GOS: A Recommended Prebiotic to Improve Your Microbiome

GOS: A Recommended Prebiotic to Improve Your Microbiome

GOS’s are a form of prebiotics that have great benefit to people with digestive issues.

What Are GOS’s?

Galacto-oligosaccharides are a chain of galactose (monosaccharide sugar) units that are produced by the enzymatic hydrolysis of lactose. Like other prebiotics, GOS’s are unabsorbed by the intestines and are fermentable in the gut by bacteria.1 Galacto-oligosaccharides seem to be the gold standard of prebiotics, and I recommend them for use in most cases of poor intestinal health.

How GOS Supplementation Reduces Endotoxin Production In The Gut

Gram-negative bacteria have a component of their cell wall known as LPS or endotoxin. Small doses of endotoxins that leak out of the intestines have been shown to consistently trigger inflammation, which is commonly known as “leaky gut.” It is normal for us to have gram-negative bacteria as flora throughout our body, but when overgrowth and virulence occur, too many can overload our bodies natural defenses to protect us and eliminate endotoxins and issues occur.2

Even worse larger doses of endotoxins that leak into the bloodstream become a serious medical condition known as endotoxemia, which causes widespread severe inflammation and organ damage/failure.3

So how do GOS’s reduce endotoxin production in the gut?

GOS’s have also been shown to be very selective and limit the growth of opportunistic bacteria including E. coli, Klebsiella, Prevotella, Salmonella typhimurium, and Clostridia in the gut.4 5

Galacto-oligosaccharides have been shown in studies to increase naturally gut flora populations of Bifidobacteria and Lactobacilli. Bifidobacteria seems to benefit greatly from GOS supplementation and increase more in number with it than any other prebiotic. Normal populations of Lactobacillus in our gut help reduce the population of opportunistic bacteria in our gut by decreasing the pH, thus reducing endotoxin load. Also, try to use a GOS supplement that was produced from Bifidobacteria enzymes for a greater synergistic effect. 6 7

Supplementation of GOS’s seems to increase SIgA levels in the intestine tract by increasing Bifidobacteria and Lactobacilli populations in the gut and reduce opportunist endotoxin producing gram-negative bacteria. Secretory IgA is a class of antibodies produced by a mucosal surface and is considered the first line of defense against endotoxins and opportunistic organisms in the gut. SIgA levels are different for everyone but when levels are too low (mucosal barrier is very damaged, the immune system not reacting to endotoxins or pathogens), or very high (immune system is overreacting to endotoxins or pathogens), leaky gut may be occurring and endotoxins leak into the bloodstream from the gut.8 9 10

GOS Supplementation Helps Improve SIBO Protocols and Recovery

Galacto-oligosaccharides have been shown in studies to cause the least amount of flatulence compared to other prebiotics. Only in levels, way above the recommended supplementation range (greater than fifteen grams) were flatulence and diarrhea reported. Even in large doses of twelve grams daily, no digestion discomfort was reported. GOS are selectively fermented and as such have a low chance of causing flatulence or SIBO. A GOS prebiotic supplement is technically considered a FODMAP, but it has lowered fermentation potential compared to other prebiotic supplements.11 12

Supplementation of GOS’s might help improve the use of Rifaximin or anti-microbial agents against SIBO. Though there is not a study done with the use of GOS and Rifaximin, there is one with the used of hydrolysed guar gum. The researchers of the study come to the conclusion that because HGG increases Bifidobacteria and Lactobacilli in the intestinal tract and restoring proper MMC transit time it helps improve SIBO outcomes. I believe that the same conclusion can be made with GOS supplementation, since GOS as a prebiotic can do both of these things and more.13 14

The process of fermenting GOS’s in the colon produces anti-microbial agents that help eliminate opportunity bacteria and limit their ability to adhere to the intestinal tract. GOS’s can also restore proper bowel function and relieve chronic constipation with its use. Finally, GOS’s improve intestinal mucosa and villi function and can help relieve leaky gut.15

Other Benefits of GOS Supplementation

There are even more reasons to supplement galacto-oligosaccharides than just improving overall gut health. GOS’s have been shown to reduce allergy severity, reduce the chance of infectious diseases, improve calcium / magnesium absorption, increase bone density, and even reduce the severity of the common cold and the flu when supplemented.16 17

My Recommended GOS Supplement

The only GOS supplement I currently recommend is Galactomune by Klaire Labs. It does contain beta glucans so use with caution if you are allergic to yeast. I recommend taking two scoops daily in place of probiotics in any of the protocols listed in Fix Your Gut.

  1. Hi John,

    It has been ~ 4 years since this entry was published; do you have any other recommendations for brands to get?
    The Klaire Labs is hard to find and expensive to get in Canada.


  2. About issues with yeast… are there food sources of GOS? Can we make GOS from a good raw milk source?

  3. I tried PHGG for a week and it gave me consistently worsening gastritis. I was hoping it would work as I have upper gut dysbiosis, oxalate, histamine, salicylate and hydrogen sulfide issues. Any reason why it would cause this?

  4. What is your opinion on resistant starch 2? What about resistant starch type 3 which seems more promising?

  5. Hi John

    thank you very much for offering your knowlegde and research to us.

    As one pathogen – Klebsiella sp. – has been mentioned above serveral times, I would be highly interested to know if in the meantime there are is more evidence if GOS is safe or not?

    I`d like to avoid anything that feeds them.
    I am on paleo/low fodmap since a long time and my microbiome is messed up. Each time I try to reintroduce complex carbs biofilm production, silent reflux, endotoxinproduction and congestion increase. The same is true for eradication treatments. Each time it gets worse.

    Thanks in advance

  6. GOS’s have also been shown to be very selective and limit the growth of opportunistic bacteria including E. coli, Klebsiella, Prevotella, Salmonella typhimurium, and Clostridia in the gut.4 5

    When I look up the references, no where does it say GOS’s work on klebsiella. Every thing I read says it is a NONO for klebsiella. Please reread the references and correct as needed.

  7. Hi John,

    Are GOS safe to use if I have an overgrowth of Morganella M. and Proteus Mirabilis? In the book you mention those two are histamine producers but no other guidance on how to control them. I’m following the UC protocol, and want to add GOS but unsure if that will stimulate them to grow?

  8. Hi John,

    Have you heard of a product called Floraphage? If so, what are your thoughts, please? Is it a worthwhile treatment if one has SIBO/yeast overgrowth?



  9. Hi John,

    Are there any more GOS products you now recommend? Galactomune is very expensive to purchase from the UK.


  10. Hi John, I’m wondering if it’s save to use GOS in combination with XOS. I’ve read in your book you don’t recommend XOS because there was not enough studies on it, has that changed recently maybe?
    The reason I’m asking is that it’s difficult to get Galactomune where I leave (Poland) and the only other product with GOS I found is Jarrow Formulas Prebiotics XOS+GOS.
    I have problems with histamine, probably because of wrong microbiom structure and don’t want to mess with that.

  11. First, thank you for all your hard work on this blog. I found the information so useful that I decided to also purchase your book as well (just received it in the mail Yesterday).

    I do have a question regarding your last statement: “I recommend taking two scoops daily in place of probiotics in any of the protocols listed in Fix Your Gut.”

    I was under the impression that the whole point of pre-biotics was to help feed the probiotics, so they could help repopulate the gut. Why would you introduce one while removing the other? Should you not take both at the same time?

    Thanks in advance for clarifying,


  12. I can’t seem to find a version of GOS that has no lactose or yeast

    • Ergomax makes one. They’re in Belgium so shipping will take longer.

  13. Hi

    I started GOS 3 days ago. I’m doing about two grams a day, one at night one in the morning.

    The first day was great, but the following to days have been miserable. I feel agitated and depressed. I thought there supposed to be no herx with gos?


    • GOS can rarely cause a herx reaction, but it is one of the least likely prebiotics to do so and for most people improves their microbiome and prevents it from occurring. It could be an immune reaction which is separate from a herx reaction.

  14. Would this still be beneficial for someone with no large intestine and only a small intestine?

  15. I asked in a group if GOS could be used in place of inulin for the nemecheck prototcol. Didn’t get many replies but wondering if you have any thoughts/ opinions regarding this question? My 5 year old has autism, apraxia of speech, and major/chronic constipation issues. Also, is GOS high glutamate? Thank for your time!

    • GOS would contain no glutamine it is a oligosaccharide not an amino acid.

    • Hi! I was wondering the same thing. My son didn’t do well with inulin. I was told to try to give him just thrive probiotics and glactoimmune by Klair labs. Have you tired this or found a good probiotic for your son? My son takes 2 prescriptions (low dose Naltrexone and Amantadine) so I always worry about something interacting with them.

  16. Hi,
    Is it ok to take up to 15 mg of activated charcoal to reduce the symptoms of die off? I am experiencing a lot of vomits and with this amount of charcoal I feel Ok but I wonder if it is too much.
    Thank you very much,

  17. Hi John Is it safe to take Galactooligosaccharides (GOS) such as Galactomune, if you have dysbiosis or sibo?


    • You will have to try it to see if you have a negative reaction to it. It may increasing bloating, but it is one of the prebiotics that are least likely to cause issues. Start with a smaller dose.

  18. I recently found this product: https://www.ergomaxsupplements.com/prebiotics-galacto-oligosaccharides

    Pure GOS according to the description.

    @John: you write to take GOS in place of probiotics. What about taking both at the same time?

  19. It gets confusing as IBS sufferers are encouraged to follow a low FODMAP diet, yet prebiotics are essential to a healthy gut. What prebiotics can someone with IBS then tolerate?

  20. I got watery diarrhea from about 1 gram of GOS. It was probably the most gentle diarrhea experience I’ve had with prebiotics; inulin, fos, potatoes starch all cause explosive type with painful gas pressure.

    I have overgrowths of prevotella and others from long term very low carb/very low fiber dieting, due to multiple food intolerances.

    I must say 2 hours after the first half gram of GOS I felt quite good and some of my symptoms lessened, quite odd, not placebo either, I am always apprehensive about prebiotics as the side effects are always quite unpleasant and long lasting for me. Despite the mild diarrhea, the relief I felt from my usually symptoms was strong enough that I feel encouraged to try again tomorrow sticking with the half gram for a while.

    So is the endotoxin fighting capability only due to the increase in bifido/lactus??

    • There might be other mechanisms that I am not aware of. Continue using it at lower doses to see if you tolerate it better. If you find any information let me know please.

    • @G. Mitata
      I’ve also been unable to tolerate the prebiotic fibers you mentioned but have had good results with Klaire GOS and larch fiber. There are a couple others I can tolerate (Acacia, konjac, pectin), but only these 2 made a dramatic, immediate, and lasting change to my stools. No more floaty, stinky stools, but softer and sinky. Maybe also try resistant starch type 3 (cooked and cooled potatoes/basmati rice) but stay away from type 2 (potato starch and green banana flour).

      I’m surprised you’d have Prevotella overgrowth from a FODMAP type diet as they digest carbs. In comparison, I also restrict certain FODMAPS, have low Prevotella, and couldn’t find an obvious bacterial overgrowths (other than some sulfate-reducers). But recently found Blastocystis infection and just finished the Australian triple therapy as herbal protocols didn’t work. I am continuing the GOS through the treatment and healing.

  21. Oligo30 claims to have GOS (Bimuno) as well as FOS, XOS, potato starch, kiwi pectin, and cocao powder. I’m curious what you think of the blend.

    With the crazy number of strains living in our gut is a wide array of prebiotics better than taking just one (similar to taking a multistrain probiotic instead of a lot of a single strain)?

    • Way too many different prebiotic’s in one supplement. Unless you have an idea of the makeup of your gut or your digestive health is decent it is like spinning a roulette will if you take it. It would be best to take one or two prebiotics and then eat a varied diet to help feed the microbiome.

  22. I’m working on repairing my gut after chemo. I take Prescript for 4 days, then Klaire factor 4 on weekends. I had a mild case of SIBO, per breath test, did the oil of oreg, barberine, monolaurdin protocol and it’s all gone (per breath test). I want to cont. to do healthy stuff for my gut. i saw your prescript article. Would taking the klaire GOS powder replace my 4 day on prescript? Then the Klaire on weekends?

    • Taking GOS would help facilitate proper gut flora and digestive health. The “probiotics” in Prescript Assist are mainly transient if they are spore formers. They mainly modulate the immmune system and do not populate the gut unless you are immunocompromised. I would run by everything with your health care professional.

  23. John..Clearly there is a need for a better GOS supplement without any additions. You should start a company! Or I will..In the future when I know how to =) Still experimenting John..Im pretty much heartburn free but I still cant eat like I used to. There is still something wrong with me. I have spent a lot of money in the process..hurts my brain. But my quality of life depends on figuring this out. My motility still sucks. I use vitamin c and magnesium to go. Without it i think id be stagnant. Im mostly grain free right now besides jasmine rice. Also no dairy besides butter and sour cream. It blows..Im taking atrantil and trying different ways to take raw garlic. Im super sensitive to it. Any of that oil on my throat and goodbye stomach contents. I just successfully ate two pressed cloves by essentially making “butter pills” haha i hallowed some cold stuff out and encased it. Still hurts though in my stomach with a meal. Im also takin glutamine and trying to be smart and eat liver and canned salmon etc for nutrition. Lots of things…I know something is wrong with me in another way too. I can no longer workout without developing trigger points in many different areas. My muscles arent working properly. I get so discouraged because I am a lot slimmer now and I cant lift and eat a lot like I love to do. I will never give up because I have no choice..I have to be healthy enough to work. I dont want to be another leech of peoples taxes..Anyhow hope youre doing well. Its my own fault I am sick. I partied a lot in the past, wish I still could, and I have a hard time with moderation…I once ate pizza for a week straight breakfast lunch and dinner. I somehow lost the pictures of all the boxes from different places. It was a metabolic experiment of sorts…stupid..and you know ive overate plenty of times to increase body temperature with ideas from a certain someone and it worked in the beginning and my digestion was beast. I was burning up and functioning properly. Now if I tried it wouldnt go anywhere and make me feel shitty..I know sibo and sifo can be caused by several factors but sometimes I think it was a food borne pathogen type of thing. Shitty meat or or too old of pizza. Ive gotten fevers for a few days out of nowhere after eating questionable things. Im sort of aware that infection and poisoning from endotoxins are two different things. Enough rambling. Im gonna make this shit my career if I figure it out.

    • Forgot to mention im trying iberogast for motility too and havent tried triphala yet. Motilpro doesnt seem like a good idea because Ive read possibly from you and others that ginger actually slows mmc function. Hmmm

    • Sorry but one more thing. I am well aware that others have ate pizza for a hell of a lot longer with much better results than I. I wasnt born with the best genetics and their expressions.. =P Im sure my job pissing me off all of the time only exacerbates everything..but I wouldnt be able to buy stuff to experiment without it. Ha! woosaa…

    • Go to a natropath. I’ve been in the same boat as you and it’s no fun. Once you get some certain diagnoses your path to health will be so, SO much easier. You need to know what you’re up against and then you will know your goal.

  24. Hey John,

    I came across a study that showed GOS, particularly the Bimuno brand, lowered morning saliva cortisol. Is this legit or just marketing?

    Also, can one take GOS everyday or do you advise against?


    • Possibly, if the GOS were to help with leaky gut, increase probiotic diversity in the microbiome, and reduce overgrowth then it would reduce immune function which in turn would reduce cortisol needed for immune upregulation. It is a broad claim but it is possible.

      I would not take it indefinitely. Maybe try some natural sources of GOS like black beans when you can tolerate them more on occasion.

      • GOS has brought me back to life. I sleep again, have energy and almost no anxiety among other benefits. It’s remarkable. I believe you suggest that if you are a non-secretor, which I am, GOS might be important to take everyday. Is this an exception to not taking it indefinitely?

        • How much do you take per day Kat and do you split the dose? thanks :D

        • I am a non secretor and have Klebsiella and. It shows possible mold toxins … from urine analysis…. good to hear you feel better I am hoping this may help with weight gain I am a very active fairly healthy gal but it has been tough the last few years to lose ten pounds. Did you notice it helped your metabolism??

  25. Oh and another question If I have issues with FOS – is GOS considered safe for me

    • Possibly, it should be safer but in some people could still cause issues.

      • I am highly sensitive to any processed FOS and a few other soluble fibers but can happily say that both GOS (Klaire Labs) and Larch powder work fantastic. Unfortunately I take both together so don’t know if one or the other is better. No bloating, flatulence, odor, or floating stools. Best supplements I’ve used yet.

  26. Is GOS good for someone if they have an overgrowth of klebsiella pneumoniae and klebsiella oxytoca?
    I would appreciate any insight on this overgrowth.
    I have done many herbals – and even did rifaximin – but I’m still having some issues with getting rid of it.

    So I came across your article above and wondered if GOS would help ?

    I know larch is suggested for kleb and I have started this recently.

    Thank you

    • Well, Klebsiella tends to not ferment GOS so it should be fine.

      It may help.

      • Not sure if this article is cited in your references, but the way I read this is that there is potential for GOS to ferment Klebsiella:


        I started using Klaire GOS a few days ago and have had an increase in symptoms…thinking in my case it is indeed being utilized by Klebsiella, sadly.

        • I have read the same thing and am hesitant to try it. How are you doing now?

    • Tonya,

      Did the GOS help you eliminate or control your Klebsiella infection?

      I have it too and am wondering if it helped you at all.


  27. Are there any GOS supplements suitable for those with a yeast allergy?

  28. hi
    any other specific supplement you can recommend?
    I cant find any GOS on iherb.com
    do you find any?

  29. Digest gold enzymes contain beta glucans. Although small amount, Would it be safe product if one has candida?

    • Possibly, beta glucans can inhibit yeast overgrowth BUT can cause issues in people with yeast and mycotoxin sensitivity.

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