Post Author: Victoria Tyler
What is SIFO?
Small Intestinal Fungal Overgrowth (SIFO) occurs when excessive fungi, usually Candida, grow in the small intestine. While some fungi naturally live in our digestive system, overgrowth can lead to persistent digestive issues.
Unlike Small Intestinal Bacterial Overgrowth (SIBO), which involves bacterial overgrowth, SIFO involves excessive fungi, which can contribute to similar but distinct symptoms. Traditionally, fungal overgrowth was thought to affect only those with weakened immune systems or those taking antibiotics or steroids. However, research in Current Gastroenterology Reports (Choung et al., 2015) found that about 25% of people with unexplained digestive issues had SIFO.
SIFO Symptoms
SIFO shares symptoms with other gut disorders, making diagnosis challenging. Key symptoms include:
- Bloating – Swelling or tightness in the abdomen, often after meals.
- Excessive Gas – Flatulence or burping due to fungal fermentation.
- Nausea – Persistent nausea, sometimes worse after eating.
- Indigestion – Discomfort or difficulty digesting food.
- Diarrhea or Constipation – Alternating bowel habits.
- Fatigue – Chronic tiredness due to malabsorption of nutrients.
- Brain Fog – Difficulty concentrating or mental fatigue.
- White Coating on the Tongue – A sign of Candida overgrowth (oral thrush).
- Burning Sensation in the Gut – More common in fungal overgrowth compared to bacterial overgrowth.
- Worsening Symptoms with Sugary or High-Carb Foods – Fungi thrive on sugars.
- Skin Issues – Itchy rashes or eczema, often linked to Candida overgrowth.
- Cravings for Sugar and Carbs – Since fungi feed on sugars, cravings can become stronger when SIFO is present.
What Causes SIFO?
The exact causes of SIFO aren’t fully understood, but factors that slow digestion or suppress the immune system can encourage fungal overgrowth. Some common triggers include:
- Long-term Antibiotic Use – Kills beneficial bacteria that keep fungi in check.
- Proton Pump Inhibitors (PPIs) – Reduce stomach acid, creating an environment where fungi thrive.
- High-Sugar and Processed Diets – Fuel fungal growth, especially Candida.
- Low Stomach Acid (Hypochlorhydria) – Fungi survive longer in a less acidic gut.
- Slow Motility (Gastroparesis) – Allows fungi to persist in the small intestine.
- Weakened Immune System – Conditions like diabetes or chronic stress can contribute.
- Dysbiosis (Gut Microbiome Imbalance) – When beneficial bacteria are outnumbered by harmful microbes, fungal overgrowth can develop.
Who Is at Risk for SIFO?
Individuals at higher risk include:
- People with autoimmune diseases or chronic illnesses.
- Those who frequently take antibiotics, steroids, or immunosuppressants.
- Individuals with a history of gut issues like IBS, IBD, or acid reflux.
- Those consuming diets high in refined sugars and processed foods.
How SIFO Affects Digestion:
SIFO can impact digestion by altering the gut microbiome, impairing nutrient absorption, and triggering inflammation. Fungal overgrowth disrupts the delicate balance of microbes in the small intestine, leading to fermentation, gas buildup, and irritation of the gut lining. This can contribute to leaky gut syndrome, where the intestinal barrier weakens and allows toxins to enter the bloodstream, triggering immune reactions and systemic inflammation.
Can SIFO Cause Other Illnesses?
SIFO does not just cause digestive symptoms—it may also contribute to other health conditions. Since fungal overgrowth can lead to chronic inflammation and immune dysfunction, it has been linked to issues beyond the gut, including:
- Chronic Fatigue – Ongoing fungal infections can strain the immune system, leading to persistent fatigue and low energy levels.
- Skin Conditions – Conditions like eczema, psoriasis, and unexplained rashes may worsen due to fungal overgrowth and the body’s immune response.
- Brain Fog and Mood Disorders – Some people with SIFO report difficulty concentrating, memory problems, and even anxiety or depression, possibly due to the impact of gut health on brain function (the gut-brain connection).
- Recurrent Vaginal or Sinus Infections – A weakened immune system and fungal imbalance in the gut can contribute to recurring infections in other areas of the body.
- Joint Pain and Autoimmune Reactions – Systemic fungal infections have been associated with autoimmune conditions, triggering joint pain and inflammatory responses.
Addressing SIFO may improve not only digestive health but also these related symptoms, highlighting the importance of proper diagnosis and treatment.
How to Test for SIFO
Diagnosing SIFO can be challenging because its symptoms often overlap with those of other gastrointestinal conditions like SIBO, IBS, and Candida overgrowth in other parts of the body. However, there are specific tests that can help identify fungal overgrowth in the small intestine:
- Duodenal Aspirate Culture – The gold standard test, involving fluid sampling from the small intestine to detect fungal overgrowth. This test is performed during an upper endoscopy and provides the most accurate diagnosis.
- Stool Testing – Some comprehensive stool tests can detect Candida and other fungal imbalances. However, stool tests primarily analyze the large intestine and may not always reflect small intestinal fungal overgrowth.
- Urinary Organic Acids Test (OAT) – Measures fungal metabolites in urine, such as D-arabinitol, which can indicate systemic Candida overgrowth. While not a direct test for SIFO, it can provide clues about fungal issues in the body.
- Breath Testing – While breath tests are commonly used for diagnosing SIBO, they are not reliable for detecting SIFO. However, a negative SIBO breath test combined with persistent symptoms may raise suspicion of SIFO.
- Blood Testing for Candida Antibodies – Some practitioners test for Candida antibodies (IgG, IgA, IgM), which may indicate past or present fungal infections. However, this is not a direct SIFO test and should be used in conjunction with other methods.
- Symptom-Based Diagnosis and Response to Antifungal Treatment – When testing is unavailable or inconclusive, a trial of antifungal medication may be used as a diagnostic tool. If symptoms improve with antifungal treatment, it may suggest the presence of fungal overgrowth.
What is the best diet for SIFO?
The best diet for SIFO focuses on reducing fungal overgrowth by eliminating foods that feed yeast and promoting gut healing. Here are the key principles:
1. Eliminate Sugars and Refined Carbohydrates
- Sugar feeds Candida and other fungi, so it’s important to avoid added sugars, honey, maple syrup, high-sugar fruits, and processed foods.
- Refined carbohydrates like white bread, pasta, and pastries can quickly turn into sugar in the body and should be limited.
2. Avoid Yeast-Containing Foods
- Fermented foods like bread, beer, wine, and certain cheeses contain yeast and may contribute to fungal overgrowth.
- Some people with SIFO may also react to kombucha, vinegar, and mushrooms.
3. Focus on Protein and Healthy Fats
- High-quality protein sources such as grass-fed meat, wild-caught fish, pastured eggs, and plant-based proteins help maintain energy without feeding fungi.
- Healthy fats like avocado, olive oil, coconut oil, and nuts (except for mold-prone ones like peanuts) support gut health.
4. Eat Non-Starchy Vegetables
- Leafy greens, cruciferous vegetables (broccoli, cauliflower, Brussels sprouts), zucchini, cucumbers, and bell peppers provide fiber and nutrients without feeding yeast.
- Limit high-starch vegetables like potatoes, corn, and winter squash.
5. Include Antifungal Foods
- Garlic, onion, oregano, ginger, coconut oil, and turmeric have natural antifungal properties and can help fight fungal overgrowth.
6. Support Gut Healing
- Bone broth, collagen, and fermented foods (if tolerated) help restore the gut lining.
- Probiotic-rich foods like sauerkraut and kimchi can support a balanced microbiome, but some people with SIFO may need to introduce them slowly.
7. Stay Hydrated
- Drinking plenty of water helps flush out toxins and supports digestion. Herbal teas like ginger, chamomile, and Pau d’Arco (which has antifungal properties) can also be beneficial.
What if I also have SIBO?
Increasingly we have seen a cohort of patients who have both small intestinal bacterial overgrowth and small intestinal fungal overgrowth.
SIFO symptoms versus SIBO
While Small Intestinal Bacterial Overgrowth (SIBO) and Small Intestinal Fungal Overgrowth (SIFO) share many overlapping symptoms, key differences can help differentiate between the two.
Shared Symptoms of SIBO and SIFO:
- Bloating and distension
- Gas (burping and flatulence)
- Abdominal pain or discomfort
- Nausea
- Diarrhea, constipation, or alternating bowel habits
- Food intolerances
- Fatigue
Symptoms More Common in SIBO:
- Foul-smelling gas or stools – Caused by excessive bacterial fermentation.
- Diarrhea-dominant (Hydrogen SIBO) or Constipation-dominant (Methane SIBO) – Depending on which gases the bacteria produce.
- Nutrient deficiencies – Particularly vitamin B12 deficiency due to bacterial competition.
- Weight loss – Malabsorption is more common in SIBO than SIFO.
Symptoms More Common in SIFO:
- Burning sensation in the gut – Fungal overgrowth can cause inflammation leading to burning or discomfort.
- More severe nausea – Often reported with SIFO compared to SIBO.
- White coating on the tongue (oral thrush) – A sign of Candida overgrowth, which may also be present in the gut.
- Worsening symptoms with high-sugar or high-carb foods – Fungi thrive on sugars, so SIFO symptoms may flare up with carbohydrate intake.
- Fatigue and brain fog – More pronounced in SIFO due to systemic fungal toxins.
- Itchy skin or rashes – Candida-related SIFO can sometimes contribute to skin issues like eczema or rashes.
Key Takeaways:
- SIBO tends to be more associated with bloating, gas, and bowel movement changes (diarrhea or constipation).
- SIFO is often linked to burning gut sensations, nausea, worsened symptoms with sugar, and systemic symptoms like fatigue or rashes.
- Because they can co-exist, some people experience a mix of symptoms from both conditions.
Summary of SIBO vs. SIFO
- Cause:
- SIBO: Bacterial overgrowth in the small intestine.
- SIFO: Fungal overgrowth (mainly Candida) in the small intestine.
- Symptoms:
- SIBO: Bloating, gas, diarrhea, constipation, and abdominal pain.
- SIFO: Similar symptoms to SIBO, but more burning sensation, nausea, and fatigue.
- Triggers:
- SIBO: Low stomach acid, slow gut motility, IBS, diabetes, and antibiotic use.
- SIFO: Long-term antibiotic use, proton pump inhibitors (PPIs), immune suppression, and a high-sugar diet.
- Diagnosis:
- SIBO: Breath test for hydrogen and methane gases.
- SIFO: Small intestine aspirate culture (requires endoscopy, difficult to access).
- Treatment:
- SIBO: Antibiotics (rifaximin, neomycin) combined with dietary changes.
- SIFO: Antifungals (fluconazole, nystatin) combined with dietary changes.
Case Study: Mary’s Journey to Recovery with SIBO and SIFO
Mary, a 38-year-old woman, had been struggling with persistent digestive issues for over two years. She was diagnosed with Small Intestinal Bacterial Overgrowth (SIBO) after experiencing bloating, nausea, diarrhea, and fatigue. Despite multiple rounds of antibiotics and dietary changes, her symptoms never fully resolved.
After further investigation, we suspected that Mary might also have SIFO. She had been taking proton pump inhibitors for years to manage acid reflux, which may have contributed to an overgrowth of fungi in her gut. Additionally, she had a long history of antibiotic use for acne in her younger years, which likely disrupted her gut microbiome. Mary also had a strong sweet tooth and frequently consumed sugary foods, which can feed fungal overgrowth.
We decided to test for fungal overgrowth using a stool test an an Oats TEST, and the results confirmed the presence of Candida. Once we shifted our focus on eradicating SIFO, Mary’s condition began to improve. We introduced a targeted antifungal protocol alongside dietary changes to reduce fungal overgrowth, including limiting sugar and refined carbohydrates. Within a few weeks, her bloating significantly decreased, and her energy levels improved. After completing her protocol, Mary was finally able to maintain a healthy gut, free from the symptoms that had impacted her daily life for so long. Her case highlights the importance of considering both bacterial and fungal overgrowth when dealing with chronic digestive issues.
If you have both SIBO and SIFO, your diet needs to address both bacterial and fungal overgrowth while still providing proper nutrition.
Here’s how to balance your approach:
1. Eliminate Foods That Feed Both Bacteria and Fungi
- Avoid sugar and refined carbs: These feed both bacteria (SIBO) and fungi (SIFO). Cut out processed foods, sweets, bread, and pasta.
- Limit high-FODMAP foods: These ferment in the gut and can worsen SIBO symptoms. Avoid onions, garlic, apples, and legumes initially.
- Reduce yeast-containing foods: Bread, beer, wine, and some cheeses can worsen SIFO.
2. Focus on Easily Digestible Proteins and Fats
- Lean meats, eggs, fish, and poultry provide necessary protein without feeding bacteria or fungi.
- Healthy fats like olive oil, coconut oil (which has antifungal properties), and avocado support gut healing.
3. Choose Non-Starchy Vegetables
- Leafy greens, courgettes, green beams cucumbers, bell peppers, and spinach are safe choices.
Herbal Treatments for SIFO and SIBO
When addressing SIFO (Small Intestinal Fungal Overgrowth) and SIBO (Small Intestinal Bacterial Overgrowth), herbal treatments can be an effective alternative or complement to pharmaceutical options. Many herbs have natural antifungal and antibacterial properties that help rebalance the gut microbiome without the harsh side effects of traditional medications.
Herbs for SIFO (Fungal Overgrowth)
These herbs are particularly effective in targeting fungal overgrowth
- Oregano Oil – Contains carvacrol and thymol, which have strong antifungal properties against Candida species.
- Garlic (Allicin) – A natural antifungal and antibacterial agent that helps inhibit fungal growth.
- Pau d’Arco – A South American herb that has been traditionally used to fight Candida and fungal infections.
- Berberine – Found in plants like goldenseal and barberry, berberine has antimicrobial properties that target both fungi and bacteria.
- Coconut Oil (Caprylic Acid) – A natural antifungal that disrupts fungal cell walls.
Herbs That Can Treat Both SIFO and SIBO
Since many patients experience both fungal and bacterial overgrowth, these herbs provide broad-spectrum antimicrobial benefits:
- Oregano Oil – Kills both bacteria and fungi.
- Berberine – Effective against bacterial and fungal overgrowth.
- Garlic (Allicin) – A natural antimicrobial agent that combats both bacterial and fungal infections.
- Black Walnut – Contains tannins that have antifungal and antibacterial properties.
By incorporating these herbs into a treatment protocol alongside dietary changes, probiotics, and gut-supportive nutrients, SIFO and SIBO symptoms can be effectively managed.
SIFO is a growing yet underdiagnosed condition that can significantly impact gut health and overall well-being. Its symptoms often mimic other digestive disorders, making proper testing crucial for accurate diagnosis. Addressing SIFO involves a combination of dietary changes, antifungal treatments, and gut-healing strategies.
For individuals experiencing persistent bloating, fatigue, and gut discomfort, working with a healthcare professional to identify and manage SIFO can lead to long-term relief and improved digestive health. Since SIFO frequently coexists with conditions like SIBO, adopting an integrated approach that considers both bacterial and fungal overgrowth is essential.
It is particularly important to consider SIFO in patients who do not fully respond to SIBO treatment. If symptoms persist after multiple rounds of SIBO-targeted therapies, fungal overgrowth may be a contributing factor. In such cases, incorporating antifungal strategies alongside bacterial treatments may be necessary for complete symptom resolution.
By incorporating an antifungal diet, natural or pharmaceutical treatments, and gut-friendly habits, individuals can successfully manage SIFO and restore their digestive health.
Why You Should Also See a Professional
References
- Choung et al., Current Gastroenterology Reports, 2015.
- Rao et al., Clinical and Translational Gastroenterology, 2016.
- Mukherjee, P.K., et al. Mechanisms of Fungal Pathogenesis in the Gut Microbiome, 2017.
- Zuo, T., et al. Gut Fungal Dysbiosis and Its Association with Inflammatory Bowel Disease, 2018.
Author – Victoria Tyler BSc Hons MBANT
Victoria Tyler owns and runs two busy clinics : Nutrition and Vitality and the IBS and Gut Disorder Clinic.
Nutrition and Vitality, along with the IBS and Gut Disorder Clinic, were founded with the goal of helping patients alleviate IBS symptoms by uncovering and addressing the root causes of their digestive issues.
As a Registered Nutritional Therapist, Victoria holds a BSc (Hons) in Nutritional Therapy and has trained with the Institute of Functional Medicine. She is also accredited by BANT and CNHC.
Before transitioning into health, Victoria earned a degree in Economics and an MBA, working with corporations including Canon and Vodafone. However, her own health challenges led her to pursue a career in Nutritional Therapy.
With a passion for learning, Victoria is committed to staying at the forefront of Functional Medicine. She helps patients manage IBS and other digestive disorders, including SIBO, Candida, and IBD, by identifying and addressing their root causes.
Victoria strongly believes that every symptom has an underlying cause, and there is always a solution to every health condition. To learn more, or to see patient reviews, visit Victoria’s profile on Google.
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