Functional Medicine for SIBO, SIFO and IMO

What are SIBO, SIFO and IMO?

Your small intestine normally has far fewer bacteria than your large intestine (colon). Small intestinal bacterial overgrowth (SIBO) is when too many bacteria grow in the small intestine and cause digestive symptoms. These bacteria are usually types that are typically found in the colon.^{1, 2, 4}

The extra bacteria can break down food that your body would normally absorb, which can make extra gas and cause bloating. They may also use up nutrients your body needs. As a result, some people become malnourished (not getting enough nutrients).^{1, 2}

Intestinal methanogen overgrowth (IMO) is a newer term for too many methanogens, which are microbes that make methane gas. They are not bacteria but belong to a different group called archaea, and they can overgrow in the large intestine, not just the small intestine. A positive methane breath test is linked with constipation.¹

Small intestinal fungal overgrowth (SIFO) means too many fungi, mostly a type called Candida, in the small intestine, along with digestive symptoms. Research on SIFO is still early, and experts say more studies are needed to confirm it and to learn how much it matters. What leads to SIFO is unclear, but slow movement of the small intestine and the use of proton pump inhibitors (PPIs) have been linked to it. PPIs are among the most common medicines for digestive symptoms.^{1, 3, 5}

SIBO almost always happens because of something else, usually a problem that lets food and fluid sit too long in the small intestine. Things linked with SIBO include:¹

• Diseases that slow the movement of the small intestine, such as diabetes^{1, 2}
• Some surgeries on the stomach or bowel^{1, 2}
• Crohn's disease, which can cause pouches or blockages in the small intestine^{1, 2}
• Medicines that slow the gut, such as opioids¹
• Use of PPIs, although the link is complex¹
• A weak immune system^{1, 2}
• Older age¹
• Some cases of irritable bowel syndrome (IBS)^{1, 2}

Common symptoms of SIBO, SIFO and IMO

No single symptom points to SIBO. Its symptoms often look like other conditions, such as IBS, and people with and without overgrowth report similar symptoms. That is why testing is needed to diagnose it.^{1, 4, 6}

Common symptoms include:^{1, 2, 3}

• Bloating, gas and a feeling of fullness^{1, 2}
• Belly pain or cramping^{1, 2}
• Diarrhea, most often watery^{1, 2}
• Constipation, which is linked with methane (IMO)¹
• Nausea^{1, 3}
• Belching and indigestion, which are common in SIFO³
• Tiredness and trouble concentrating, in some people¹
• In severe cases, weight loss, fatty stools, or low levels of vitamin B12, vitamin D or iron^{1, 2}

How SIBO, SIFO and IMO are diagnosed and treated

A breath test is often the first test used. You drink a sugar solution, usually glucose or lactulose, and then give breath samples over time. Human cells cannot make hydrogen or methane gas, so these gases in your breath come from microbes in your gut breaking down the sugar. A rise in hydrogen suggests SIBO, and a high methane level suggests IMO.^{1, 4}

Breath tests are easy, fairly low-cost and widely available, but they have real limits. They measure bacteria only indirectly, and current tests have low accuracy and need more study. The lactulose test has been criticized for false positive results (showing SIBO when it is not there), and the glucose test can miss overgrowth lower in the small intestine. Home test kits are available, but the diet steps and breath collection at home may not be strictly controlled.^{1, 4}

Another test takes a small sample of fluid from the small intestine during an upper endoscopy, when a doctor passes a scope through the mouth and stomach. The sample is grown in a lab. This is often considered the gold standard (the best test available). But it is a scope procedure that needs sedation, it is expensive, and there is no standard way to do it. In one study, the two kinds of tests agreed only about 65% of the time.^{1, 4}

There is no standard test for SIFO. Breath tests are not a reliable way to find fungal overgrowth. The best available method is a fluid sample from the small intestine, taken during an endoscopy and grown in a lab for fungi. But this method needs a scope procedure and is not widely available. SIFO is still debated, and there are no agreed guidelines for diagnosing it.^{4, 5}

When possible, doctors treat the cause of the overgrowth. Antibiotics are the main treatment for SIBO, but the evidence comes mostly from small studies of poor to modest quality. Guidelines advise confirming SIBO with testing before using antibiotics, and SIBO often comes back after treatment.^{1, 2}

For SIFO, antifungal medicine is sometimes used, but it is not yet clear whether clearing the fungi relieves symptoms. Diets that cut back on foods gut microbes ferment, such as a low FODMAP diet, are also used, but most of that evidence comes from IBS research. Studies of probiotics for SIBO have mostly been small and of poor quality.^{1, 3}

Overall, the American College of Gastroenterology says most of its SIBO recommendations have low levels of evidence to support them, and better tests and treatments are needed.¹

How our care fits alongside your gastroenterologist

Avicenna Functional Medicine does not replace your gastroenterologist or the treatment they prescribe. Our role is to add to your care, not to take its place.

In a functional medicine visit, we look at factors that may contribute, such as how food moves through your gut, past surgery, medicines, other health conditions and diet, alongside the care you already receive. Research has linked slow gut movement, some surgeries, some medicines and some health conditions to SIBO, but much of that research is still limited. What you eat can also change how much gas gut microbes make.^{1, 2}

Any testing we suggest is chosen for you. A breath test is only one part of the picture, because SIBO symptoms overlap with IBS and other conditions that your doctor may need to rule out. Breath tests also cannot reliably detect fungal overgrowth. If testing points to an overgrowth, your clinician uses the results, along with your symptoms and history, to shape a personalized plan, with follow-up visits to check your progress.^{1, 5, 6}

Please do not stop or change any prescribed medication without talking to the doctor who prescribed it. This includes medicines such as PPIs, even though they have been linked to SIBO.¹

What to expect at Avicenna

All visits are by telehealth, for patients located in Florida and Texas. We are a cash-pay practice, and we accept HSA and FSA. Care usually follows these steps:

• A free, 30-minute discovery call to talk about your health and whether our approach is a good fit for you
• A full intake visit with our health coach, under clinician supervision, covering your history, symptoms, current treatment and goals
• Testing chosen for you, where it is likely to be useful
• A personalized plan, with follow-up visits to review how you are doing and adjust the plan as needed

When to get urgent care

Contact your doctor if you notice changes in your bowel habits that do not go away. SIBO has symptoms similar to those of IBS. But blood in the stool and weight loss you didn't intend are not part of IBS. If you have them, work with your doctor to find out why. In severe cases, SIBO can lead to malnutrition and dehydration.^{2, 6}

Telehealth visits with our team are not for emergencies. Call 911 right away if you have warning signs of a medical emergency, such as:⁷

• Chest pain or pressure that lasts two minutes or more⁷
• Trouble breathing or shortness of breath⁷
• Sudden confusion, unusual behavior or trouble waking up⁷
• Fainting or passing out⁷
• Sudden dizziness, weakness or changes in vision⁷
• Being unable to speak⁷
• Severe belly pain, or sudden severe pain anywhere in the body⁷
• Coughing up or vomiting blood⁷
• Thoughts of suicide or of harming someone else (you can also call or text 988)^{7, 8}