Small Intestine Bacterial Overgrowth (SIBO) – is it contributing to your IBS?

Irritable Bowel Syndrome (IBS) is a collection of unpleasant symptoms associated with the digestive system which affects approximately 10 million people in the UK. IBS is considered to be an uncomfortable yet non-life threatening condition, and has been identified as a trigger for many other more serious conditions.

As many symptoms of IBS are non-specific it can be difficult to identify the root cause of the condition and can often be attributed to many aspects of digestion which are not functioning optimally.

An individual with IBS may experience bloating, abdominal pain, flatulence, constipation, diarrhoea and be constantly trying to identify foods that trigger symptoms. Studies show that at least 50% of patients diagnosed with IBS have small intestine bacterial overgrowth (SIBO) therefore supporting the health of the small intestine should be considered for IBS suffers.

What is SIBO?

In a healthy individual, the small intestine, whilst not necessarily completely sterile, should have a very low content of bacteria (the important gut flora that are talked about frequently are found in the colon). SIBO occurs when bacteria colonise the small intestine and then overgrow. These bacteria can then ferment dietary sugars and carbohydrates which leads to a build-up of gas and can then cause symptoms of bloating, pain and flatulence.

These bacteria are also able to de-conjugate bile acids from fat (bile is essential for emulsifying fat to allow it to be absorbed); this can lead to poor fat absorption and therefore deficiency of essential fatty acids and fat soluble vitamins (i.e. vitamins A, D, E and K) as well as diarrhoea caused by excess fat in the stool.

It is also associated with B12 deficiency as the bacteria can remove B12 from intrinsic factor which is required for B12 absorption. Prolonged SIBO can potentially initiate further damage to the small intestine leading to malabsorption and potentially the onset of leaky gut, again a trigger for systemic disease. You can find a link to our previous blog on ‘leaky gut’ here.

What causes SIBO?

Like IBS the causes of SIBO seem to be multi-faceted but have been mainly attributed to:

Low stomach acid – hydrochloric acid in the stomach plays many roles, one of which is to sterilise food that has been consumed. If stomach acid is low then excess bacteria can enter the small intestine and colonise there.

Low motility – the movement of the gut is known as peristalsis, this transports the bulk of food but also help to move bacteria through the digestive system as well. If motility is low, which is consistent with constipation, the bacteria present has an opportunity to migrate from the colon to the small intestine.

Other factors associated with SIBO are;

  • Low pancreatic (digestive) enzymes
  • Poor immune function
  • Previous bacterial infections

It is important to address these underlying causes but doing this alone will not eradicate SIBO, this is discussed in more detail later.

How is SIBO identified?

Symptoms that are associated with SIBO are:

  • Gas, bloating and flatulence
  • Diarrhoea
  • Abdominal cramping
  • Fat in the stool (stools may have a pale and oily appearance and often float)
  • Intolerance to lactose (sugar found in milk)
  • B12 deficiency (megaloblastic anaemia)

If these signs and symptoms are seen (particularly in combination) SIBO can be suspected. However there are simple breath tests available to identify the production of hydrogen or methane, which are produced through the fermentation of lactulose by the bacteria in the small intestine.

Dietary and Supplementary interventions for SIBO

There are dietary and supplement interventions that can specifically support individuals with SIBO, which are outlined below. It can also be beneficial to follow a 4R programme in order to fully rebalance and repair the digestive system, this is identified in our Cytoplan blog: Nutritional support for Irritable Bowel Syndrome.


FODMAPs are dietary sugars and carbohydrates which are easily fermented by the bacteria and can exacerbate symptoms of gas, bloating and pain. Therefore it is often very useful to remove them from the diet.

FODMAPs stand for:


Oligosaccharides (e.g. Fructans found in wheat, garlic, onion and chicory etc. and Galactans found in legumes; including beans, peas and lentils.

Disaccharides (e.g. Lactose found in milk products)

Monosaccharides (e.g. excess Fructose found in fruits, honey, high fructose corn syrup etc.)


Polyols (found in sweeteners containing isomalt, mannitol, sorbitol, xylitol plus stone fruits such as avocado, apricots, cherries, nectarines, peaches and plums.)

After excluding high FODMAP foods for a month, foods from each FODMAP group should be reintroduced, one at a time (e.g. foods containing fructose, then foods containing lactose etc.).

During the reintroduction symptoms should be monitored and if a FODMAP group of foods causes problems then continue to eliminate this group. It should be noted that avoiding FODMAPs will not remove SIBO but help modulate the symptoms.

Please note that a low FODMAP diet involves initially restricting a considerable number of foods which some may find very difficult; however it is not intended to be a long-term diet and because of the restrictive nature and complexity it is best to be followed with the guidance of a practitioner.

Remove bacteria from the small intestine

Primarily, the main intervention for SIBO needs to be the removal of bacteria, as merely addressing underlying causes and avoiding foods which are exacerbating symptoms will not be enough.

Natural antimicrobials can be useful for removing bacteria from the small intestine. These include:

Caprylic Acid – a natural dietary fatty acid which assists in the maintenance of normal intestinal micro-flora and can help inhibit the growth of opportunistic fungi such as candida albicans.

Garlic – long standing use as an anti-microbial

Oregano extract – broad spectrum anti-microbial activity.

Grapefruit Seed extract – research shows evidence for anti-bacterial activity against gram-positive and gram-negative bacteria.

Green Tea Extract – anti-bacterial and anti-fungal activity.

It is always advisable to take a live bacteria supplement along with and anti-microbial (although take at least 2 hours apart from each other) as this helps to ensure a healthy colonisation of gut flora in the large intestine.

You can find links to our recommended Cytoplan products at the end of this blog.

Address the underlying cause

Low stomach acid

If stomach acid is low this needs to be addressed as there will be a risk of SIBO returning following anti-microbial use if stomach acid insufficiency persists. Symptoms associated with low stomach acid are:

  • Poor appetite in morning
  • Undigested food in stool
  • Bloating and /or pain shortly after eating (30 minutes)
  • Heartburn and reflux
  • Suspected malabsorption or nutrient deficiencies

It is also possible to test hydrochloric acid levels by consuming a ¼ teaspoon of bicarbonate of soda in and small glass of water, then timing how long it takes to belch. If it takes longer than 5 minutes (it should happen within 2-3 minutes) this indicates that levels of hydrochloric acid are low.

You can support stomach acid levels by:

  • Supplementing with Betaine Hydrochloride just prior to meals
  • Ensuring adequate zinc levels (zinc is important for production of stomach acid)
  • Avoiding drinking large quantities of water 30 mins before and during meal, as this can dilute stomach acid.

Poor motility

If motility is low this will be seen in conjunction with constipation as there is limited movement of the bowel. It is important for many reasons to help initiate peristalsis (bowel movements) as well as reducing likelihood of SIBO and constipation can often also be seen in IBS patients who do not have SIBO.

Gut motility can be supported by:

  • Obtaining at least 1.5-2 litres of water per day
  • Consuming soluble and insoluble fibre from vegetables, fruits and moderate amounts of wholegrains
  • Taking a live bacteria supplement
  • Taking a magnesium supplement (magnesium is involved in muscle relaxation)
  • Gentle exercise

Low pancreatic (digestive) enzymes

If digestive enzymes are low, larger molecules can sit in the small intestine for longer periods of time and be more prone to fermentation which can exacerbate IBS symptoms. There are tests available to determine digestive enzyme function, but in cases of SIBO it is likely that digestive enzyme function is already somewhat impaired and therefore supporting pancreatic enzymes as well as bile production, in the short term, can aid symptom relief and repair.

You can support pancreatic and digestive function by:

  • Taking a digestive enzyme supplement with meals
  • Consuming bitter foods (lemon, rocket, chicory, watercress) which stimulate bile secretion
  • Obtaining phospholipids from diet or as a supplement to aid fat emulsification


If all of these suggestions are used in conjunction with each other they can be effective against SIBO. However it should be noted that, although many patients with IBS may have SIBO, there are often other functions of the digestive system that also need support, so it is advisable to look at the health of the gut overall. SIBO can often be seen alongside dysbiosis (an imbalance of flora in the colon) and leaky gut (damage to the to the gut mucosa, allowing larger molecules to enter the blood stream triggering inflammation). For more information about IBS and leaky gut see Cytoplan Blog: Nutritional Support for Irritable Bowel Syndrome and Leaky Gut Syndrome: The Signs and Symptoms.

Relevant Cytoplan Products

Caprylic Acid Plus – Anti-microbial supplement containing Caprylic Acid, Garlic, Oregano Extract, Grapefruit Seed Extract and Green tea Extract.

Cyto-Zyme – Digestive enzyme and Betaine HCl supplement.

Betaine & Pepsin – contains digestive enzyme pepsin to aid protein digestion and Betaine HCl.

Acidophilus Plus – Live bacteria Supplement containing 9 strains of bacteria

Saccharomyces Boulardii – a unique bacterial yeast that has been safely used worldwide to support intestinal health for more than half a century.

Biofood Magnesium – Food State magnesium supplement.

If you have any questions regarding the health topics that have been raised please don’t hesitate to get in touch with me (Amanda) via phone; 01684 310099 or e-mail (

Amanda Williams and the Cytoplan Editorial Team: Helen Drake and Joseph Forsyth.


4 thoughts on “Small Intestine Bacterial Overgrowth (SIBO) – is it contributing to your IBS?

  1. Hello. I can relate to a lot of the symptoms I`ve just read. I`ve suffered with constipation since my mid twenties and i`m now 47. The bloating started in my 30`s and now pretty much everything I eat causes my stomach to bloat. Recently I`ve been resorting to laxatives/suppositories to try and help empty my bowels. I have tried natural tablets and supplements but have found that over time they stop working.
    I also have insomnia and daily migraines so things get tough at times. I had a colonic treatment 2 wks ago and had a good clear out, I felt amazing!! Unfortunately things returned back to normal soon afterwards, even with the recommended diet adjustments that had been suggested. I’m due to have another colonic next week.
    I use Cytoplan for my supplements and I called yesterday asking for advice on vitamin C and magnesium re constipation. Unfortunately there were no Nutritionists available until Monday.
    I would love to hear from anyone who can advise and point me in the right direction please. These symptoms have baffled me and many others that I’ve been seeking help from. As you can imagine, they are difficult and uncomfortable to live with and have a huge impact on my life.
    Sorry the message is so long, but I’m at a desperate stage with all of this and just wanted to try and make it clear on what kind of help I may need.
    Looking forward to hearing from you!
    Many thanks.

    1. Hello Nandi,

      Thank you for your email query. I am sorry you were unable to speak to a nutritionist when you called. We have someone available Monday to Thursdays 11.30 to 3.30 pm. You may be interested in our free health questionnaire service – if you complete and return a health questionnaire we will send you some written diet and supplement recommendations specific to your health concerns. Please get in touch for further details.

      In the meantime, some more general advice relating to constipation:

      – Flaxseeds can be useful, either whole seeds (soaked for a few hours and then eaten with the soak water) or ground and sprinkled on food. Start slowly ie 1 teaspoon per day and increase gradually to 1 to 2 tablespoons
      – Psyllium husk – again these are high in fibre. It is really important to take psyllium with sufficient liquids. Start slowly with 1 teaspoon and can be increased up to 4 teaspoons per day
      – Live bacteria eg Acidophilus Plus – 1 – 2 capsules per day, on an empty stomach
      – Aloe Vera Inner Leaf gel – dose according to weight, as per instructions
      – Adequate hydration and exercise are important
      – If you are bloating then I would consider including a digestive enzyme with hydrochloric acid
      – There may be foods that are triggering the problem. In particular I would start with taking gluten out of your diet. However, be aware that gluten foods provide most of the fibre intake in the average diet (>70%) so if you remove this and swap to gluten free products your diet may become very low in fibre. Good sources of fibre include vegetables, fruit, nuts/seeds (baked or stewed apple with skin is effective for some people). Aim to have half plate lightly steamed, non-starchy vegetables at each meal.
      – If the above suggestions do not help with bloating then a FODMAP elimination would be something to consider – we have written about FODMAPs on a separate blog
      – High dose vitamin C and magnesium that you ask about can have a laxative effect, for a laxative effect the doses may need to be quite high, so I would start with the other recommendations
      – Vagus nerve exercises – the vagus nerve connects the brain to the gut and stimulating the vagus nerve may be helpful. This can be done by singing (loudly), stimulating the gag reflex in the mouth and gargling. It needs to be done daily, gradually increasing the amount of time

      With regard to insomnia, there are many possible causes and it is useful to identify these in order to know how best to support. Do you have problems getting to sleep or staying asleep? Are you experiencing high stress? For some people nutrient co-factors that support melatonin (sleep hormone) synthesis can be useful. For others nutrients that aid relaxation and support synthesis of GABA (the calming neurotransmitter) are important. Low blood sugar during the night can be another cause for middle of the night waking.

      These are some ideas and you may already have tried some of them. If you complete a health questionnaire we can have a look a bit closer at factors that might be contributing to constipation / bloating and insomnia and make some relevant recommendations.

      I hope this helps.

      All the best

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