SIFO is an acronym that stands for small intestinal fungal overgrowth. It happens when there’s an excess amount of fungi in your small intestine.

You may be wondering how SIFO could potentially affect your gut health. In this article, we’ll take a closer look at what exactly SIFO is, its symptoms, risk factors, and how it may be treated.

SIFO is a condition in which high levels of fungi are found in the small intestine. This overgrowth may often cause gastrointestinal (GI) symptoms.

While GI fungal overgrowth can often develop in individuals with a weakened immune system, it can also occur in people with healthy immune systems. In fact, two studies found that about 25 percent of people with unexplained GI symptoms had SIFO.

In one of these studies, over 97 percent of the fungi were found to be the Candida species.

Candida is normally found in small amounts in your mouth, on your skin, and in your intestines. At low levels, it doesn’t cause any problems.

But, if it isn’t kept in check and grows uncontrollably, it can cause a variety of common infections, such as vaginal yeast infections and oral thrush. And it can also upset your gut health if there’s an overgrowth in your intestines.

The symptoms of SIFO are very similar to other conditions that cause chronic or recurring GI symptoms. Some of the most common symptoms include:

SIFO may also cause more severe symptoms. For example, one case study found that SIFO was associated with malnutrition and weight loss.

Overgrowth of fungi, particularly Candida species, is often more prevalent in specific groups of individuals, such as:

  • older adults
  • young children
  • people with a weakened immune system

However, people with a healthy immune system can also develop SIFO. How or why this occurs is poorly understood, but some possible risk factors have been identified:

  • Intestinal dysmotility. This happens when contractions of the intestinal smooth muscle are impaired. It can be inherited or caused by other health conditions like diabetes, lupus, or scleroderma.
  • Proton pump inhibitors (PPIs). These medications work to lower the levels of acid in your stomach. PPIs are often given to relieve the symptoms of gastroesophageal reflux disease (GERD).

SIFO can also occur along with small intestinal bacterial overgrowth (SIBO). The two conditions share similar symptoms. Like SIFO, many aspects of SIBO are still poorly understood.

The potential effects that SIFO may have on gut health are still unclear. Further research is needed to determine if people with fungal overgrowth in their small intestines are at risk for other health issues.

It’s worth noting that, according to research from 2011, colonization of the GI tract with Candida species has been associated with the following health issues:

Intestinal fungi also may play a role in irritable bowel syndrome (IBS). However, additional research into this topic is needed as well.

Currently, the only way to definitively diagnose SIFO is to collect a sample of fluid from your small intestine. This is known as a small bowel aspirate.

In order to collect the sample, an instrument, called an endoscope, is passed through your esophagus and stomach and into your small intestine. A sample of fluid is collected and then sent to a laboratory for testing.

At the laboratory, the sample is tested for the presence of fungi. If fungal growth is found in the sample, the species of fungus as well as its sensitivity to antifungal drugs can be determined.

Because SIFO isn’t well understood, the most effective treatment methods have yet to be determined.

If high amounts of fungi are identified from your fluid sample, you may be prescribed a course of an antifungal drug. An example of one such drug that you may be given is fluconazole.

However, antifungal drugs may not completely eliminate GI symptoms. One small study found that individuals who were prescribed antifungal drugs for SIFO reported limited improvement.

Studies into how diet can affect SIFO are very limited. Many studies into fungi and diet don’t specifically focus on the small intestine.

You may have heard that the Candida diet may help with Candida overgrowth, which is the type of fungus often found in the small intestine of people with SIFO. The diet focuses on avoiding:

  • grains that contain gluten, such as wheat, rye, barley, and spelt
  • high-sugar fruits, like bananas, mangos, and grapes
  • sugar, sugar substitutes, and sugary beverages
  • some dairy products, like cheese, milk, and cream
  • refined oils, like canola oil, soybean oil, and margarine
  • deli meats
  • caffeine and alcohol

However, at this point in time, there isn’t much clinical evidence of the effectiveness of this diet for reducing SIFO symptoms.

There are some more general studies that have been performed on diet and GI fungi. For example:

  • According to a 2017 study, the types of fungi that colonize your GI tract can vary depending on if you’re vegetarian or if you consume a more conventional diet.
  • A 2013 study found that Candida colonization was more prevalent in individuals who consumed a lot of carbohydrates, and less likely among individuals whose diets were high in amino acids, protein, and fatty acids.
  • According to a 2019 study, individuals with GI samples that were negative for Candida consumed less refined wheat flour products (like white bread and white pasta) and more healthy wheat flour substitutes, yellow cheese, and quark (a mild creamy dairy product similar to cottage cheese or yogurt).

If, and how, these findings relate to SIFO is yet to be determined by research.

SIFO is a condition that happens when there’s an excess amount of fungi present in your small intestine. It can cause various GI symptoms, such as bloating, abdominal pain, and diarrhea.

Many aspects of SIFO, such as what causes it and its effect on your gut health, are still poorly understood. Research is still ongoing in these areas.

Although SIFO may be treated with antifungal drugs, GI symptoms may not be completely alleviated. If you’re having unexplained GI symptoms that are recurring or chronic, be sure to visit your doctor to get a diagnosis.