What is SIBO? A Guide to This Under-The-Radar Gut Health Condition

Bloating, flatulence, abdominal pain? It could be small intestinal bacterial overgrowth (SIBO), an increasingly common condition caused by too much bacteria in the wrong part of your GI tract. If you have persistent gastrointestinal symptoms or IBS, you’ll want to read on for the full intel on SIBO, which could be the underlying cause of your symptoms.

What is SIBO?

SIBO stands for small intestinal bacterial overgrowth, a condition that can cause chronic digestive issues and symptoms like the ones mentioned above. But what is SIBO, really? “The way I think about SIBO is an overgrowth of bugs—and not just any bugs, but the wrong kind of bugs—high up in the intestines where they’re not supposed to be,” says Dr. Lilli Link, M.D ., a board-certified internist and functional medicine practitioner at Parsley Health in New York City.

In the medical literature , SIBO is often defined as more than 100,000 colony-forming units of bacteria per mL of proximal jejunal fluid, which just means a high concentration of bacteria in one specific section of the small intestines. These bugs produce gases, like methane and hydrogen, that contribute to the uncomfortable SIBO symptoms.

What are common SIBO symptoms—and how common is it?

Whenever a patient says something along the lines of, “My stomach is flat in the morning but by nighttime, I feel and look like I’m six months pregnant,” Dr. Link immediately suspects SIBO. IBS-like symptoms are also very common. “That’s constipation, diarrhea, alternating constipation and diarrhea, reflux, GERD, a lot of burping and passing of gas , and bloating , especially after your meals,” she continues. According to a 2010 study published in the World Journal of Gastroenterology, malabsorption, weight loss, and malnutrition are three other symptoms to look out for.

The initial thinking was that SIBO was very rare; as a result, many patients went undiagnosed or were misdiagnosed. As Johns Hopkins researcher Hazel Veloso, M.D., explained in an ar t icle in ACP Internist, “We were just labeling patients [without classic risk factors] with IBS before, and they were not better because there was actually an underlying cause.” When Dr. Link went to medical school 25 years ago, she never heard the term SIBO. “Maybe in the past 10 years, doctors have started to test for it and it’s become something we hear about more,” she says.

The truth is, it’s not entirely clear how common SIBO is in the general population. What we do know, though, is that a lot of people with IBS likely have it. In fact, a 2018 study showed that the odds of a SIBO diagnosis in IBS were increased five-fold.

SIBO causes explained

“There is an evolving understanding of why we get SIBO,” says Dr. Link. That said, “Antibiotics are thought to be one reason; sometimes bad gastroenteritis seems to be a trigger; and anecdotally, stress can also be a big factor,” she continues.

According to Johns Hopkins Medicine, risk factors for SIBO include structural abnormalities (like those caused by gastric bypass surgery, diverticulitis , or scar tissue), certain medications (such as narcotics or antibiotics when they’re used regularly), chronic disease like diabetes or lupus, and a lowered immune system .

“It’s also suspected that people without enough stomach acid are at risk for SIBO,” says Dr. Link. The same is true for those with diabetes or celiac disease. Basically, “anything that affects the motility of your GI tract will increase your risk of developing SIBO,” she explains.

But can a poor diet cause SIBO? According to Dr. Link, diet can improve SIBO symptoms but she’s not aware of diet causing SIBO directly. That said, “Not all the facts are out there yet,” she says; so it is possible.

What’s involved in a SIBO test?

According to that same 2010 study , which is titled “Small intestinal bacterial overgrowth syndrome,” the gold standard for diagnosing SIBO is a microbial investigation of the jejunal aspirates. This is done through an endoscopy, which takes a culture of the fluid and mucus in the small intestines. There are also non-invasive breath tests, which use glucose or lactulose to test for hydrogen and methane gases being produced by the gut bacteria.

At Parsley Health “We use the lactulose breath test that looks for hydrogen and methane gasses,” says Dr. Link. It’s pretty simple: you drink a liquid that has a specific kind of sugar designed to feed the bugs. Then, you measure the gases they produce with a SIBO breath test to get an idea of how many bugs are there and what kind.

What’s in a SIBO treatment plan?

SIBO is typically treated with a combination of herbal antimicrobials and pharmaceutical antibiotics. According to Dr. Link, “The general goal with the treatment for SIBO is to bring down the level of gasses being produced, which you do by killing off the bugs that are producing the gas in the first place.”

The type of SIBO treatment depends on the severity of the case. For someone with a significant case of SIBO—as determined by a lactulose breath test—Dr. Link would follow the following three-part plan:

1. Antibiotics

The first step is a two-week course of oral antibiotics, which would be selected based on the type of gases produced. As Dr. Link explains it: “For hydrogen gas-producing bugs we would use Rifaximin and if the results show methane gas, we would use a combination of Rifaximin and Neomycin.”

2. Herbal antimicrobials

The second step of SIBO treatment is herbal antimicrobial supplements . “For hydrogen gas, we use berberine and oregano oil. For methane gas, we use allicin,” says Dr. Lilli. If these ingredients are foreign to you, you’re not alone. Berberine is a chemical found in plants like goldenseal and turmeric that is known for its gut microbiota modulating properties and oil of oregano is a well-documented and well-studied ingredient that directly kills—or strongly inhibits—the growth of intestinal microbes. Allicin is one of the main compounds found in freshly crushed garlic and is known for its potent antimicrobial properties. “These supplements make up part two of the plan and we do them for about a month,” says Dr. Link.

3. Focus on motility

The final step of SIBO treatment lasts about three months and focuses on motility. “We use a combo of supplements; one called Motilpro and one called Atrantil ,” says Dr. Link. Both supplements are formulated to support gut motility and kill—or keep in check—the gas-producing bugs responsible for SIBO. Dr. Link also recommends a spore-based probiotic that’s designed to get past the stomach acid to target SIBO in the small intestines.

The three-step process above may seem simple, but treating SIBO isn’t always cut and dry. As the authors of one study correctly wrote, “Therapy for SIBO must be complex, addressing all causes, symptoms and complications, and fully individualised. It should include treatment of the underlying disease, nutritional support, and cyclical gastro-intestinal selective antibiotics.”

So, what about nutritional support? A specific diet, called the low-FODMAP diet , is commonly recommended for those with SIBO. The acronym FODMAP stands for fermentable oligo-, di-, mono-saccharides and polyols, which are all types of poorly absorbed carbohydrates that can cause excessive fluid and gas accumulation and exacerbate IBS and SIBO symptoms. These dietary changes can help manage symptoms and should absolutely be included in a high-quality holistic treatment plan, but they won’t remove the imbalance on their own.

Do you have to take prescription antibiotics?

According to Dr. Link, “If someone has mild SIBO, you could do just antibiotics or just do herbal antimicrobials.” In fact, “There’s some evidence that herbals work as well as antibiotics,” she says. A 2014 study published by Johns Hopkins University compared common herbal therapies, such as oil of oregano or allicin, against rifaximin and found that herbal therapy is at least as effective as Rifaximin.

Therefore, if you have a mild case of SIBO, it’s possible that you could skip some of the steps in the plan above, including prescription antibiotics. “Not everyone needs the full treatment plan,” Dr. Link explains. “The goal is to lower those gases in whatever way you can,” she continues.

Does SIBO come back?

The short answer is yes, SIBO can come back. But as Dr. Link explains, “While it often comes back, it’s usually less severe and needs less treatment.” When Dr. Link has a patient with recurring SIBO, she has them return to the herbals, probiotics , and low-FODMAP diet, which usually does the trick.

There are also cases of SIBO that are particularly stubborn. “This can be very frustrating for the patient and practitioner,” says Dr. Link. One factor that might be playing a role in recurring SIBO is stress. As Dr. Link explains, “If you don’t deal with your stress levels, you might not have success treating your SIBO.”

And while we can’t get rid of stress entirely, managing it is always an option. Dr. Link recommends journaling, drawing, and coloring to reduce stress as well as a technique called HeartMath , which uses biofeedback technology to help you train your body to balance the nervous system.