What Is SIBO? Symptoms, Treatments and More

If you have irritable bowel syndrome, acronyms are a big part of your life. There's the disease itself: IBS, with its hallmarks of bloating, altered stool patterns (constipation or diarrhea, or both) and chronic abdominal pain.

There's the diet you often end up eating to control these symptoms, low-FODMAP (FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols; these are sugars that the small intestine has a tough time absorbing).

And then there's the looming concern that, in addition to IBS, you could also be saddled with SIBO (aka small intestinal bacterial overgrowth). This condition can lead to nutritional deficiencies in addition to the abdominal pain and symptoms that afflict people with this condition. Indeed, some studies show that up to 80% of people with SIBO are IBS sufferers, so that fear is justified.

All of this alphabet soup aside, what is SIBO, exactly? And considering that the symptoms of small intestinal bacterial overgrowth are similar to a number of other gastrointestinal disorders (including IBS), how do you know if you have it?

As it turns out, there's a very simple, accurate breath test you can take at home which will give you the scoop on your SIBO status. We interviewed expert Dylan Blaiwes, who manages lab testing at Life Extension, to learn what this test measures, as well as what causes this disease—plus dietary measures to address SIBO (fortunately, they do exist!).

What is SIBO?

To put it in layman's terms, SIBO is an out-of-balance gut. Which is exactly as unpleasant as it sounds.

We all have trillions of bacteria within our microbiome; some of them are health-promoting and some are harmful. As Blaiwes explains it, when there's more bad bacteria than good, your gut feelings are going to be bad feelings. "SIBO refers to an overgrowth of unwanted gas-producing bacteria in the small intestine," he said. "This imbalance often leads to GI discomfort and other symptoms, typically shortly after eating a meal."

This is because the excess bacteria in your small intestine produce excessive gas when they digest the carbohydrates in your diet—and too much gas (due to bacterial overgrowth) can lead to all the symptoms Blaiwes mentions. Plus, it can even trigger diarrhea.

Not only that, but those bad bacteria in your small intestine can also gobble up healthy things from our diet rather than allowing our bodies to make proper use of them: we're talking about protein and vitamin B12 you won't be absorbing, as well as bile salts, which you need to digest fat.

Gas + undigested fats + not enough of the nutrients you need = one very uncomfortable you!

What causes SIBO?

You can end up with small intestinal bacterial overgrowth when stagnant food in your small intestine becomes a breeding ground for bacteria. So if waste is slow to leave your digestive tract (this condition, sometimes called slow motility, is common with some forms of irritable bowel syndrome and other gastrointestinal problems; "motility" refers to the movement of food through the digestive tract), you've got a big SIBO target on your back!

But there are a number of other causes of intestinal bacterial overgrowth:

• Gastric bypass surgery or other abdominal surgery—if there's a complication from these procedures, you can end up with an overgrowth of bacteria in your small intestine
• Crohn's disease
• Celiac disease
• Diabetes
• Diverticulosis
• Scar tissue in the small intestine or other structural problems with this part of your digestive tract

What are symptoms of SIBO?

Blaiwes said SIBO's most common symptoms include:

• Bloating
• Abdominal discomfort
• Bad breath
• Gas
• Diarrhea
• Constipation

Usually, these all hit within a few hours of eating a meal.

If small intestine bacterial overgrowth sounds a bit like IBS, that's not an accident. "Small intestinal overgrowth is also present in many IBS cases, so several IBS symptoms can also be related," Blaiwes explained. As is the case with IBS, fatigue can result.

Can you have SIBO and not know it?

Yes! In case you didn't notice, many of the symptoms above describe many different varieties of what most of us think of as a "tummy troubles." (Of course by "tummy," in this case, we're referring to the small intestine.) And since there's so much overlap between SIBO symptoms and IBS (and even to some extent Celiac disease and Crohn's symptoms), you could very easily be living with SIBO and have no idea.

"Many non-specific GI symptoms can also be tied to SIBO, so many people may not realize their after-meal "upset stomach" could be SIBO-related," Blaiwes said. "GI symptoms shortly after eating, especially bloating and gas, can point to a SIBO concern, and warrant testing."

This may be true even if your stomach issues don't seem all that frequent or debilitating, he added. "As SIBO relates to a combination of bacterial growth and dietary patterns, its severity and symptom frequency can vary," Blaiwes said.

The good news is that once you find out that you do have SIBO, if it's not terribly severe, you may be able to address this condition in simple, non-invasive ways: by modifying your diet and lifestyle. (More severe cases will require medical intervention.) Of course, if the test concludes it's not SIBO, you likely will want to do further testing to see what's causing your gastrointestinal distress. Your gastroenterologist may order X-rays and other diagnostic tools to pinpoint the cause.

So when in doubt, find out—with a simple breath test that you can do at home.

SIBO hydrogen breath test—how does it work?

That aforementioned "simple test" is called the SIBO Home Breath Kit and it measures two different gases in your breath, hydrogen and methane. When the bacteria in your small intestine consume sugars, they release these gases through a process called fermentation, and too much fermentation is an indicator of small intestinal bacterial overgrowth. The test is essentially ingesting a sugar solution at multiple intervals and then measuring how much fermentation occurs in your breath samples.

Specifically, here's how the test works:

• First, you get a baseline breath measurement (yep, you're just breathing—no blood draws or urine tests required!)
• Then, you consume a special sugar solution. Remember, sugar is what triggers the fermentation—aka, the release of different gases from your small intestine. You take a sample of your breath after you consume it to measure how much fermentation is occurring.
• You repeat this test every 20 minutes over a period of three hours.
• Typically, if excess fermentation occurs in the first 2 hours, this suggests an overgrowth of bacteria in the small intestine (SIBO).

Not only will this test let you know if you have small intestinal bacterial overgrowth, it will help pinpoint what part of the GI tract is experiencing the most severe bacterial overgrowth.

"By measuring the different mixture of gases in your breath, the test reveals how much bacterial fermentation is occurring, which helps determine the presence of bacteria in different parts of the GI tract," Blaiwes explained. This can include the small intestine as well as the large intestine, which also can host excess bacteria. "Depending on which type of gas rises (hydrogen or methane), this helps identify which bacterial species are present to guide the most effective interventions."

SIBO treatment options

You treat SIBO by eliminating the bacteria (the "B" in SIBO)—but how you go about doing that depends upon how severe your condition is, according to Blaiwes. "SIBO can be managed with dietary changes and supplemental interventions," he said. For example, taking prebiotics and probiotics can help tilt the balance of gut bacteria from "bad" to "good."

But that might not be enough, Blaiwes noted: "Depending on the severity, it may require seeking medical care and use of prescription antibiotics." Either way, if you have SIBO, you're going to want to have a healthcare provider available to talk you through these various scenarios.

What not to eat if you have small intestinal bacterial overgrowth

So what are those dietary changes Blaiwes is referring to? Intestinal bacteria seem to have a sweet tooth—so if you do, too, it's time to put the carbs and sweets down and back away slowly! "Fermentable sugars, fibers, and complex carbohydrates are the preferred foods for bacteria, so diets rich in these nutrients should typically be avoided while rebalancing bacterial overgrowth," he explained.

A good rule of thumb is to try the low-FODMAP diet, but that's not the only diet that's recommended for SIBO suffers. The Specific Carbohydrate Diet—which bans all sweets, grains, milk products and starches—and the all-liquid Elemental Diet (done on a temporary basis only) are also options.

Is SIBO permanent?

If you have SIBO now, does that mean you'll always have it? "No, unwanted bacteria throughout the GI tract, including SIBO concerns can be managed via multiple approaches," Blaiwes affirmed. Some good news, at last!

But with one caveat: it can come back. "As SIBO is often associated with other underlying GI concerns," Blaiwes said, "SIBO can re-occur after treatment or remain a long-term issue for some."

References

• Ahmed JF, et al. "Aetiology, diagnosis and management of small intestinal bacterial overgrowth." Frontline Gastroenterology. February 2023. https://fg.bmj.com/content/14/2/149
• Malik Z. "Small Intestinal Bacterial Overgrowth (SIBO)." Merck Manual. March 2023. https://www.merckmanuals.com/professional/gastrointestinal-disorders/malabsorption-syndromes/small-intestinal-bacterial-overgrowth-sibo
• "(SIBO) Small Intestinal Bacterial Overgrowth." Cleveland Clinic. September 2021. https://my.clevelandclinic.org/health/diseases/21820-small-intestinal-bacterial-overgrowth-sibo