About the author : victoriafenton

Those of you who read my first (lengthy) article (linked here) about the scientific background to SIBO, and then my second (much shorter) article (linked here) about carbohydrate aversion in relation to SIBO will know that this is a topic I could literally talk about forever.
But there is one thing I keep getting asked questions about which I slightly touched on in the second article but realistically is a topic in and of itself:

What diet should you eat when you have SIBO?
And is that for treatment, for prevention or for symptomatic relief?

Ahh… these question are, as with all things Functional Medicine, simultaneously very simple – and very complex.
The simple answer is, as always, it depends.
But if you’re reading this you don’t want to be fobbed off with answer that nutrition should always be personalised.  You want to know what it depends on.

The Patient Starting from Scratch with SIBO

The diet I recommend to my clients to tackle SIBO is definitely dependent on their current diet when they arrive in my clinic.
Because of the plethora of information on the internet I rarely see someone in my practice who hasn’t at least read a little about SIBO and the various dietary strategies.  Most have realised that they are struggling with some foods eliminated on one of these diets, self-diagnose as suffering with SIBO and attempt to follow said diet to ‘heal’.
On the rare occasion I see a patient with SIBO who has no idea what I’m talking about when I run a SIBO test, I never recommend that they immediately, drastically, cut all fermentable carbohydrates from their diet.  Some clinicians do, however I find that getting the testing done whilst the client is eating some of their symptomatic foods is actually a good place to start.
From there, when tests come back positive, I sometimes still don’t recommend a completely restrictive diet such as Low FODMAP (more on what this is later).  I find that for many it is too extreme – and I am cautious because any alteration of fermentable carbohydrates affects both small AND large intestine – which I don’t always want to do.  And sometimes complete elimination of every FODMAP is a unnecessary.  I know, that’s seemingly sacrilege in the SIBO world but for those who haven’t excessively restricted yet, reactions to all categories of FODMAPs is not something I’ve seen.
Instead, I ask clients like this to start food/symptom diaries – which they will give to me after a week.  From these I look at how their symptoms map to certain forms of carbohydrate and, without over-educating (or over-stressing) the client I can guide them to which group of the FODMAP foods seem to be excessively aggravating their symptoms.
I regularly find that just one or two of the FODMAP groups are problematic – and my knowledge is what can guide the patient to a highly specific, personalised diet, without them having to learn and remember a broad array of “legal” or “compliant” foods.  If you want to educate yourself, you can do this process yourself through looking at a FODMAP list after this initial diarising period.  It’s hard to do dispassionately though, as once you’ve looked into those lists they can be hard to forget!  Once you’ve started questioning food like this, it’s a slippery slope to suspicion over every food.  Which brings me to the more common client:

The Patient Already On A SIBO Diet

For those already on a specific diet when they consult me, they are usually following one of the following:
Low FODMAP: in this diet, Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols are minimised, though many forget that “low” does not mean “no” and look to eliminate all of these foods.
This is a huge array of carbohydrates that are eliminated as these carbohydrates feed bacteria, including those that have spread to the upper GI tract/small intestine (where they shouldn’t be, and when they’re fed they cause the characteristic SIBO symptoms).  You can take a look at a long list of FODMAPs here – but think wheat, dairy, a whole host of fruit and vegetables (including garlic and onions), spices, teas, artificial sweeteners, some nuts and seeds and prebiotic fibres.  The idea is to starve the bacteria by providing them with absolutely no fermentable fibres from any FODMAP foods.
Low FODMAP PLUS SCD (Dr Allison Siebecker):  this diet arose out of the recognition that those with SIBO regularly did not just have SIBO.  SIBO, as I said in my first Understanding SIBO article, is often a complication of other issues, or a part of the picture of complete GI dysregulation.  This means that yeasts and fungus, multiple sensitivities due to intestinal permeability and impaired digestion, enzyme and bile function regularly (if not always) go hand in hand with the development and progression of SIBO.  This diet combines the reduction of bacteria-feeding FODMAPs with the nourishing, gut-healing approach of the Specific Carbohydrate Diet.  It aims to remove the foods which cause both bacterial fermentation AND intestinal permeability.  It also assists with tempering any inflammation stemming from the gut.
Biphasic Diet (Dr Nirala Jacobi): this is getting increasingly popular because it takes the above diet and slots it into stages of reactivity that the patient can follow.  Starting incredibly restrictively it slowly reintroduces the most tolerated and least fermentable foods back in over a phase-in period.  This doesn’t change the foodstuffs included/eliminated, just provides the patient with more guidance as to how to embark on reintroductions and exploring their reactivities for themselves.
Fast Tract Diet (Norm Robillard): to my clinician’s eyes this just works on the same principles above but in a more numerical way.  To explain it requires explaining FODMAPs a little more:
As with so many things in physiology, the science of food fermentation is mostly dependent on load.  This is not about allergies or intolerances, it is about the symptoms created when higher amounts of food interact with the internal environment of the GI tract itself – the bacteria and yeasts within.  That means that whilst all FODMAPs do ferment, many people will be able to tolerate a certain quantity of fermentation before symptoms are experienced, or become intolerable.  This is why FODMAP toleration is load-dependent.
With small intestine bacterial fermentation we are concerned about the sugars and fibres of FODMAP foods.  The Fast Tract Diet is a sort of Weight Watchers for SIBO, in that it gives all of the fermentable carbohydrates a points value.  Your way to symptom-free living is to keep within the points value you know doesn’t cause you issues.  Each fermentable carbohydrate is scored and numbered, along with the values given for typical portion sizes (which is very handy).  The patient builds their diet from there.

In patients who arrive at my clinic on any one of these diets, elimination has already formed part of the backdrop to their life.  This means that the environment in their GI tract has already begun to change.  Therefore telling them to go back to eating foods they’ve removed (and often feel better for removing) is not something I am going to do.  Instead I work with the patient to understand their Gi system – how it has responded to their dietary manipulation, and what is and isn’t working.

What is The Purpose of the Diet?

The issue with the dietary recommendations for SIBO is twofold: firstly, diet is not treatment.  With the exception of employing an Elemental Diet,

You cannot get rid of SIBO through changing your diet alone.

Secondly, restrictions for SIBO can set us up for failure elsewhere.  It can cause further bacterial dysbiosis.  It can cause sensitivities to the foods we do eat repeatedly on these diets, and it can cause real challenges reintroducing the foods we have restricted.  
It can also become a crutch which we may have once needed to use, but are truly just too scared to let go of.


Treatment for SIBO is antibiotics, whether herbal or pharmaceutical, alongside diet, prokinetics and probiotics.  Not all at once, nor all as strict or drawn out for everyone.  And they don’t all work as well as one another all of the time.  But there is a combination approach to treatment.
The only time that diet is a treatment for SIBO in and of itself is when an Elemental Diet is used to treat SIBO.  This is NOT what most of my clients are doing, or choose to do – though it is possible and is an effective treatment option.
So what is the diet-portion of SIBO treatment achieving?
Well it’s basically decreasing the fuel for the reproduction and proliferation of the bacteria which you are trying to kill.  Bacteria need the substrate of fermentable carbohydrates to replicate and spread.  Starving the bacteria, or at least removing a good portion of the fuel, means that they are both somewhat easier to get rid of with the treatment, but also that the symptoms of fermentation are minimised.
It is this symptomatic improvement which I worry about with SIBO diets.  Feeling better when eating such a low variety of foodstuffs has never equalled healing to me.  I also have many clients for whom slow transit and subsequent SIBO was the net result of an eating disorder.  Therefore recommending restriction can, for some, be a direct trigger back into a dangerous mental space around food.
But the reality is that for those who have dealt with SIBO for a long time, food is an enemy anyway.  For reasons beyond emotional and mental illness, relationships with food can swiftly become negative when every time you eat there is some degree of discomfort, swelling, pain and stool inconsistencies.
Diets can therefore be empowering, because they feel like you are claiming some control back over your body and your pain.  And yet, they are not tackling the problem.


Where diet does play a role in tackling the problem is when it comes to prevention.  SIBO can be recurrent in those with typically slow transit, abdominal adhesions (scar tissue from old wounds, accidents etc.), a slowed migrating motor complex due to post-infectious immune attack of the Interstitial Cells of Cajal (see my first article if this is lost on you), or (as in my case) connective tissue disorders.
All of these predispositions mean that slipping back into struggling with SIBO is easier.  In these cases, a relative care over consuming excessive fermentable carbohydrates is called for, alongside taking prokinetics and probiotics (for the large intestine).  This can be lifelong.
But this does not in any way mean that the strictness of the Low FODMAP, Siebecker, Jacobi or Robillard diets should be stuck to long term.  With the possible exception of the Fast Tract diet, providing you adjust tolerability values as you improve, these diets in their purest form are too restrictive to be sensible when used long term.

What Are the Risks of the Diet?

Yes, there is a suggestion that long term use of a low FODMAP diet can affect large intestine gut bacterial diversity.  But personally, I am more worried about the psychological crutch of food restriction and manipulation.
When we have witnessed our body go from symptomatic to symptom-free we often want to stay in the ‘safe’ place.  When we have watched a specific food cause such bloating and distention we are often reluctant to modify our attitude towards that food.  Eating becomes such a stress that the security blanket of a food-limited diet becomes attractive.
And yet it is a deep burden: psychologically, emotionally and physically.  It affects social isolation, it becomes traumatic in and of itself – and worse, such limited calls on our digestion can alter our ability to tolerate anything else.  Once only mildly symptomatic when ingesting a food, long term elimination of that food can mean that the slightest introduction of it causes dramatic symptoms so the patient backs away entirely.
This is very similar to helping anorexic patients to eat again.  I have witnessed the trauma that occurs when this is done inappropriately.  Because the body is so unfamiliar with digesting certain foods the symptom flare initially is always extreme – with bloating, swelling, flatulence and indigestion all playing a role.
The same can happen with SIBO patients if the reintroductions aren’t done carefully.  And this is why recovering from SIBO, particularly when restrictive diets have been used, can be such a psychological battle.

Moving clients from a place of eating only five foods, up to a diet filled with nourishing variety is such a large part of my work with SIBO.  Treatment is relatively easy, compared to this task.  Expanding the ability to tolerate broader and broader food groups/types can be so challenging when every mouthful has been hellish for such a long time.  The process can be slow, the support needed extensive – but the reward is that you get to help your GI tract evolve to digest, enjoy and gain sustenance from a wide variety of nutrition.

So How Do These Warnings Help With Diet Choice?

This hasn’t been too useful thus far in helping anyone choose their SIBO diet.  The truth is that I am actually fairly agnostic when it comes to the choice, simply because the best diet is the one that works for you.
And yes, this requires experimentation and trying things out.
Part of my work, in the early stages of SIBO, is preparing my clients for the fact that I am going to get things wrong some of the time.  Accepting failure, and the symptoms that come with trialling a food that you react to, is part of this process.
And yet, I am always keen to express that you cannot ‘break’ any treatment protocol by eating a FODMAP that you feel caused symptoms.  In fact, some camps in the SIBO world (namely Pimental) insist that feeding the bacteria with FODMAPs forms part of a healthy, holistic approach to this issue.  Being bloated isn’t a failure of you in sticking to a diet, it’s a reflection that there is still work to do in the small intestine.

Therefore, the best diet is the one that you can stick to, as with any healing protocol.  But it is also the one that makes you feel confident and able to tackle your GI issues.

What you choose largely depends on how your brain works – because the diets are much of a muchness in the foods they restrict.  If you like numbers and calculations – Fast Tract.  If you like feeling like you’re on a process/journey/staged diet – Biphasic.  If you do well with boundaries, rules and hard lines – Low FODMAP PLUS SCD.
And if you know that there’s just a few of those pesky FODMAPs that make you feel rubbish – simply stop eating those ones for a while and create your own beautiful, personalised, nutritional template.
More than this, the best diet is the one that can be embraced as a temporary intervention to assist with a what should be a short term strategy.  Going into restriction knowing that the next step is slow expansion and self-experimentation is an empowering way to view the dietary manipulations which support SIBO treatment.
Even if you are someone for whom SIBO is a fairly constant background, you will discover that there are foods that you are fine with, even though they appear on a list somewhere.  You will also discover that you have levels of tolerability, which may or may not tally with those on any of the diets.  You may have days where one sweet potato was too much, and days where that is fine, but throughout it you will be learning about your body and what makes you feel good.  And it will change.  As your treatment works, your digestion will alter.  True success lies in the ability to adapt.
So yes, diet is important for SIBO, but no it is not the be all and end all.  As for which diet?  Well … because of all the reasons listed above, I return to the really simple answer: it depends.
If you’re struggling and need someone to oversee your SIBO treatment – holistically looking at all aspects of tackling SIBO itself AND understanding why it cropped up for you – please just get in touch with me today and I’ll be delighted to help.


  1. Katherine Bruno February 8, 2018 at 2:01 am - Reply

    As a Registered dietitian specializing in eating disorders I SO appreciate this article! Many of my patients find themselves with GI issues (esp SIBO) after falling into the pit of their illness and then are so scared to eat anything even though their recovery requires it. This can often feel like a losing battle and with all the extreme info on the Internet it’s such a breath of fresh air to be able to pass your message along to them. Thanks again for your insights and expertise!

  2. Jacqi February 26, 2018 at 5:03 pm - Reply

    I’ve been on the biphasic diet for almost a week for treatment of SIBO, along with several supplements prescribed by a physician. My question is, can I have fresh tomatoes or red, yellow and orange peppers? When looking at the biphasic diet, it says tomatoes/sundried. I’m not sure if that means only sundried or not. I know tomatoes have fructose in them so I’m just looking for clarification. Thank you.

    • victoriafenton February 28, 2018 at 2:51 pm - Reply

      Hi Jacqi – tomatoes are typically fine for those with SIBO. Sun-dried tomatoes are moderate FODMAPs so you can have around 2 Tablespoonfuls (15g) without triggering things. Dr Jacobi classes both as fine – from experience, I know that tomatoes in cooked/puree state are pretty aggravating and sun-dried tomatoes can be too concentrated, so go easy. Peppers themselves are fine to eat. Best, Victoria

  3. Simon May 28, 2019 at 7:07 pm - Reply

    HI, great article thanks. I’m following the bi-phasic diet at the moment. I’m one week in and I have lost 4lbs weight. Any easy suggestions for keeping the weight on. I’m eating lots of meat and up to 4 eggs a day. I find oils/fats difficult as they cause reflux. Also, what are the guidelines for nuts/seeds? This part of the diet sheet confuses me..
    Many thanks

    • victoriafenton June 16, 2019 at 11:52 pm - Reply

      Hi Simon – sorry for a delay here, your comment was strangely spammed by my system! You are right that the bi-phasic diet is tricky to follow because it does cause weight loss – how are you doing now? I never recommend the bi-phasic diet for SIBO to any of my patients. Whilst it offers symptomatic relief, I don’t feel that it is therapeutic in and of itself. I also cannot guide you specifically as you are not my patient – I suggest that you chat with your practitioner about their rationale for this diet in your case, whether it is strictly necessary – and if you’re not working with someone, you really need to be in order to ensure that the diet is nuanced to you such that you don’t drop any weight unnecessarily. Best wishes, Victoria

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