SIBO diet — an evidence-based guide.
If someone has told you that you have SIBO, you have probably already been handed a great deal of instruction — cut all fermentable carbohydrates, cut fibre, cut sulphur-containing vegetables, stop snacking, take this herbal antimicrobial blend, then start again because the second test came back positive too. People often reach me having begun with bloating and unpredictable bowels and ended up somewhere worse: a very short list of permitted foods, anxiety around every meal, and no sense of whether any of it helps. That is exhausting, and it is not a sign that you followed the plan badly.
For deeper context, see: What to Eat Before, During, and After Your Workout (No Bro-Science, Promise).
Let me be straight with you, because there is a great deal of money in this corner of gut health. The science around small intestinal bacterial overgrowth is genuinely mixed — on how to test for it, on how often it explains someone's symptoms, and on what to do about it — and the confidence of the marketing does not match the state of the evidence. A SIBO diet can make you meaningfully more comfortable while the underlying problem is investigated, and that comfort is worth having. It will not clear an overgrowth by itself. One thing first: unexplained weight loss, blood in your stool, anaemia on a blood test, fever, or persistent vomiting are not symptoms to manage with a food list. Please see your doctor promptly if any of those apply.
What SIBO Is, and How It Differs From IBS
The small intestine is not meant to be a heavily populated place. Most of your gut bacteria live further down, in the colon, and the small intestine keeps its numbers low through stomach acid, bile, the ileocaecal valve, and — importantly for later — a sweeping wave of contractions that clears it between meals. Overgrowth is what happens when too many bacteria settle too far up. They ferment carbohydrate before you have absorbed it, and that produces gas where there is very little room for it: bloating soon after eating, visible distension, and bowels that swing between loose and sluggish.
The overlap with irritable bowel syndrome causes most of the confusion. IBS is a diagnosis of gut-brain interaction made on the pattern of your symptoms once other conditions have been excluded, and it requires no positive test of any kind. SIBO is a proposed mechanism — an excess of bacteria in the wrong place — that may explain some people's IBS-type symptoms. Some people with an IBS diagnosis do have an overgrowth driving it, and some people treated repeatedly for SIBO have IBS that would respond better to a properly structured low-FODMAP plan for IBS. Either way the symptoms are real, and they are not produced by a nervous personality.
Breath Testing and What It Can Honestly Tell You
Breath testing is the usual route to a SIBO diagnosis outside a hospital. You drink a sugar solution, you breathe into a series of tubes, and the laboratory measures the gases bacteria produce when they ferment it. It is non-invasive, inexpensive and easy to sell online. It is also considerably less accurate than the confidence of the report suggests.
The sugar has to travel through the small intestine to reach the colon, where a large and entirely normal bacterial population lives. If it travels quickly — and fast transit is common in exactly the people who get tested — the gas rise may be the colon behaving normally rather than the small intestine behaving abnormally. Preparation matters enormously and is frequently done badly: what you ate the day before, whether you smoked, whether you recently took antibiotics. Laboratories also use different substrates and different criteria for a positive result, so the same breath can be called positive by one provider and negative by another. [TK: confirm which breath test substrate and preparation protocol the doctors you work with use]
A breath test therefore belongs with a doctor who can weigh it against your history and rule out what mimics all of this — coeliac disease, inflammatory bowel disease, pancreatic insufficiency, thyroid disease. If a company sold you a kit and returned a positive result with a supplement protocol attached, you were sold a product rather than given a diagnosis.
Why Diet Does Not Eradicate SIBO, and What Needs Finding Instead
This is the part that disappoints people, and I would rather disappoint you honestly now than let you spend another year eating from a card. Food is the fuel bacteria ferment, so removing that fuel reduces the gas and the bloating, sometimes within days. It does not remove the bacteria. It quietens the symptom while leaving the population in place, which is why symptoms return so reliably when normal food does, and why people conclude they must restrict harder. Diet is a way of living comfortably while the real problem is found; it is not the treatment.
Antibiotics and herbal antimicrobials both belong with your doctor. Herbal products are medicines even when sold in a health food shop, and they interact with what you already take. I do not prescribe either, and I would be wary of anyone without prescribing rights who does.
The question worth pushing your doctor on is why the overgrowth is there at all, because SIBO is nearly always a consequence of something upstream:
- Motility that has slowed, whether after food poisoning, alongside long-standing diabetes, with an underactive thyroid, or for reasons never identified.
- Structural change in the bowel, including adhesions from previous abdominal or pelvic surgery, strictures, diverticula, or a removed ileocaecal valve.
- Medication effects, particularly long-term acid suppression, opioid painkillers, and drugs that slow gut transit.
- Systemic conditions, such as coeliac disease, connective-tissue disease affecting the gut, chronic pancreatitis, or previous bowel resection.
If nobody has looked for these, the overgrowth will keep returning however carefully you eat, and every positive retest will feel like your own failure. It is not.
Short-Term Symptom Diets: Time-Limited and Supervised
There is a legitimate place for a reduced-fermentation eating pattern while investigation proceeds. Cutting back the carbohydrates that ferment fastest often brings the bloating down enough that you can sleep, work and think about something else. I use this with clients regularly.
Three conditions make it safe. It must be time-limited, with a date for reintroduction agreed before you start. It must be supervised by someone monitoring your energy intake, fibre, calcium, iron and weight rather than only your bloating. And it must be one approach at a time. [TK: confirm how long you run a symptom-management phase before beginning reintroduction]
The stacking is what does the damage. Low-FODMAP on top of a bi-phasic protocol on top of low-sulphur on top of an elemental phase on top of no snacking leaves an eating pattern almost nobody can meet their nutritional needs on. What I see clinically is predictable: fatigue, poor iron and calcium intake, collapsed microbial diversity we then have to rebuild, and a slide into genuinely disordered eating. [TK: clinical observation — how often clients arrive already stacking two or more SIBO protocols]
So here is a plain rule to take away. If your food list has grown shorter at every appointment for months, something has gone wrong with the plan rather than with you. A diet that keeps narrowing is a warning sign, not progress.
Meal Spacing and the Migrating Motor Complex
Between meals, when your small intestine is empty, it performs a slow sweeping contraction that moves residue and bacteria downward towards the colon. Clinicians call it the migrating motor complex, and it is the gut's housekeeping cycle. It runs when you are not digesting and stops as soon as food arrives. Continuous grazing — a biscuit here, a handful of nuts there, milk in six coffees across a working day — means the sweep barely runs. For someone whose overgrowth is driven by sluggish motility, that matters more than any individual food on a list.
The practical version is unglamorous and free. Eat proper meals with real gaps between them, keep drinks between meals to water, tea or black coffee if milky drinks set you off, and protect the overnight gap between dinner and breakfast, which is the longest uninterrupted run the sweep gets. [TK: confirm the meal gap and overnight fasting window you advise]
One caution, because this idea gets pushed too far online. Meal spacing is not fasting and should never become cover for undereating — if you are hungry, eat. And if you have diabetes, are pregnant, or have any history of an eating disorder, meal timing needs planning with your doctor.
A Sample Day While Managing SIBO Symptoms
Here is what a symptom-management day can look like. Read it as an illustration rather than a prescription, and understand it as a temporary phase with a planned end. Your own version should fit your kitchen, your culture, your budget and your schedule.
- Breakfast: two eggs cooked as you like them, a slice of sourdough or a suitable gluten-free bread, olive oil or butter, and a few cherry tomatoes.
- Mid-morning: nothing, if you can manage a real gap, or a small handful of walnuts eaten as a proper pause rather than continuous grazing.
- Lunch: grilled chicken or tinned fish with rice, carrot and courgette cooked until soft, dressed generously with olive oil and lemon.
- Afternoon: tea or black coffee if they suit you, and water, with the gap protected rather than filled.
- Dinner: salmon or minced beef with potato, well-cooked green beans, plenty of olive oil, and a spoonful of lactose-free yoghurt.
- Evening: the kitchen closed, with the overnight gap protected.
[TK: confirm the meal gap and overnight fasting window you advise]
Notice how much food is in that day: protein at every meal, enough energy to get through work, fat for satiety, and vegetables cooked soft and peeled where it helps, in moderate portions rather than banned. Notice too that the structure is doing as much work as the ingredients — three defined meals, real gaps, a protected night. If you cannot get enough into you on a plan like this, the plan needs changing.
Widening the Diet Again, Which Is the Point of All This
Reintroduction is the part of SIBO care most often skipped, and skipping it is how someone ends up five years later eating nine foods. Your gut bacteria feed on the fibres and fermentable carbohydrates you have been avoiding, so extended restriction narrows the microbial community you depend on, as I cover in this guide to the gut microbiome, probiotics and prebiotics. Getting your food back is a clinical goal in its own right.
The method is slow and systematic. We reintroduce one food group at a time, in a modest portion, with a gap before the next, and we write down what happens rather than trusting memory. Some wind and rumbling is expected as fermentation restarts in a colon that has been underfed. We also separate the foods that genuinely reproduce your symptoms every single time from the ones you have simply become frightened of, because those two look identical from the inside and are handled very differently. If bloating stays your loudest symptom, my post on how to beat bloating and support gut health sits alongside all of this.
Common SIBO Myths
"If my breath test is positive, that explains all my symptoms."
A positive result tells you that fermentation happened, and it is easily produced by sugar reaching the colon quickly in someone with fast transit. It has to be read alongside your history, and coeliac disease and inflammatory bowel disease need excluding first, because they produce a very similar picture.
"I have to kill the bacteria off with a herbal protocol before I can eat normally."
Herbal antimicrobials are medicines with real effects and real interactions, and any decision of that kind belongs with your doctor. Buying a protocol online means treating a diagnosis nobody has confirmed, with a product nobody is monitoring, for a cause nobody has looked for.
"The stricter the diet, the faster I will get better."
The research does not support this, and my clinical experience runs firmly the other way. Restriction reduces gas because it removes the fuel, but it leaves the overgrowth in place while quietly reducing your fibre, your micronutrients and your microbial diversity.
"Bloating this bad has to be SIBO."
Severe bloating and visible distension are genuinely miserable and genuinely physical, and they have a long list of possible explanations: IBS, coeliac disease, constipation with retained stool, carbohydrate malabsorption, pelvic floor coordination problems, endometriosis, and gut hypersensitivity after an infection. SIBO is one item on that list.
"My SIBO keeps coming back, so I must be doing the diet wrong."
Recurrence usually means the underlying driver — motility, medication, adhesions, a structural change — has not been found and addressed. That is a reason to go back to your doctor with better questions, and it says nothing about your discipline.
Working With Hanzi Nutrition
I am a dietitian, and my honest position on SIBO is that most people arrive with too much restriction and too little investigation. My job is to help you eat comfortably enough to function while your doctor works out what is driving this, and then to give you your food back as fast as your gut allows.
At Hanzi Nutrition, I work fully online with clients across the Netherlands, Belgium, Germany, and Turkey, in both English and Turkish. We begin with a first consultation covering your symptoms and their timing, your test results and what they can reasonably support, your surgical and medication history, your current food list and how it got that short, and your relationship with eating, without judgement. From there I build a personalised plan through disease-specific nutrition therapy that fits your kitchen and your schedule, protects your energy, fibre, iron and calcium, and carries a written reintroduction plan from day one. If your history points towards a cause that needs investigating, I will say so plainly and coordinate with, never replace, your doctor. Then I stay with you through reintroduction, where most people are left alone.
If your food list keeps getting shorter and nobody has explained why, get a custom plan built to widen your diet safely and work alongside your medical care.
Hanzi Nutrition offers dietitian-led nutrition counselling across the Netherlands, Belgium, Germany, and Turkey, fully online, in English and Turkish. This article is general education and not a substitute for individual medical care. Breath test results require medical interpretation, and decisions about antibiotics, herbal antimicrobials, or any restrictive eating phase belong with your doctor. Please seek medical advice promptly for unexplained weight loss, blood in your stool, anaemia, fever, or persistent vomiting.
Related reading: Low-FODMAP Meal Plan for IBS · The Gut Microbiome, Probiotics and Prebiotics · How to Beat Bloating and Support Gut Health
Services: Disease-Specific Nutrition Therapy · Get your custom plan · Contact Hanzi Nutrition
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