Nutrition For SIBO: What Do I Need To Know? | The PNW Clinic

Are you worried you may have SIBO? Whether you have been diagnosed or have just heard about SIBO, it can be difficult to get reliable and factual information. Here’s what our online dietitians in Australia have to say regarding what SIBO is, everything you need to know about it, and nutrition for SIBO that could help aid your digestive symptoms. 


What is SIBO?

SIBO stands for small intestinal bacterial overgrowth. It’s characterised by abnormal amounts of bacteria located in the small bowel. 

The digestive tract is naturally home to trillions of bacteria. However, most of these bacteria are found in the large bowel. The small bowel normally only contains small amounts. When bacteria from the large intestine overflow into the small intestine, it can disrupt normal digestive processes. 

In particular, SIBO is known for causing disruptions to the proper absorption of vitamins and nutrients [1]. Nutrition for SIBO is an important issue to address as a lack of vitamin and nutrient absorption can result in deficiencies which can lead to poor health. 


SIBO symptoms 

The commonly reported symptoms of SIBO include [2]: 

  • Diarrhoea 
  • Abdominal pain/discomfort
  • Bloating 
  • Flatulence 
  • Urgency 
  • Nausea 

Sound familiar? These symptoms are very common and non-specific. This means the symptoms overlap with many gastrointestinal disorders and irritable bowel syndrome. Any changes in bowel habits should be discussed with your doctor as further investigations may be required. 


bloating and nutrition for ibd on a plant-based diet


SIBO diagnosis

There is no gold standard yet for diagnosing SIBO. Diagnostic testing usually involves breath testing as it is safe and non-invasive. Glucose and lactulose breath tests are the most common tests used to detect this condition [1].  


How does a breath test work?

Preceding the test, sugar (lactose or glucose) is ingested. Bacteria then ferment the sugar and produce hydrogen and methane gasses as a result. These gases get absorbed across the digestive tract and carried into the bloodstream. The gases are then transported to the lungs where the gas is exhaled and the breath is collected. High levels of these gasses detected in the breath will indicate increased bacterial activity. 


Is breath testing reliable?

Breath testing has its flaws, and as such a diagnosis of SIBO should not solely rely on results from breath testing. Breath testing is not a standardised method, meaning it isn’t performed consistently. It can also produce false positives in some digestive disorders in which your gut transit time is accelerated. 


Who is at risk of developing SIBO?

While it is unknown how common SIBO is amongst healthy people, researchers have determined that the causes of this condition generally involve [1]:

  • Lack of stomach acid
  • Changed gut motility
  • Structural changes to the digestive tract
  • Impaired immune system

Some health conditions or lifestyle choices may increase your risk of developing SIBO: 

  • Older age 
  • Irritable Bowel Syndrome
  • Crohn’s disease 
  • Diabetes 
  • Chronic pancreatitis 
  • Coeliac disease
  • Renal failure 
  • Chronic intestinal pseudo-obstruction 
  • Small intestine diverticula 
  • Surgeries including: Blind intestinal loop, resection of the ileocecal valve, and total colectomy or ileostomy 
  • Medications: Chronic use of antacids 
  • Lifestyle: Chronic alcohol abuse 


Nutritional risks of SIBO 

If left untreated, the long term effects of SIBO can have some serious consequences: 

  • Unintentional weight loss
  • Malabsorption of vitamin B12 and iron which can cause anaemia
  • Malabsorption of protein (hypoproteinemia)
  • Steatorrhea (fat malabsorption) which may also result in deficiencies in fat-soluble vitamins (A, D, E, K)


green leafy vegetables are important to boost fertility on a plant based diet


How is SIBO medically managed?

If you suspect you have SIBO, you should consult your doctor to undergo appropriate diagnostic testing and treatment that addresses nutrition for SIBO. Management involves correcting the underlying cause, antibiotics to reduce small bowel bacteria and addressing nutrient deficiencies [1].  


1. Correct any possible underlying cause 

Radiographic imaging should be performed to investigate the underlying reason for SIBO and then correct it if possible. Any underlying structural causes of this condition should be corrected through surgery. For example, to fix strictures, fistulas, diverticulums or blind loops. Impaired bowel motility or stomach acid can be treated with prokinetic agents (medications that help gut motility). 


2. Antibiotics 

Antibiotics may be prescribed by your doctor to treat SIBO. Antibiotics work by killing the bacteria or stopping them from multiplying. Rifaximin (a type of antibiotic) has been shown in multiple studies to be a safe and effective treatment [3]. However, the recurrence rate of SIBO after undergoing antibiotic treatment is high. Evidence shows that 30% of individuals treated with rifaximin had a recurrence of the same condition 6 months down the track [4]. To limit the overuse of antibiotics, changes in lifestyle and diet management are important.


3. Correct nutrient deficiencies and dietary management 

Low levels of vitamins A, D, E, or B12 can be identified through a blood test with your doctor. If any nutritional deficiencies are found, they should be replaced through dietary management. Working with an online dietitian in Australia can help you make sure all your nutritional needs are met. A dietitian can also work with you to come up with personalised diet strategies to help manage your digestive symptoms. 


Dietary strategies to manage SIBO

Currently, there is no specific prescribed diet for managing SIBO. However, if you have SIBO, you are likely to benefit from eliminating high FODMAP foods. 

FODMAPs are short-chain carbohydrates (sugars) found in a range of foods. These sugars normally provide a source of fuel for gut bacteria which helps them thrive, however in people with SIBO, eating FODMAPs results in excess gas production from these bacteria.

There are numerous studies that suggest the low FODMAP diet is effective at managing IBS and Inflammatory Bowel Disease (IBD) [5]. There is not enough evidence to say that the low FODMAP diet is effective for managing SIBO specifically, but many of the symptoms of this condition overlap with IBS and IBD, so those with SIBO may find symptom relief from following a low FODMAP diet.  

Some high FODMAP foods to be mindful of: 

  • Apple, mango, dried fruit, peach, nectarine, plum, watermelon, pear, fruit juice 
  • Garlic, onion, leek, artichoke, asparagus, mushroom, cauliflower, eggplant, snow peas
  • Wheat bread, rye bread, barley
  • Red kidney beans, felafels, baked beans, split peas, vegetarian mince 
  • Cashews, pistachios 
  • Cows milk, sweetened condensed milk, evaporated milk, ice-cream, soy milk (from soybean), custard
  • Honey, high fructose corn syrup, sugar-free confectionary, agave syrup 


Vegan Low FODMAP Diet - Foods To Avoid, Recipes, Symptoms


It is important to note that the elimination phase of the diet should not be followed long term. The low FODMAP diet restricts plant-food diversity which can be detrimental to your gut health. For more information on low FODMAP foods, read nutrition for IBS on a plant-based diet.

The low FODMAP diet is complex and involves a number of phases. It is also restrictive so it should be carefully followed under the guidance of an Accredited Practising Dietitian (APD). All of our dietitians at The PNW Clinic are trained in the low FODMAP diet by Monash University. 

The low FODMAP diet is not appropriate for everyone. This type of restriction may be harmful for people who are underweight, have experienced a past or present eating disorder, have a poor relationship with food or have certain medical conditions.

Some other dietary strategies that may help:

  • Eating small meals more frequently
  • Be mindful of carbonated beverages, chewing gum, drinking through a straw and artificial sweeteners (e.g. sorbitol, aspartame, and saccharine) as they can exacerbate bloating and flatulence.


Should I take a probiotic for SIBO?

Probiotics are bacteria that provide health benefits when consumed. Probiotics provide benefits by crowding out bad bacteria to create a balanced gut flora. 

You may be thinking, why treat bacterial overgrowth with additional bacteria?

Evidence shows probiotics have been beneficial in reducing and relieving some symptoms of SIBO [6]. Unfortunately, they have not been shown to be effective at preventing this condition. Probiotics could be something to consider as part of your treatment after trialling antibiotics and nutrition for SIBO through the low-FODMAP diet. 


Considerations for managing SIBO on a plant-based diet

The low-FODMAP diet can be very restrictive during the elimination phase. Thus, being plant-based or vegan may restrict food options even further. 

Without careful planning, this over-restriction might compromise diet variety and nutrient intake. Specific nutrients that are commonly missed on a low-FODMAP plant-based diet are B vitamins, iron, calcium and dietary fibre. 

It is recommended to work with an online dietitian in Australia such as one of our team members at the PNW Clinic to help you develop a plan that ensures your nutrient needs are being met. 


What other dietary and lifestyle strategies can help manage SIBO?

The Specific Carbohydrate Diet (SCD) 

The SCD requires you to eliminate particular carbohydrates from your diet. It has been shown to ease symptoms of digestive disorders like IBD [7]. As a result, it is thought to also help with SIBO symptoms. 

The SCD restricts all grain foods, sugar, starchy vegetables, some legumes and most milk products. 

This diet is even more restrictive than the low FODMAP diet and has limited evidence to prove effectiveness for SIBO management. Until we know more, the SCD is not recommended until after trailing antibiotics and a low FODMAP diet. 


The Elemental Diet 

An elemental diet is where all food is replaced with liquid supplement drinks which provide complete nutrition (i.e. meet all energy and nutrient needs). These liquid formulas are used to give your digestive system a ‘break’ from digestion and reduce inflammation. 

One study showed correction of lactulose breath tests and significant improvement in digestive symptoms in 80% of participants with IBS after following a 2-week elemental diet [8]. This study was conducted with people with IBS with abnormal lactulose breath test results. After the 2-week trial of the elemental diet, 74 of the 93 participants normalised their lactulose breath test results. It is important to note that lactulose breath testing is not a reliable tool to detect SIBO, so this approach has its limitations. 

The elemental diet is not suitable for everyone and should only be done under the guidance of your doctor and dietitian. 


Regular Movement 

Regular physical activity has positive effects on gut motility. A common cause of SIBO is slowed gut motility (i.e. failure to clear the bowels regularly). Adding 30-45 minutes of moderate activity into your daily routine will help prevent this by promoting regular bowel movements [9].  



Small intestinal bacterial overgrowth is a poorly recognised condition and can be misdiagnosed. Evidence supports the use of antibiotics which should be followed up with dietary management addressing nutrition for SIBO for effective treatment.

Dietary management may involve correcting nutrient deficiencies and following a low FODMAP diet (if appropriate) to ease symptoms. We recommend booking in with one of our dietitians to personalise these strategies to your individual needs. 


Article written by: Student Dietitian Shauna Gibbons

Reviewed by: PNW Clinic Dietitian Megan Boswell