Leaky Gut: Fact or Fad?

by Alejandra "Alex" Ruani — Get free science updates here.

Leaky Gut Syndrome is often the subject of blogs and forums, along with ways to “heal” your gut.

But have you ever thought about what ‘Leaky Gut’ actually is?  What causes it? And what are the consequences of having a ‘Leaky Gut’?

More importantly, is there any science behind it – or is it just a fad?

This report will answer all of these questions.

Grab “Leaky Gut: Fact or Fad?” below:


Download PDF NOW!


Conveniently download this 40-page science report. Contains links to extra reading materials and scientific references.

Topics covered in this report:

  1. Leaking some questions in
  2. Let’s cover the basics first
  3. Absorption ‘through’ cells
  4. Absorption ‘inbetween’ cells
  5. Transcellular vs. paracellular path
  6. Gut lining as a protective barrier
  7. So, what is ‘Leaky Gut’?
  8. Tight junction barrier dysfunction
  9. Is ‘Leaky Gut’ medically recognised?
  10. ‘Leaky Gut Syndrome’ diagnosis
  11. Is ‘Leaky Gut’ a condition?
  12. Causes of damage to the gut lining
  13. Gluten and coeliac disease
  14. Zonulin and gut permeability
  15. Gluten sensitivity
  16. FODMAPs in grains
  17. Industrial food additives
  18. Nutrient deficiencies
  19. Medications
  20. Alcoholic drinks
  21. Chronic stress
  22. Sleep deprivation
  23. Chronic diseases
  24. Health effects of a permeable gut
  25. Prevention and treatment
  26. More research is needed
  27. ‘Leaky Gut Syndrome’: fact or fad?
  28. Your key takeaways
  29. Learn more
  30. References and resources


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And I'd love to hear from you in the comments below:

  1. What's your number one discovery from this report?
  2. What does it mean to you and those you help?
  3. Are there any action steps you would take, or things you would change as a result of this report?

Share your own insights with me and your fellow readers!

Alex Ruani leads the research division at The Health Sciences Academy, where she and her team make sense of complex scientific literature and translate it into easy-to-understand practical concepts for students. She is a Harvard-trained scientific researcher who specialises in cravings and appetite neurobiology, nutrition biochemistry, and nutrigenomics. Besides investigating and teaching the latest advances in health and nutrition science, Alex makes it easier to be smarter with her free Science Catch-ups every other Thursday.
Connect with Alex via email.

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  • Marion Foreman

    Reply Reply March 5, 2015

    thanks for another great article – its really good to get these every week. I have many clients who struggle to lose that elusive last 3 kgs. Can you recommend one of your courses to help me to help them? We go through all the basics of stress, sleep, hydration, exercise, food but still those extra few pounds cling on! thanks, marion

    • Alex

      Reply Reply March 5, 2015

      Hi Marion – love to hear you’re enjoying them! Have you looked at Advanced Sports and Exercise Nutrition? Particularly relevant to PT clients and athletes, certain small tweaks can result in further body composition adaptations :-)

    • Gianpiero

      Reply Reply March 5, 2015

      I believe that this is one of the main important subjects of our health in years to come. We are therefore responsible of making this one of our main focuses in human health, and expected to invest a lot of research into bettering this field of understanding. We as humans depend on our bodies to take care of themselves when we let food pass our mouth, and strengthening our tool for getting the nutrients to us through food, is the most important health advantage we can all benefit from!!

  • Val

    Reply Reply March 5, 2015

    Very interesting. Nearly everyone I know (including myself) seems to have some problem with their digestive system. Personally, I blame the modern pre-prepared food that we’ve all been accustomed to buying and eating. If we can go back to eating just fresh food without the numerous additives, our guts would be in a better state.
    We are constantly told to cut down (or cut out) alcohol, get more sleep, more exercise etc. I know this is the way to go but to do this and stick to it can be so difficult in today’s modern world.

  • Elizabeth Lawrence

    Reply Reply March 5, 2015

    Thank you so much for the article. I am a coeliac which has had a devastating affect on my life as it has resulted in other “autoimmune” issues. Reading this article (and previouse weeks) made total sense. Many of the facts that were mentioned resonated with me on a personal level as well as with clients that I see. When trying to discover what is causing weight gain or weight loss I encourage my clients to keep a very detailed food diary, which can tell me so much in both what they are eating as well as their mind set. In many cases there is often a link between the sugars/glucose that a client consumes that has an impact on their health. When reducing and even eliminating the amount of processed foods they eat, clients notice a change in their bowel movement as well as it having amazing positive health benefits.
    A well written piece and something I will certainly be passing on to clients and colleagues. I love receiving my Thursday articles and save them for future reference. Thank you.

    • Alex

      Reply Reply March 5, 2015

      Elizabeth – thanks so much for your insightful comment, love to hear you’re helping others with this! CD is a complex genetic disorder and although you may have the gene variations that predispose you to it, when you remove the trigger (gluten) the phenotype (autoimmunity) tends to go away. Regarding mindset, we’ll soon touch on the microbiome-brain-behaviour connection, the discoveries on this are fascinating :)

  • Pamela Stocks

    Reply Reply March 5, 2015

    As someone diagnosed with Myalgic encephalomyelitis (ME), fibromyalgia and IBS, amongst other things, I have come across the term “Leaky Gut” on many occasions, but, being sceptical, not known what to make of it. For me, this has to be your most useful report to date and has helped me no end in trying to make sense of the issue and in understanding why certain things affect me either positively or negatively. Thank you so much Alex.

    • Alex

      Reply Reply March 5, 2015

      Pamela – you’re so welcome, glad you found it useful! And thanks for sharing, I’m sorry to hear about your diagnosis, we’ll definitely be talking more about this in future reports. Take good care of yourself :-)

  • Sam Metson

    Reply Reply March 5, 2015

    Pre-biblical wheats Einkorn and Emmer only had 14 and 28 chromosomes respectively, whereas the modern semi-dwarf varieties that we farmers grow today has 42 chromosomes. The most recent dramatic changes in wheat breeding occurred in the late 1950’s where radiation and chemicals were used to splice parts on wheat plants to improve yields by shortening the straw to below half its natural length and increase the number of grain sites on the ear. This is when so many extra chromosomes were introduced bringing with them all the extra chemistry that causes us so many allergic and food sensitivity problems. According the Dr William Bailey of “Wheat Belly” fame this is when zonulin appeared and started to undermine our gut health. Hyper-permeability of the intestinal lining in the form of widened tight junctures also causes the villi and micro-villi to flatten in a compact layer – it may look as if the villi have vanished. This further stops the absorption of many nutrients even though they may be in a well balanced diet. This creates imbalances in function and deviation from a state of homeostasis, apart from the over loading of the liver and kidneys in dealing with excessive “junk” in the bloodstream, that in turn sets off a massive auto-immune response. The pharmaceutical companies must love this situation, as their focus is on drugs to treat symptoms, and not attempt to remove underlying causal factors. Leaky gut must be the starting point of most chronic ailments that we now suffer now in the western world. An intact intestinal barrier is a pre-requisite for good health. It is such a major component of our defence battle against the outside world despite the fact it is buried deep within us.

  • Darshi Shah

    Reply Reply March 5, 2015

    Hi Alex, Thanks for a well written summary over so much research. i have personal experience here (NCGS), so I also dived into some research articles referenced.

    I think I incorrectly interpreted something from your report, and I wanted to:

    1. Make sure I understood it correctly
    2. Ensure you were not implying something else unfairly

    On page 18, Zonulin & gut permeability: you have a point that states “…zonulin causing gut permeability has only been seen in individuals who are genetically predisposed to an abnormal activation of the zonulin pathway, …”
    This led me to believe that only those with genetic tendency for CD, T1D, IBD, etc are impacted by zonulin-gut permeability.
    But, the research by Fasano goes on to describe people with asthma, allergies, etc. So i don’t think this is entirely accurate. Also the study (or the main study – i should clarify) that takes a sampling of CD diagnosed people only CANNOT imply that only people with CD are impacted by zonulin. right? What we don’t know (because there have been no studies yet), we cannot hypothesize about or imply unfairly. right?

    Again – I loved the report, and really see the amount of time and energy you put into the summarizations. Especially after going through the research, i see you did a great job overall. I just want to ensure I am understanding this correctly. If I am wrong, I absolutely want to know; and want to understand it correctly.

    • Alex

      Reply Reply March 5, 2015

      Hi Darshi – glad you enjoyed the report, thanks so much for your feedback :-)

      As for your question, the abnormal activation of the zonulin pathway by gluten is observed only in those with a gene alteration (a modifier allele) on Chromosome 16.

      In other words, if you don’t have this gene mutation, gluten won’t cause your body to make more zonulin.

      So our next question is: could I have this gene alteration? Thanks to new exome sequencing technology, you may be able to find out!

      But to date, there’s no data showing this pathogenic mutation in individuals without an immune-related disorder. I don’t think anyone is saying that the zonulin gene alteration is exclusive to those with immune disorders, if that’s what you’re getting at, but so far we know it’s only been reported in those with certain immune conditions along with other detected gene mutations (mixed, and not in isolation). Lists are exemplificative and not exhaustive.

      As we highlight in the report (quite a few times), more peer-reviewed research is needed before making absolute statements.

      I hope this helps answer your question? :-)

      • Kate J.

        Reply Reply March 28, 2015

        I just saw a piece with Alessio Fasano the scientist that discovered zonulin and he explained the same thing in your response to Darshi. He also said he doesnt like using the words leaky gut because the term is misleading and people confuse it with a condition and it is not. I think he is annoyed that the so called experts misquote his studies to be honest.
        You and your team and the health sciences academy are brilliant and I learn a lot from everything you teach!!

  • Anne

    Reply Reply March 5, 2015

    I have learnt loads of new things in this report
    … it’s a science fest!!!

    You are amazing Alex

    I used to be a paleo fan but have been dissapointed by the lack of transparency in what paleo bloggers and forums say.

    They tend to cherry pick parts of a study that support their argument and discard others thay destroy it.

    For example, Robb Wolf uses the Fasano zonulin studies but doesnt explain what you say here. They dont go into the detail of genetics but hint that everyone has a problem with zonulin…. I even believed it myself until you explained this

    I would respect them more if they told me that science doesnt have all the answers instead of making exaggerated claims and plastering random study citations all over the place without explaining the logic.

    My biggest disappointment with Paleo advocates is that they refuse to accept red meat-cancer associations but conveniently embrace other associations like gut permeability-health disorders. So eating red meat which is associated with a deadly disease is okay but eating gluten isnt?? They dont make sense. Why dont they admit that they dont know everything there is to know??

    I mean they dont stop eating red meat despite the associations but stop eating gluten because of the associations??

    I follow a healthy diet of whole foods and hardly any processed stuff. I even eat red meat. I also reintroduced gluten slowly and have no issues with it. Going paleo was my excuse because i was eating way too many cakes and biscuits!

    I then went onto following other blogs that claim to be evidence based but then they use the words leaky gut everywhere? Oh boy…

    I think your work is one of the best online and wished everyone could access it..
    I am fed up with bad science and sensationalistic statements.

    I am addicted to your reports…!!!! cant wait to see what you have in store for next Thur!

  • Rony

    Reply Reply March 5, 2015

    What a report, one of my favourite Alex. I must say I agree with Anne. Some paleo bloggers are okay with having wine and margaritas which make the gut more permeable but ban gluten.?. I myself enjoy the paleo lifestyle but the arguments paleo blogs use to justify it are contradictory. Thanks for this eye-opener and for explaining everything clearly. One can see the effort that goes into your work.

  • Lillian

    Reply Reply March 5, 2015


    My number one discovery is the synthetic additives. I will pay more attention to that.
    I have a stressful job and not more than 6 hs sleep so I think doing something about that is a priority. I also learnt more from your comments Alex, interesting exchange with Elizabeth and Darshi. Thanks for all the science!

  • Lovern Brown Lecointe

    Reply Reply March 6, 2015

    Hi, my number one discovery is the term Zonulin what it is and how it come about.
    2. It means to me that I can look use this knowledge to focus on the causes and understand symptoms as they are presented.
    3.Yes. I would use myself as a subject to determine why I have been having issues with my health, despite trying to eat healthy.This is in the role of specific foods and sleep debt.

  • kristene

    Reply Reply March 7, 2015

    I found this article a interesting read. I often find that when I have a lack of sleep or feel stressed, this directly affects my stomach and causes an intolerance to some foods.

    I also enjoyed the article on gluten. So many people I know opt for a gluten free diet because they feel that this makes them feel healthier. But I wonder, can it damage your body more by restricting gluten if you have no health issues related to this?

  • Natalie

    Reply Reply March 9, 2015

    I have Coeliac and you could say I prove the links exist as I have Fibromyalgia & Irritable Bowel. A flare up from ingesting gluten – never on purpose – causes me all manner of issues and a reaction in my Fibro status. I will see increased pain, inflammed joints/ankles/hands, brain fogginess and increases in dizziness and mood swings to name a few. Day to day these are relatively quick to pass, but after a bout of being ‘glutened’ the conditions increase to extreems and last for at least two weeks.
    Coping with the three conditions using dietry methods is nearly impossible as I have to accept that I can’t always find the best foods when away from home with work. Stress and sleep issues go hand in hand with Fibro so it is rather like a never ending cycle.
    The food of the Gods, as I call it personally, which means not messed around with by man & his machine is the easiest and simplist way to treat this daily in my experience. Irritable bowel negates some more of my choices as foods such as cucumbers/peppers/onion/garlic are off limits. This adds to the burden of being gluten free and I struggle constantly to find meals for a whole family that fit me too. It would help if I liked or could cook!! Maybe I should have studied cooking instead?
    Jucing veg and following a Paleo was marginally beneficial – although I know the academy hates protien based diets.
    leaky Gut may not sound terribly ‘educated’ but it is instantly understandable to any lay person which the other term – and i’m not going to try and spell it – isn’t. I’m not a doctor, not trying to be one. I will always use leaky gut.

    • Alex

      Reply Reply March 9, 2015

      Hi Natalie – thanks for your comment!

      Our research is unbiased and we don’t take a “position” or advocate any special “diet”, because everyone is different and what may work for you may not work for someone else. We believe it’s very important that our readers make their own decisions.

      We have doctors, dieticians, scientists, university professors and students who quote our reports and we want to facilitate their research into certain topics and make their citations easier.

      Whilst a term like “leaky gut” may be easier to remember, it’s overused and interpreted in different ways by different people who talk about it.

      There’s a lot of pseudoscience and bad science out there, so we have a very strict research and review process. It’s our responsibility to avoid junk science and deliver proven research to you. This way, when you share our content, you are spreading reliable, science-based information.

      You can learn more about our approach here: https://thehealthsciencesacademy.org/science-reports-premium-subscription/

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