjects reported improvements in quality of life, but that could have just been a placebo effect since the control group wasn’t given green sugar pills. However, a significant improvement in ALT is harder to explain. ALT is a marker of liver inflammation, and improvements in ALT could be explained by a beneficial immunostimulatory effect of chlorella supplementation.

No serious adverse effects were reported in the study; so, why not give chlorella a try? Well, the brand the researchers used, Sun Chlorella, was tied to a disturbing case report. A 48-year old woman in Omaha suffered a psychotic break, out of the blue, two months after starting chlorella. Physicians stopped it and started her on an antipsychotic drug, and a week later she was fine. Chlorella has never been linked to psychosis before; so, presumably it was just a coincidence that the psychosis started after she started taking chlorella, and the reason she felt better after stopping it was because the drug was kicking in. But seven weeks later, still on the drug, she became psychotic again after starting back on the chlorella. They stopped the chlorella again—this time that’s all they did—and the psychosis resolved.

Maybe it wasn’t the chlorella itself, but some toxic impurity or adulteration? We don’t know. While chlorella is marketed to promote mental health, this case underscores the importance of educating the public about the potential adverse effects and the need for more research in herbal products being marketed in the United States.

That psychosis case report makes me nervous. Unlike blue-green algae, which can produce neurotoxins (Is Blue-Green Algae Good for You?), chlorella does not (Is Chlorella Good for you?), but neither does spirulina; yet, toxins have been found in spirulina supplements, presumably due to contaminants (Another Update on Spirulina).

There are other ways to counter the impact of over-strenuous exercise. See:

And other ways of Boosting Natural Killer Cell Activity.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, From Table to Able, and Food as Medicine.

Image Credit: Roland Tanglao / Flickr

  • Lisa

    does Dr. Gregor and team have any research on whether phytoplankton is safe to take? I currently take Ocean’s brand.

    • Thea

      Lisa: I found one ‘Ask the Doctor’ which mentions phytoplankton, but probably doesn’t fully answer your question.

      I’m curious, why are you taking it? What is the hoped-for benefit?

      • Lisa

        I am led to believe through research that it is the single food in which all life evolved. The lowest food on the food chain that feeds all ocean life and thus all land life as well. There the intended effect is to bypass having to eat the fish to get it into my cells.

        • Thea

          Lisa: Thank you for your reply. That logic does not make sense to me, but I also would guess that it would not hurt to eat them as long as they are not contaminated. Thank you for sharing your thoughts. Good luck.

        • Tom Goff

          Some plankton are actually animals so, as a vegetarian, I avoid eating them.

          • Lisa

            See above link I gave Thea, Tom.

          • Tom Goff

            Thanks Lisa. I’d always previously seen them referred to as (marine) algae which is probably why I became confused.

          • Lisa

            What is marine phytoplankton – Much like chlorella and spirulina, marine phytoplankton is a single-celled organism that’s been on planet Earth for literally billions of years. It is the life form responsible for creating an oxygen-rich environment on our planet. Without it, the atmosphere would have remains inhospitable to humans and other mammals that depend on oxygen, so it is no exaggeration to say that marine phytoplankton created the opportunity for human life on Earth.
            So that’s why I was asking. I am currently taking it and wondered if Dr. Greggor had researched it and whether it is safe.

          • Tom Goff

            Thanks Lisa. Is that the Oceans Alive brand you use? I suspect Dr Greger hasn’t researched it unless there is an analysis in the published scientific literature.

  • guest

    Are there any risks of boosting NK cells too much? Can one end up developing irreversible autoimmune diseases? Thanks

  • Anfort Schnittli

    Are omega-3s from landfarms safe (dha and epa)? I take the testa brand. Sure, a controlled environment does rule out many sources of contamination – but if something goes wrong there, only intensive screening would find possible contaminations ….

    • TR M

      Go to the consumer reports section. If it isn’t listed then you are taking your chances. Given the amount of pollution in the rain and rivers even land based will not be clean (IMHO).

      • Anfort Schnittli

        Thanks for that one. I was under the impression that these algae are produced in close environment, eg. controlled water supply, tap water of course can be polluted, too. My main concern was that the algae themselves could produce unfavourable chemicals.

  • Mikee

    This article is very confusing. I saw Dr Greger reposting this article about chlorella from time to time. On one hand, Dr Greger said that Chlorella can Boost Natural Killer Cell Activity. On the other hand, Dr Greger cited the case of a 48 year old lady suffering psychotic break after taking Chlorella. Is it an isolated case where the Chlorella is contaminated or is Chlorella not safe? Dr Greger can help us by doing more studies to state definitively that it’s safe or not safe.

    • Thea

      Mikee: Dr. Greger is giving us all the information available. From the post above: “We don’t know. … need for more research ….”

      You wrote: ” Dr Greger can help us by doing more studies …” I’m guessing Dr. Greger would love to be able to do studies, but he is not in the ‘study business’. Dr. Greger doesn’t do any studies. Instead, Dr. Greger reviews the literature (the studies that the many, many scientists out there have done) to let us know what the body of evidence says about various topics. Sometimes (many times?) the information available simply isn’t definitive. It is important for Dr. Greger to let us know the pros and cons of various foods and not just give one side. This is what he has done.

      What to do when the information is so murky? You have to weigh the risks and benefits against your own values to decide how to proceed. For example, how risk adverse are you? If you are very risk adverse, you may not want to take a chance that the chlorella you buy may be contaminated. And maybe your diet is excellent and you never get sick so you don’t need that extra immune boost from chlorella. On the other hand, maybe your diet isn’t so good and you have been getting sick a lot lately. And maybe that one case study doesn’t scare you. So, in that case, taking chlorella may be a good idea for you.

      Make sense?

      I *totally* agree with you that we need lots more nutrition studies. I would love to see our research money going to work in ways that would actually be helpful. We need a way to change the way research decisions are made. That is a project way beyond the scope of this site. But hopefully someone, somewhere will take up the fight…

      • SeedyCharacter

        Thea, I just want to take this moment to thank you for your incredible communication/writing skills and for your breadth of knowledge about nutrition and the site. You have responded to countless queries/comments, consistently providing exceptional clarity and resources–and always with a positive spirit. The community is very lucky to have you!

        • Thea

          SeedyCharacter: Wow. That’s such nice feedback!! Thank you so much for your encouragement. I have grown to respect your posts. It is nice to be mutually appreciated. :-)

          • SeedyCharacter

            Aw, shucks, thank YOU for your kudos about my posts. A mutual appreciation society we have established here. :-)

        • JS Baker

          I agree with SeedyCharacter. Thea, you are amazingly caring and respectful in all of your replies. Through your consistent example (and your occasional admonition to others) you help create this healthy environment for dialogue and learning.

          • Thea

            JS Baker: That is super high praise. Thank you so much for the feedback. Given the vitriol on other forums, I’m very proud of the NutritionFacts community. If I have had a role in the form this forum has taken, that makes all the hours of volunteering worth it.

      • jj

        ” On the other hand, maybe your diet isn’t so good and you have been getting sick a lot lately. And maybe that one case study doesn’t scare you. So, in that case, taking chlorella may be a good idea for you.”

        Why not clean up the diet before resorting to chlorella?

        • Thea

          That’s certainly an option! But everyone’s situation is different. I wouldn’t presume to say that it never makes sense for someone to take chlorella.

      • Mikee (still confused)

        Thea, please don’t be mistaken that my comment is in anyway “critical” of Dr Greger. I do look up to his review of studies and his ability to condense complex research into something that an average working person can “digest” in a few minutes of time everyday. Like I said, I do lookup to Dr Greger advise but at the same time, I understand that not all good foods that he recommended should be eaten by everyone because we are all different. For instance turmeric brings benefits to people but some people may be allergic to it and develop rashes. But Dr Greger statement that turmeric is beneficial for people based on the studies will be sufficient for me to consume turmeric. But if I develop some allergies (which I don’t – just an example) then I still think that turmeric is beneficial for ‘most’ people, just not me. But a statement that turmeric is good except for some people who may develop rashes. will confuse “common” people like me :)

        P.S. I love watching Dr Greger video and that’s is something I look forward to do every morning. Dr Greger has a sense of humor while presenting complex health concept.

        • Thea

          Mikee: It would have been fine if you were being critical. I like people who are truly, thoughtfully critical thinkers. Take care.

    • Lisa

      The lady taking the drug for pyschosis is a billion times more harmful than chlorella. I am quite sure that it was the drug and not the supplement that led to her second break, as is consistent with most drugs.

      • Psych MD

        These are absurd conclusions.

        • Lisa

          Psychotropic Drugs cause brain damage to cells.

          • Psych MD

            Psychosis causes brain damage. Just as a heart attack destroys cardiac tissue a “brain attack” destroys brain tissue. There are numerous psychotropic drugs that actually preserve brain tissue by increasing brain-derived neurotrophic factor and decreasing inflamation. To make a blanket statement that psychotopic drugs cause brain damage is like saying food makes you fat.

          • Lisa

            Unfortunately, I know first hand. I will attest to severe damage of even the smallest doses of those drugs. They are poison. If you don’t believe me, try taking it for a week and see what happens. If you won’t do it, then I think you know that I am right. I can see by your signature that you are a doc who hands this out so therefore I will not change your mind as big pharma has taught you only what they want you to know. They cause brain and nervous system damage. Period.

  • TR M

    Tart cherry (and/or extract) can help workout recovery times as well.

  • Jenny

    Does anyone have any thoughts on whether someone with an autoimmune disease (autoimmune hepatitis) is best avoiding something that stimulates natural killer cell activity? I remember the mushroom video commented on studies showing mushrooms were okay for people with autoimmune disease, in that case where a different mechanism was at work. (I can confirm mushrooms are fine in my case, my liver function tests are not affected by mushrooms.) I have noticed that my liver function tests are slightly higher when I have exercised, but I do not understand why. Thanks for any comments. I appreciate that this is more about AIH than chlorella, but I have found very little nutritional info relevant to this condition and thought someone here could comment. Many thanks.

    • guest

      I would avoid chlorella if I were you. Interestingly, John Hopkins Lupus center, maybe #1 in the world, says to avoid things like garlic, echinacea, and some of things, as they are known to stimulate the immune system. Lupus is an autoimmune disease. I’d eat a bland diet, no spices or herbs. Keep it simple.

      • Wilma Laura Wiggins

        So you believe people with lupus should have poor immune systems?

    • Jenny

      Thank you for your comments. Any more will be received with interest and appreciation. I think this is a fascinating and difficult topic, with much research to be done.

  • Nanaverm

    I know this article was about chlorella, but an important nutrient for liver function is silymarin, or milk thistle extract.

  • Matt K

    Hepatits? I don’t want to know what that is…

  • kassikat

    Wow, I take chlorella every day because it is a great supplement for vegans, I didn’t realize it was helping my immune system too! I have a question that is off topic. Do you know of any studies about the acids in honey that render it unusable for humans? I read an article by T C Fry and just wanted clarification. Thanks!!

  • susan

    Chlorella can pull heavy metals like mercury out of the organs, but it is generally not strong enough to bind all of the available mercury, and especially that which has crossed the blood brain barrier. It would make sense to me that circulating mercury could lead to psychosis. I have had a less dramatic experience while taking chlorella…after a few weeks, finding myself feeling very depressed and tearful, which is not my usual state. I am pretty certain that the chlorella was pulling mercury out of my tissues but was not strong enough to bind to all of it and carry it out of the body, leaving it circling in my bloodstream.
    Susan Abramson, MHS, HHC, RYT

    • Anthony

      Yes. My ex-girlfriend claims 2 years of chlorella consumption saved her life as she was in a hospital bed dying from mercury poisoning. I’m not sure why, maybe she had all her amalgum fillings out at once.

  • easyout

    I can’t believe that because of just one case of a psychotic episode that chlorella was deemed a possible problem. Why even take the time to list one case. One case means nothing. When a person starts detoxing from heavy metals, of which Chlorella is specifically noted for, which again I’m surprised this wasn’t mentioned, many cases of very specific mental episodes have transpired. Detoxing can cause multiple side effects as the body is purging toxins. This also wasn’t mentioned. The only negative I’ve seen on Chlorella, are studies showing it depletes copper from the body. So one has to ask, should one be broad minded enough to speak of Chlorella and all it’s positive and negative virtues, and not just one very narrow view.

  • jostoich

    The problem with chlorella for me was the iron content. Chlorella contains iron and will raise iron levels. Iron is potentially toxic because the human body has a limited capacity to excrete iron. Iron can build up in the body. Also, iron has been shown to increase viral replication for some conditions. I’m surprised to see it was indicated for HCv as a common problem among those with Hep C is iron overload or hemochromatosis. I had HCv for more than 30 yrs. and that was the case for me. Thus, I had to avoid iron rich foods and supplements such as spirulina and chlorella. I was treated with the new drug combo last year (Harvoni) for 12 wks. It is not like the former treatments of Interferon and Ribavarin. The side effects are mild and chances of an adverse event are very rare. I attained sustained virological response (SVR) and have been undetectable for 8 months post treatment.

    • Thea

      jostoich: I can’t comment on your particular situation, but you may be interested to know that the body is generally pretty good at regulating plant based iron (to filter input, not to expell). It is animal based iron that people generally have to watch out for. Dr. Greger covers this topic in these videos:
      Why don’t you take a look and see if they are helpful? I’m glad the new treatment is working for you.

      • Anthony

        Yeah I have read that in several books, plant sources of iron are better absorbed and used in the body than animal sources (non-heme v heme).

  • James

    I take two grams daily in this organic tableted form and have never been healthier. Greenest food on earth!

  • James Quinn

    I consider it a must for detox and overall immune support. Thanks for the article