SIFO, or small intestinal fungal overgrowth, occurs when an excess amount of fungi or yeast grow in the small intestine of the digestive tract. This overgrowth may be associated with gastrointestinal symptoms such as abdominal bloating and pain, gas, belching, diarrhea, and nausea, and over time may contribute to malnutrition and weight loss if not addressed.
SIFO is a potential factor in gastrointestinal distress, found in around 25% of people with previously unexplained gastrointestinal symptoms, such as those that occur with irritable bowel syndrome (IBS). The majority of SIFO cases involve an overgrowth of Candida species, which are normal in small amounts in the mouth, skin, and intestines, but may contribute to issues when they multiply excessively.
Fortunately, a functional medicine approach can help to explore some contributing factors that may allow these yeasts/fungi to proliferate. Lifestyle and dietary interventions may help to support the balance of microbes in the gut and manage symptoms of SIFO in many cases.
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What is Small Intestinal Fungal Overgrowth (SIFO)?
Fungal strains (like bacterial strains) are a normal part of the gut ecosystem as part of a diverse microbiome. Bacteria and fungi mostly colonize the large intestine, with far fewer microbes in the small intestine. When heavier colonization and/or an imbalance of microbes occur in the small intestine, an overgrowth can occur that may lead to gastrointestinal distress.
When fungal species colonize and overgrow in the small intestine, SIFO may occur. Research suggests that 97% of the fungi associated with SIFO is a form of Candida, such as Candida albicans. Candida species are yeasts or fungi that normally live on your skin and inside your mouth, throat, gut, and vagina. When in balance, Candida yeasts may help maintain a healthy balance of microorganisms in these different areas, as well as supporting your immune system, aiding in digestion, and promoting vitamin and mineral absorption from food.
However, if fungi like Candida overgrow in the small intestine, it may disrupt the balance of microbes and contribute to problems like SIFO.
SIFO Symptoms
SIFO may cause a variety of common digestive symptoms, many of which are similar to those that occur when bacteria overgrow in the small intestine (SIBO) and with IBS. Studies suggest that SIFO may be a common factor in gastrointestinal distress, found in around 25% of people with previously unexplained gastrointestinal symptoms, such as those that occur with IBS.
The most commonly reported symptoms of SIFO include:
- belching
- bloating
- gas
- indigestion
- fullness in the upper abdomen
- nausea
- diarrhea
Fungal overgrowth in the small intestine may have impacts that go beyond the gastrointestinal tract. Fungal overgrowth can occur in other sites of the body as well, resulting in additional signs such as:
- chronic skin yeast infections or rashes in areas where skin meets skin, like armpits or under the breasts
- vaginal yeast infections
- itching behind the ears
- toenail fungus
- thrush (a white coating on the tongue)
- urinary tract infections
If not addressed, SIFO may contribute to inflammation throughout the body as well as malnutrition and weight loss.
What Causes SIFO?
Several factors can make it more likely that fungi will overgrow in the small intestine or other body sites. To maintain a healthy balance of gut bacteria and fungi, you need proper immune function, stomach acid, and bowel motility.
Immunocompromise
Overgrowth of fungi is more common in people with weakened immune systems, including:
- very young children
- the elderly
- people taking immunosuppressant drugs like steroids after an organ transplant or for certain autoimmune diseases
- people with disorders that involve immunocompromise, like HIV/AIDS and diabetes
Low Stomach Acid
Low stomach acid may increase the risk of fungal overgrowth since stomach acid plays a key role in managing bacteria and fungi before they enter the small intestine. Low stomach acid can occur from:
- long-term use of proton-pump inhibitor (PPI) medications
- age over 65 years
- nutrient deficiencies, including protein, iron, calcium, and vitamin B12
- infection with H.pylori
- atrophic gastritis
Antibiotic use
Antibiotics can reduce healthy bacteria and other microbes in the gut, making it more likely that fungi (or certain bacteria) can overgrow and contribute to SIFO.
Slow Motility
When the movement of food through the small intestine is slowed, it may increase the risk of bacteria and fungi overgrowth. Some causes of slowed gastrointestinal motility include:
- diabetes
- Ehlers-Danlos syndrome
- colectomy surgery that removes part of the intestines
- sedentary behavior, which may impair blood flow to the digestive tract
- gastroparesis
- thyroid disorders, including hypothyroidism and Hashimoto's
Lifestyle Factors
Additionally, some lifestyle factors may contribute to dysbiosis and SIFO.
- eating a diet high in refined carbs or sugars
- excessive alcohol consumption
- chronic stress
Testing for The Root Cause of SIFO
Comprehensive Stool Testing
A comprehensive stool test like the GI Effects reflects the overall health and balance of the digestive tract by measuring a variety of microbes and intestinal health markers. This test may help identify Candida albicans overgrowth and explore possible reasons for the overgrowth, such as dysbiosis. Retesting a few months after dietary changes or other interventions can guide an individualized approach.
SIBO Breath Test
Since SIBO and SIFO can present with very similar symptoms and often occur together, it is essential to evaluate for an overgrowth of bacteria in the small intestine when SIFO is suspected. A breath test can evaluate the overgrowth of bacteria that do not normally belong in the small intestine. The 3-hour SIBO assessment is a non-invasive breath test that measures hydrogen and methane to evaluate bacterial overgrowth in the small intestine.
Small Bowel Aspirate Test
The "gold standard" for identifying SIFO is a small bowel aspirate. This procedure involves inserting a tubular instrument through the esophagus and stomach into a portion of the small intestines called the duodenum during an upper endoscopy. From there, fluid is collected and analyzed for the presence of fungi and/or bacteria.
Integrative Medicine Approaches for SIFO
Dietary approaches to dysbiosis, like SIFO, should be individualized. The Anti-Candida, Low FODMAP, anti-inflammatory Mediterranean diet, and elemental diets may be considered in some cases.
Anti-Candida Diet
The Anti-Candida Diet includes non-starchy vegetables, some low-sugar fruits, non-gluten grains, some dairy products, and fermented foods. This low-sugar, anti-inflammatory diet is designed to help support the balance of yeast and bring the microbiome back into balance.
Low FODMAP Diet
A low FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) diet limits short-chain carbohydrates, which can be difficult to digest and may feed yeast and bacteria in the small intestine. Eliminating foods like beans and legumes, corn, seeds and nuts, and cruciferous vegetables that can irritate the stomach or cause delayed emptying may help manage symptoms for some. Following a gluten-free or grain-free diet may also support symptom management.
Rebalance the Gut Microbiome
A Mediterranean diet, emphasizing citrus fruits, vegetables, legumes, and complex carbohydrates with moderate fish and olive oil, may help balance inflammation and promote gut health. Restoring equilibrium in the gut microbiota by eating a variety of real whole foods and incorporating probiotic-rich foods like kimchi and sauerkraut that contain naturally-occurring probiotics and prebiotic-rich foods like artichokes, garlic, and beans that nourish healthy bacteria is critical for helping to bring the microbiome back into balance.
Elemental Diets
An elemental diet is a liquid meal replacement formula that provides a complete nutritional profile broken down into its most "elemental" forms. Proteins, fats, and carbohydrates are broken down into amino acids, short-chain triglycerides, and short-chain maltodextrins, along with vitamins, minerals, and electrolytes in a comprehensive "predigested" formula that is easily absorbed by the digestive tract. Fiber is generally excluded as it can feed bacteria that have relocated into the small intestines. An elemental diet may be used to support the management of SIBO or SIFO by replacing other food for a period of two to three weeks in an attempt to manage the bacteria in the small intestine while still adequately nourishing the body.
Herbal Medicine Approaches for SIFO
The standard approach for SIFO is several weeks of antifungal drugs such as fluconazole, itraconazole, or posaconazole which are active against candida.
Alternatively, probiotics and herbal antimicrobials like artemisinin, caprylic acid, oregano oil, garlic, and berberine are sometimes considered for antifungal support. While many of these approaches have been studied for SIBO and not SIFO directly, these herbal antimicrobials may offer both antibacterial and antifungal properties to help support the balance of the microbiome. The GI Effects comprehensive stool test can help guide a personalized approach by showing which prescriptive and natural agents may be effective at managing the growth of the candida specific to the patient's microbiome.
To help support a healthy balance of microbes when taking antibiotics, a probiotic containing the beneficial yeast, Saccharomyces boulardii may help support the prevention of SIFO.
Under medical guidance, replacing acid (betaine HCl or apple cider vinegar) and enzymes such as papain or bromelain extracts and stimulating digestion with bitters may help support stomach acid, motility, and digestion.
- Ginger is a natural prokinetic that may help support stomach emptying to relieve nausea.
- Other herbal prokinetic combinations such as bitter candytuft, angelica root, chamomile, and caraway, commonly found in the herbal formula Iberogast, have also been used to support dysmotility by helping the stomach muscles function appropriately.
Summary
An imbalance of microbes in the intestinal tract (dysbiosis) is increasingly being recognized as a potential factor in gastrointestinal and systemic symptoms. Small intestinal fungal overgrowth (SIFO) occurs when this imbalance involves too many fungi growing in the small intestine.
The most common type of yeast/fungal overgrowth that may contribute to SIFO involves Candida. This proliferation of fungi in the small intestine may be associated with gas, bloating, nausea, and diarrhea, along with malnutrition and weight loss if left unaddressed.
Intestinal dysmotility, low stomach acid, immunocompromise, long-term treatment with PPIs, and gastrointestinal dysbiosis can all increase the risk of developing SIFO. While a small bowel aspirate to collect a sample of fluid from the small intestine is the gold standard for identifying SIFO, functional medicine testing to look at microbes in the gastrointestinal tract and rule out SIBO can help with narrowing in on factors contributing to SIFO.
A diet focused on non-starchy vegetables, some low-sugar fruits, non-gluten grains, and fermented foods may help support the balance of yeast and bring the microbiome back into balance. Prescription or herbal antifungals are sometimes used to help manage the growth of fungi in the small intestine. Probiotics and natural approaches to supporting stomach acid and motility may also help manage symptoms and support the prevention of SIFO.
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