In the intricate world of gut health, two often misunderstood conditions stand out: Small Intestinal Bacterial Overgrowth (SIBO) and Small Intestinal Fungal Overgrowth (SIFO).
SIBO and SIFO not only sound similar, they have similar symptoms including bloating, gas, and abdominal pain. No wonder people get them confused!
While these conditions both affect your gut – and the small intestine in particular – they are not in fact the same thing. In order to return your gut to optimal health, you first need to understand the difference between the two.
In this blog, Boulder Holistic Functional Medicine in Boulder, Colorado, explores the difference between SIBO and SIFO. We will look at how you can use functional medicine to diagnose, manage, and treat these gut dysfunctions, with specific emphasis on the role your diet plays in managing these conditions.
Understanding SIBO and SIFO
Like we said before, SIBO and SIFO both affect the gut and have similar symptoms. It’s the cause that sets them apart.
SIBO is caused by an overgrowth of bacteria and SIFO an overgrowth of fungus (typically yeast).
Both disrupt the gut but require unique treatments and management, which is why a proper diagnosis is so essential. Let’s look a little closer at the difference between SIBO and SIFO, including common symptoms and causes.
What is SIBO?
SIBO, or Small Intestinal Bacterial Overgrowth, occurs when there is excessive bacterial growth in the small intestine, a condition that disrupts the normal microbial ecosystem. This imbalance can lead to a variety of gastrointestinal symptoms such as bloating, gas, diarrhea, constipation, and abdominal pain.
The causes of SIBO are multifaceted, often linked to issues like slow intestinal motility, structural abnormalities in the gut, prolonged proton pump inhibitor use, or certain medical conditions.
What is SIFO?
SIFO, or Small Intestinal Fungal Overgrowth, is less commonly discussed and shares similar symptoms with SIBO. It involves an overgrowth of fungal organisms, primarily yeast, in the small intestine.
Factors contributing to SIFO can include prolonged use of antibiotics or steroids, weakened immune system, mold exposure, or dietary imbalances.

The bacteria in SIBO and fungus in SIFO disrupt the balance of your microbiome. So not only do you have to deal with the uncomfortable symptoms of gut dysfunction, but many of the body’s other systems are thrown out of balance as a result. A healthy microbiome is essential for immune function, energy, and even mental and emotional health.
You can read more about causes of gut dysfunction and the importance of the microbiome in this article here.
Both SIBO and SIFO can significantly impact one’s quality of life which makes it even more crucial for you to get a proper diagnosis and individualized treatment plan.
How Do I Know If I Have SIBO or SIFO?
At Boulder Holistic Functional Medicine, identifying SIBO and SIFO starts with symptom assessment and a thorough medical history. Given that their symptoms overlap with other gastrointestinal disorders, accurate diagnosis is key to effective treatment.
How to Test For SIBO
Small intestine bacterial overgrowth is more widely recognized in the medical world which makes it a bit easier to diagnose. Here are two tests to diagnose SIBO.
Breath Tests: Non-invasive and widely used, these tests measure hydrogen, methane, and sulfur levels in the breath after consuming a sugar solution. Elevated levels indicate bacterial overgrowth in the small intestine.
Organic Acids Testing: These tests use urine to measure bacterial and fungal metabolites. Elevated levels can help guide diagnosis of bacterial or fungal overgrowth.
How to Test For SIFO
SIFO is relatively lesser-known and therefore more difficult to diagnose. It often involves ruling out other causes of symptoms and a careful evaluation of patient history, especially when it comes to antibiotic use, environmental exposures and immune status. For now, the organic acid test is the best tool we have for people with SIFO.
Diagnosing SIBO and SIFO is just the first step. Once identified, a functional medicine approach can effectively address these complex conditions.
Functional Medicine Approach to Treating SIBO and SIFO
Boulder Holistic Functional Medicine uses a holistic approach to treat SIBO and SIFO. We go beyond symptom relief to identify and address the root causes of these conditions so we can find you a more comprehensive and long-lasting solution.
Over the years, Boulder Holistic Functional Medicine has successfully treated SIBO and SIFO using a variety of approaches. A brief summary of each is included below. We have also included our supplement recommendations for anyone who is in the process of healing from SIBO and SIFO.
Boulder Holistic Treatment Approaches for SIBO and SIFO:
- Address Structural Issues: Treatment for SIBO may involve addressing an underlying structural problem, like surgically repairing a postoperative loop, stricture, or fistula. Visceral manipulation may also help with less serious structural issues.
- Address Motility Issues: Food poisoning or stomach bugs can damage the migrating motor complex in the small intestines which can cause stagnation in the small bowel and contributing to the development of SIBO and SIFO. At Boulder Holistic Functional Medicine, we use pharmaceutical or advanced nutraceuticals to restore proper motility in the gut.
- Targeted Antibiotic Therapy: Antibiotics are a common first step when treating SIBO. While antibiotics are a cornerstone in SIBO treatment, functional medicine often advocates for a judicious use of these medications, considering their impact on gut microbiota. Long-term treatment options may be necessary because bacteria may return after your antibiotics are complete. Xifaxan is the treatment of choice as it has a less detrimental effect on the good bacteria and only targets the bad bugs.
- Nutritional Support: Correcting nutritional deficiencies is crucial for anyone with SIBO or SIFO. This may include intramuscular injections of vitamin B-12, oral vitamins, and iron supplements.
- Dietary Changes: Limiting sugar and refined carbs can help curb SIFO symptoms as Candida cells flourish in the presence of glucose.
- Movement and Meal Spacing: Frequent movement and spacing out meals by 3-5 hours can improve gastrointestinal motility, which is essential to prevent SIFO. You may also want to consider eating at least 3 hours before going to bed.
- Address Low Stomach Acid: Supplements like hydrochloric acid (HCL) may be recommended if low stomach acid is diagnosed, to aid in digestion and inhibit fungi and bacteria.
- Antifungal Treatment: Antifungals play a crucial role in managing SIFO, but like antibiotics, functional medicine recommends you limit their use when possible because of how they affect the gut microbiota.
If you think you have SIBO or SIFO, we highly suggest you work with a functional medicine practitioner or PCP to properly diagnose and treat these issues!
Boulder Holistic Supplements For SIBO and SIFO:
Functional medicine’s holistic approach to treating SIBO and SIFO involves more than just medication; it includes a range of targeted supplements to address specific types of overgrowth.
For Bacterial Overgrowth (SIBO):
Supplements like berberine and aromatic oils such as oregano oil are often utilized for their antimicrobial properties. Biocidin is also a great choice for the treatment of SIBO in some people.
For Fungal Overgrowth (SIFO):
In addition to the treatments for SIBO, supplements like garlic, bee propolis and undecylenic acid are used for their antifungal effectiveness.
For Sulfur-Producing Bacteria (SISO):
Supplements containing mastic gum and bismuth are added to specifically target these types of bacteria. These supplements, combined with dietary modifications and lifestyle changes, are a powerful addition to any treatment plan as long as they are tailored to the individual’s specific needs and the type of overgrowth present.
What Should I Eat If I Have SIBO and SIFO?
Finding a diet to support your gut while you recover from SIBO or SIFO can feel impossible. But what you eat during treatment is an essential consideration.
All of the diets listed below are considered antimicrobial strategies for both SIBO and SIFO. Not only do these diets provide guidance for patients who need to avoid the foods that feed bad bacteria and funguses, they also replace nutrition and restore healthy gut microbiota.
These diets can be used alone, or as a part of a greater SIBO/SIFO treatment protocol.
- Low FODMAP Diet: This diet reduces the intake of certain carbohydrates that are poorly absorbed by the gut, which can help alleviate SIBO symptoms.
- Specific Carbohydrate Diet (SCD): This diet focuses on eliminating complex carbohydrates that are difficult to digest, thereby reducing bacterial overgrowth.
- Biphasic Diet: A structured approach that starts with strict dietary restrictions followed by a gradual reintroduction of foods, tailored to manage SIBO.
- Elemental Diet: Often used as a short-term intervention, this diet consists of easily digestible formulas that provide nutrients in their simplest form, reducing the work required by the gut.

Each diet is considered an intervention and should be used only for as long as it is needed to control symptoms. After that, you should expect to reintroduce healthy foods one at a time so you aren’t locked into a super restricted diet long-term.
Lifestyle and Supplemental Support
Functional medicine also emphasizes the importance of lifestyle changes and the use of supplements to restore gut health. This includes stress management, regular exercise, and the use of probiotics, prebiotics, and digestive enzymes.
With SIBO and SIFO, the timing of replacing pre and probiotics is important. If introduced too soon in treatment, it can make your digestive symptoms worse.
By incorporating these treatment strategies, functional medicine offers a path to not just managing but potentially resolving the complexities of SIBO and SIFO.
Work with Boulder Holistic
Boulder Holistic Functional Medicine understands how challenging it can be to navigate the complexities of Small Intestinal Bacterial Overgrowth (SIBO) and Small Intestinal Fungal Overgrowth (SIFO). However, we also know that with the right approach, you can effectively manage and treat any gut dysfunction.
Functional medicine offers a comprehensive strategy that not only targets the symptoms but also addresses the underlying causes of these conditions. Through a combination of targeted antibiotic and antifungal therapies, targeted herbal therapies, personalized dietary plans like the Low FODMAP, Specific Carbohydrate, Biphasic, and Elemental diets, and lifestyle modifications, patients can find relief and a path to improved gut health.
Moreover, advanced diagnostic tools like the breath-based Tri-Test, NutrEval, and Organic Acid Tests provide deeper insights into gut health, guiding more precise treatments.
Remember, everyone’s journey with SIBO and SIFO is unique. Contact Boulder Holistic Functional Medicine in Boulder, Colorado, for your customized SIBO and SIFO treatment and heal your gut naturally.

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