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Chlorella May Help Preserve Immune Function During High Intensity Athletic Training

Sedentary women who start walking briskly on a treadmill for 45 minutes a day for a few months may cut their risk of upper respiratory tract infections in half. How exactly does exercise improve our immune system?

Approximately 95 percent of all infections are initiated at the mucosal surfaces—the moist surfaces, like our eyes, nose, and mouth. These are protected by antibodies like IgA, which provide “an immunological barrier by neutralizing and preventing viral pathogens from penetrating the body through the mucosal surfaces.” The IgA in our saliva, for example, is “the first line of defense against respiratory tract infections such as pneumonia and influenza.” As you can see in my video Preserving Athlete Immunity with Chlorella, moderate aerobic exercise—even just 30 minutes in the gym three times a week—may be all it takes to significantly boost IgA levels and significantly decrease the risk of coming down with flu-like symptoms.

We’ve known for a long time that prolonged heavy exercise, though, may reduce resistance to infectious disease, manifested by an apparent two- to six-fold increase in upper respiratory tract infection symptoms for several weeks following marathon running.

Sport coaches are advised to monitor immune function, since illness could ultimately lead to a decrease in performance. Therefore, it may be necessary to take protective actions to minimize contact with cold viruses, for example. Athletes can’t get away with just washing their hands and wearing a mask, though, because upper respiratory tract infections are often triggered by reactivations of latent viruses already inside our bodies, such as Epstein-Barr virus (EBV). As soon as our immune function dips, the virus becomes reactivated. Researchers found that IgA levels drop the day before EBV comes out of hiding and causes a spike in symptoms. “These results suggest that the appearance of [upper respiratory symptoms] is associated with reactivation of EBV and reduction of [salivary] IgA during training.”

How can we preserve immunity in athletes? In Preserving Immune Function in Athletes with Nutritional Yeast, I discussed the efficacy of using a one-celled fungi—nutritional yeast—to boost the immune systems of athletes. What about a one-celled plant?

Researchers in Japan found that IgA concentrations in breast milk could be increased by giving mothers chlorella, a unicellular, freshwater, green algae sold as powder or compressed into tablets. What about other parts of the body? Thirty tablets of chlorella a day for a month increased IgA secretion in the mouth, too. But does that actually help in a clinically meaningful way? Researchers in Canada tried to see if they could boost the efficacy of flu shots, but a chlorella-derived dietary supplement did not appear to have any effect. They were using some purified extract of chlorella, though, not the real thing.

What about giving it to athletes during training camp? High-intensity physical activity and group living create an environment ripe for infection, and, indeed, the training was so intense IgA levels significantly dropped—but not in those given chlorella each day. So, chlorella intake may attenuate the reduced IgA secretion during athletic training.

There is a caveat to the use of chlorella. See Treating Hepatitis C with Chlorella and Is Chlorella Good for You? to make up your own mind about whether the benefits outweigh the risks.

Interested in some other ways to decrease your risk of upper respiratory tract infections? See:

For the cuddliest way to protect your immune function, see my Are Cats or Dogs More Protective For Children’s Health? video.

What else can exercise do? See:

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:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

34 responses to “Chlorella May Help Preserve Immune Function During High Intensity Athletic Training

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    1. No, you have to take 30 tabs because if not, the Chlorella makers will suffer on low economy income. (sarcasm off)
      Follow always the money and you will understand if it is good for YOU or for any seller… this crap nobody needs really.
      I know a lots of sports man they run 8.000 km and more every year on the bicycle and have had no flu or upper respiratory tract infections for years – but they are not so stupid to do the exercise for any stupid challange – they do this only for there health and fun – may be this (!) is the difference. No coach tell them you are not good enough, make more effort, you are nothing etc….

    1. Wondering do other sources of beta glucan work?

      Barley and Mushrooms maybe?

      Maybe mix barley and mushroom and nutritional yeast?

      I have to re-watch the risks of chlorella.

      I don’t see the need to do the “risks” foods if there are other things I can eat.

      Are there risks to Nutritional Yeast?

        1. Thanks Ron.

          Trying to digest the nutritional yeast information.

          Baker’s get Crohn’s Disease way more often.

          It is so much higher, that they have to be more exposed to something or have pre-existing conditions, which are higher in people who want to go into making baked goods. Sweet tooth, would be a possible other guess, but I got to the Candida video and sweet tooth was a no for that.

          “They found high amounts of E. coli and Serratia marcescens and Candida tropicalis in the patients with Crohn’s ― significantly more so than in the family members without Crohn’s, as well as the individuals from families without a history of Crohn’s disease.

          The researchers ran additional tests to see what happened when the two bacteria and the fungus interacted. Together the organisms produced a thin, slimy layer of microorganisms they say would be able to adhere to various organs in the body, including the intestines, which would likely cause the same type of inflammation known to affect people with Crohn’s.”

          Okay, except my mind backs back up to the Bakers. If they are the ones getting it the most, that means they have to have something, which causes the conditions in the first place.

          It is bakers, not brewery workers?

          Just me, thinking aloud.

          I need someone with more understanding to tell me that the Nutritional Yeast at too high a level, for too long, isn’t what caused it in the first place.

          Dr. Greger didn’t point in that direction, but those of us who have started using Nutritional Yeast and who might start using it in cheese eventually would like to know that it isn’t gonna be a situation where 10 years from now they will be saying “bakers” and “vegans” and somehow not beer drinkers (does the alcohol prevent the whole bacterial and fungal thing or something.)

          Yes, it is so far over my head that I am grasping for understanding.

          Anybody else have any concepts?

            1. My mind just went into a mental loop.

              The question should be:

              Do bakers who are vegan get Crohn’s at a lower rate than bakers who are meat eaters? (And does that change if they live with a meat eater and have a dog?)

              Do vegans who happen to be bakers have it at higher levels than other vegans?

              Do vegans who use Nutritional Yeast a lot have it at higher levels than other vegans?
              (And I have to cross beer drinking vegans off the study list, because I can’t mentally handle too many variables.)

              1. I am not trusting the microbiome answer until people say why bakers would have more of it based on an ingredient or environmental toxin bringing more ecoli, etc.

                I say it, because bakers have more than all the other SAD groups and the SAD groups eat plenty of baked goods as far as I can see.

                  1. Pondering the flour. Fiber removed. Some gut microbiome bacteria can’t use fiber as well as other bacteria.


                    Pondering that, because in smokers it is an increase in Bacteroides-Prevotella.

                    Guessing that it isn’t that more bakers smoke.

                    “Smoking and lack of exercise can significantly impact the large bowel (and potentially the microbiota) as they are risk factors for CRC [37]. Indeed, smoking has a significant influence on gut microbiota composition, increasing Bacteroides-Prevotella in individuals with Crohn’s Disease (CD) and healthy individuals [38]. Smoking-induced changes in microbial populations could potentially contribute to increased risk of CD. Air-borne toxic particles can reach the large bowel via mucociliary clearance from the lungs, and increased environmental pollution associated with industrialization could contribute to concomitant increases in IBD cases [39].”

                    Okay, I ended up Googling Butyrate and Crohn’s, since it was a “good guy bacteria” word I remembered and think I circled back around to things Dr. Greger has already covered.


                    So maybe the whole bakers eat lots of flour, which doesn’t have fiber theory might be why either WFPB and Keto could help with it.

                    And Keto people will point to the white flour and act like it is what WFPB people eat and WFPB people also divorce themselves from it as a carbohydrate, the same way Keto divorces itself from transfats as a fat in their studies.

                    I am not sure I am right about any of it, but the fact that so many sources just say that they don’t really know what causes it, lack of fiber messing with the gut bacteria is at least something I can look up.

                    1. I guess I would need to know if when the Plant Based diet was used, if they also removed sugar or white flour or just animal products.

                      If they didn’t remove the white flour or sugar, things would get interesting.

                    2. They could do a Gerson style versus Fiber and see whether it was the antioxidants or gut bacteria or if the food needed the fiber to help.


                      Would that accomplish something, or just in my understanding?

                    3. I feel like the Bakers getting it and Plant Based healing it and Keto also improving it….

                      It just seems like they could figure it out in one well-designed study.

                      Vegan bakers versus non-vegan bakers
                      Whole grain bakers versus White flour bakers and whether they snack on their products.

                      Vegans who get it, if they do, versus WFPB who get it, if they do and adding in the nutritional yeast versus no nutritional yeast.

                      And Keto who go into remission, if they really do.

                      Yes, it is probably 5 studies.

                    4. But it getting better with Keto and Keto not having fiber brings me back to:

                      Is Bakers yeast or something in flour, or sugar causal of the gut microbiome thing?

                      It would be dose dependent or all of America would have it.

                      If Bakers yeast changes PH or has something to increase e.coli….. Maybe causal?

                      Then I would have to not mega dose Nutritional Yeast.

                      Back to the beer drinkers and are all those yeasts the same microbiome wise?

                      Okay my mind is breaking down again. Sleep.

                    5. The problem is that Americans eat so much white flour, sugar and don’t eat fiber either.

                      What distinguishes bakers? Is it that their tasting the products ends up being more than the junk food the SAD eats?

                      Or is there some strange factor like food coloring or fondant?

                    6. Bakers breathe flour dust every day for hours un-like any other job. I don’t believe it’s what they eat as much as what they breathe every shift, whether they are vegan or not.

                1. As an amateur baker, I can tell you that the thing you may be missing about bakers is that they inhale flour constantly (not intentionally of course!). Given that wheat is basically a grass and grasses cause immune responses in a lot of people, it’s possible that prolonged inhalation of wheat (over years) could trigger an auto-immune condition.

                  That’s just my hypothesis, and not one that I can recall reading about. I don’t know if it’s been studied.

              1. Okay, Round Up just came to mind, because organic has a different microbiome and I am pondering “dose” and Bakers Yeast, Brewers Yeast, Nutritional Yeast.

                It makes me not want to do vegan cheese as often.

                I know that there are no studies even saying bakers yeast causes anything, but most of America eats baked goods regularly, but bakers do something differently to be this high subset.

                Leaky gut

                But if they have leaky gut more than it should be easy to narrow, because smokers also do.

                I can’t remember the odd things which increased lung cancer..

                So much to think about, but it is going to get me to buy another bottle of B13.

                I have been in the Nutritoonal Yeast source category this month.

                Hoping I can figure out a difference between Bakers Yeast and Nutritional Yeast and I am hoping the study with the Plant Based diet didn’t take away the Bakers yeast so I can do a mathematical process of vegetable microbiome is stronger and neutralizes the baking bad guys.

                1. So with the smokers, it is gut microbiome bacteria and fungus, too?

                  Not holes in the stomach or something?

                  Wondering if they have examined the bacteria on tobacco products?

                  They are saying that they haven’t linked it to diet yet.

                  Seems like they have the microbiome data and the who gets it data and they can measure the gut microbiome of those in remission and they have the bacteria of a lot of foods.

                  They just need to pull it together.

                  1. They have studied: alcohol and smoking and gut microbiome


                    Maybe bakers have a lot of time during cooking and they take a smoking or drinking break?

                    Doubt it. I read articles, which said that they don’t associate it with any particular diet, but it seems like a particular diet SHOULD be the answer should the answer for the bakers.

                    I know I don’t have the ability to prove it yet, but I don’t like the answer saying that bakers already have Crohns and the yeast makes the symptoms worse.

                    I don’t know who to argue with about it, so I am just going to put:

                    Nutritional Yeast? and give myself the advice to not over-use it.

              2. As scientists have said, gut bacteria does prompt you directly through your nervous system for the food the bacteria thrives on.

      1. Deb,
        The problem is if you throw barley and mushrooms into a soup, say, add nutritional yeast and some vegetables, it might improve your health, but it may be delicious, and then people won’t give us credit for being virtuous. The other problems is you may want to eat this healthy food frequently, so watch out! :)
        John S

  1. This subject didn’t generate a Kreb’s Cycle in your comments.. Maybe glycolysis.

    Sorry moderators that I am genuinely trying to learn these things for the first time.

  2. Hi
    Just got this in my feed from Blinkist (book summaries)>
    The Plant Paradox
    The Hidden Dangers in “Healthy” Foods That Cause Disease and Weight Gain
    By Steven R. Gundry (Cardiologist)
    Maybe you would like to take a look at it and give your readers/viewers your view.

    1. This has been reviewed as bad advice here and elsewhere by other food scientists. Grundy has a conflict of interest in that he sells stuff to save you from “the bad” lectins. Nearly every plant has lectins. They are so high in red beans, some people had died by cooking them wrong. All canned beans are cooked safely except for the high salt variety.

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