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Small Intestinal Fungal Overgrowth— Candida Growth in the Gut

The microbiome is a term that refers to non-human cells that colonize the gut. Bacteria and fungi, including Candida, are normal residents within the large intestine. With damage to the digestive system, however, the numbers and location of these microbes can become a health hazard. The first article to describe the phenomenon of fungal overgrowth in the small intestine was published in 2015.

An Explanation for Mystery Gut Symptoms

Published in Current Gastroenterology Reports, the article name this newly recognized condition small intestinal fungal overgrowth, or SIFO for short. The risk factors for this form of Candidiasis included people with weak immune system, steroid use, and antibiotic use. Most notably, the article recognized that the incidence might be as high as 25% in people who did not have immunocompromise with unexplained digestive symptoms.

The most common symptoms of SIFO are nonspecific. They include belching, bloating, indigestion, nausea, diarrhea, and gas. This condition may also feature visible signs. A white coat on the tongue may indicate oral thrush. Fungal issues of the skin include tinea skin patches and athlete’s foot. In women, chronic vaginal yeast infections can present with dryness, itching, and whitish discharge.

The reason for SIFO is impaired movement in the small intestine, a process known as small intestinal dysmotility. In the healthy digestive tract, there is a coordinated movement of the gut which propels food, microbes, and other matter forward from the small intestine to the large intestine. Immune-mediated injury can slow or even freeze this movement, allowing for microbes to colonize and grow within the small intestine, where they should not be.

There are objective tests that may indicate the presence of small intestinal overgrowth. An antibody test performed on the blood has low reliability because it is often negative even in the presence of this condition. But it can be helpful where it is positive. Another blood test measures beta-alanine, a metabolic byproduct of Candida that is sometimes elevated with SIFO. Low levels of secretory IgA in the blood or stool are another possible sign, as it may point to a weakened protective mucus barrier which serves as the guts front line defense against bacteria, food residues, parasites, and yeast.

Treatment Considerations

Antibiotics will not work for SIFO because antibiotics kill bacteria rather than fungi. In fact, prolonged antibiotic use is a risk factor for developing SIFO because it eliminates the bacterial competitors that co-populate the gut along with Candida. Antifungal therapy alone will not be effective—while medications such as Nystatin and Diflucan do eliminate Candida, they do not reverse the underlying intestinal dysmotility that caused the fungal overgrowth to materialize in the first place.

Recognizing the cause of the intestinal dysmotility is complex. In my practice, the most common cause is immune-mediated injury from respiratory exposure to water-damaged buildings. Breathing in the toxic stew results in numerous forms of immune dysregulation, most notably chronic inflammation, immune suppression, and autoimmunity. Food poisoning is another cause, which is perpetuated when the body forms self-attacking autoantibodies that can attack the structural proteins, such as vinculin, in the gut.

Diet and digestion quality is important for recovery. Processed food and processed sugars are literally food for Candida and will promote their growth. For individuals with low stomach acid, which is evolved to neutralize microbes, promoting acid production with supplements, such as betaine hydrochloric acid and digestive bitters. Stopping acid-neutralizing agents is important. Proton pump inhibitors and antacids weaken the protective acidity within the stomach. The optimal diet is high in protein and fat and may include a ketogenic and carnivore diet.

Select References

Erdogan A, Rao SS. Small intestinal fungal overgrowth. Curr Gastroenterol Rep. 2015 Apr;17(4):16. doi: 10.1007/s11894-015-0436-2. PMID: 25786900.

Banaszak, Michalina, et al. “Association between Gut Dysbiosis and the Occurrence of SIBO, LIBO, SIFO and IMO.” Microorganisms 11.3 (2023): 573.

Erdogan, Askin, et al. “Sa2026 small intestinal fungal overgrowth (SIFO): a cause of gastrointestinal symptoms.” Gastroenterology 146.5 (2014): S-358.