Is this the Cause of Belly Bloat?

Updated on: November 1, 2022

Hypothesis and Emerging Research

Some early observations support this concept (or parts of the theory), and there is scientific interest in elucidating exactly what’s at work.

If you regularly feel bloated after eating, functional medicine practitioner and women’s health expert Amy Myers, M.D. says it could be caused by SIBO—small intestinal bacterial overgrowth, i.e. an excess of (good) bacteria in the small intestine. (It goes without saying that there are other causes of bloating, from the benign, like a junk food binge, to the serious, like ovarian cancer.) Myers sees SIBO in about 20 percent of patients—most of whom have chronic health issues—at her Austin clinic, but she says that SIBO is on the rise in seemingly healthy people. We asked her about the causes of SIBO, its connection to leaky gut, related symptoms, and of course, how to test for and treat SIBO, as well as how to keep your microbiome balanced in the first place.

For more from Myers on goop, see this immune system reboot, her protocols for healing from Candida (yeast overgrowth) and thyroid dysfunction, plus her tips for avoiding autoimmunity.

A Q&A with Amy Myers, M.D.

What is SIBO?

We have good bacteria in our small intestine (the upper gut), but too much of it can throw our microbiome out of balance, which is a bad thing. Small intestinal bacterial overgrowth (SIBO) is an overgrowth of bacteria in the small intestine. (More technically, a bacterial population greater than 10⁵-10⁶ organisms/mL in the small intestine.)

What causes bacterial overgrowth?

It usually follows a disruption of the gut bacteria, and the main culprits in that are 1) high-carb, high-sugar, high-alcohol diets and 2) medications like antibiotics, acid-blocking drugs, and steroids.

“We have good bacteria in our small intestine (the upper gut), but too much of it can throw our microbiome out of balance, which is a bad thing.”

Nerves, muscles, and neurotransmitters move food—and bacteria with it—through the digestive tract, from the stomach to the small intestine and into the colon. When there’s a breakdown in gut motility (the movement of the gut or things through it), bacteria can build up in the small intestine. (When gut motility is too fast, you might have diarrhea, and if it’s too slow, you might feel constipated. But you can have gut motility issues without either symptom.) Breakdowns can be the result of damage to your gut nerves or muscles (this can be caused, for example, by diabetes or autoimmune conditions such as scleroderma) and physical obstructions (like surgery scars or Crohn’s disease), as well as the dietary/drug causes above.

How widespread is it, and who does it affect?

There aren’t conclusive statistics. One study found the prevalence of SIBO to be about 6 percent in a control group of healthy individuals. In my clinic—where I’m seeing people with chronic health issues such as autoimmunity that themselves can disrupt gut motility—I see SIBO in about 15 to 25 percent of patients.

SIBO has primarily been observed in people with chronic gut motility problems, and with neurologic disorders or diabetes that can lead to dysfunction in the nerves that line the gut. But we’re seeing it more in otherwise seemingly healthy people. It’s not clear whether that’s due to better diagnostic testing or other reasons (like high-carb diets).

There is also evidence of correlations between SIBO and low stomach acid, hypothyroidism, and IBS—all of which are associated with disrupted gut motility.

“We’re seeing it more in otherwise seemingly healthy people. It’s not clear whether that’s due to better diagnostic testing or other reasons (like high-carb diets).”

What are the primary symptoms of SIBO?

Bloating is the #1 symptom. People affected by SIBO will typically say, “I ate a meal and then looked 6 months pregnant.”

Other than bloating, some people experience gas, abdominal pain, diarrhea, and/or constipation.

I also see people with food intolerances (such as gluten), chronic illnesses (such as fibromyalgia), chronic fatigue syndrome, and, as mentioned, neuromuscular disorders and diabetes, who come down with it.

Other complications can include nutritional deficiencies, and fat or carbohydrate malabsorption because nutrients are partially absorbed in the small intestine, which isn’t working properly if you have SIBO. So, with SIBO, you could potentially become B12-deficient, or deficient in some of the fat-soluble vitamins like, D, A, K and E.

“Bloating is the #1 symptom. People affected by SIBO will typically say, ‘I ate a meal and then looked 6 months pregnant.’”

If a patient has a histamine intolerance, I’ll also think to check for SIBO, which can be an underlying cause, as the overgrowth of bacteria can produce excess histamine from undigested food.

Some studies looking at the bowels of people with SIBO have found mucosal inflammation, mucosal thinning, an increase in lymphocytes, and even some blunting of the villi (on the surface of the intestines), which is typically seen in celiac patients.

What is the relationship between leaky gut and SIBO?

SIBO can be an underlying cause of leaky gut (when the junctions in the intestinal lining break apart, and particles including toxins and undigested food escape from your intestines and travel throughout your body via your bloodstream). If you have SIBO and it has been left untreated for a long period of time, then you’re certainly at risk for leaky gut. But you can also get leaky gut from Candida overgrowth, eating gluten or having other food intolerances, infections like intestinal parasites, medications (i.e., acid-blocking, antibiotics, and ibuprofen), and toxins (like mercury and lead).

How do you test for SIBO?

The primary way to test for SIBO is a fairly complex breath test. Typically, before the test, patients follow a specific diet, avoiding carbohydrates (like grains, pastas, breads) and fasting overnight. During the test, you breathe into a small balloon and your levels of hydrogen and methane are measured, as bacteria can be hydrogen- or methane-producing. Your baseline levels are compared to your levels after ingesting sugar during the test (typically lactose or mannitol). Breath samples are taken about every 15 minutes for a few hours.

At my clinic, we use the functional medicine lab’s organix dysbiosis test, which is a urine test that looks at by-products of yeast and bacteria in the small intestine. Another functional medicine lab test that can detect elevated levels of good bacteria is the comprehensive stool test (which looks at the flora of the large intestines).

Is yeast typically associated with bacterial overgrowth?

There is some overlap between yeast overgrowth (Candida) and bacteria overgrowth (SIBO). Both are the result of a disruption in the microflora or microbiome. Both feed off of carbohydrates, so anyone who is drinking a lot of alcohol and eating a lot of sugary foods (simple carbs) is at risk for candida and SIBO. Even eating complex carbs can potentially heighten risk, as they ultimately turn into simple carbs and feed these infections. There are studies showing that people with low IgA (your immune system in your gut) can lead to SIBO, and I’ve seen that Candida can also cause low IgA.

Yeast overgrowth seems to be much more systemic, though—with symptoms like brain fog, rashes, fatigue, and body aches. SIBO tends to be much more digestive-related, i.e. bloating.

What are the treatment options?

The standard treatment is Xifaxan, which is a prescription antibiotic (a derivative of Rifaximin) that seems to be fairly specific to the gut and the gut microbiota. It’s not well absorbed throughout the body and it’s not as problematic in terms of long-term health as other antibiotics can be. (While many antibiotics can disrupt microbiome balance, it may sometimes be necessary to use an antibiotic to kill good bacteria when there’s an overgrowth.) Xifaxan can be very expensive; insurance is now beginning to cover it as a IBS drug, but prior to that, it was difficult to get coverage at all.

Other doctors may prescribe other antibiotics—such as Doxycycline, Cipro, Amoxicillin, or Flagyl—but I’ve seen the best results in my clinic with Xifaxan.

However, as mentioned, there are two types of gas that SIBO can produce, hydrogen or methane, and the hydrogen-producing bacteria seem to respond better to the Xifaxan. There have been some studies showing that the methane-producing bacteria don’t respond as well, so I typically prescribe an antibiotic called Neomycin for these patients.

Herbs can also be used to treat SIBO, sometimes in place of antibiotics, depending on the patient, the severity of the overgrowth, and what works best for them.

“It’s important to fix the underlying cause of SIBO—otherwise it can come back.”

I always get patients on a lower-carb diet, and figure out if there are any underlying causes leading to slow gut motility that can be addressed. If they do have slow gut motility and some sort of neurologic disorder, I might prescribe what’s called a pro-kinetic agent, which helps speed up the gut so bacteria doesn’t stall and build up in the small intestine.

It’s also important to address any vitamin deficiencies.

What kind of diet do you recommend for getting rid of SIBO?

The diet is very similar to what I recommend for patients with Candida. For thirty days, cut out simple carbs (i.e. sugar and processed foods) and limit your complex carbs and fruits to 1 cup a day. Initially, steer clear of fermented foods, which feed good bacteria and yeast.

What about herbs and supplements?

To help support a balanced and healthy gut microbiome, we use a blend of herbs called Microb-Clear, which is made up of magnesium caprylate, berberine, and extracts from tribulus, sweet wormwood, barberry, bearberry, and black walnut.

If patients are on a complex or complete probiotic (typically includes lactobacillus), we will take them off, because the lactobacillus probiotic adds to the bacteria population and can create more problems when there is already an overgrowth. Instead, I recommend soil-based organisms because they do not contain lactobacillus and therefore don’t add to the overpopulation of this type of bacteria.

How long does it take to heal from SIBO? Anything that is important to prevent future bacterial overgrowth?

It depends on a variety of factors. In general, you can treat SIBO with antibiotics like Neomycin and Xifaxan for ten days. If you’re going to use herbs, then we usually recommend thirty days. In my patient population, we see that for some the antibiotics work better, and for others the herbs work better. I use herbs a lot in my clinic; patients often prefer them to antibiotics, which can be expensive and aren’t always effective.

In any case, it’s important to fix the underlying cause of SIBO—otherwise it can come back. If it was eating a lot of carbs, then you should not go back to a high-carb diet. If it was hypothyroidism, then we need to treat the hypothyroidism.

To help maintain a balanced microbiome and prevent overgrowths of bacteria in the first place, I follow what I call a 4R program, which boils down to:

Remove the bad—inflammatory foods, infections, anything that irritates your gut.

Replace the good—all the ingredients that help you properly digest and absorb nutrients.

Reinonculate—take a high quality probiotic and also get in prebiotics, like high soluble fiber foods (for example, artichokes, cultured veggies, and other fermented foods).

Repair—good supplements for supporting gut health include L-Glutamine and collagen.

Amy Myers, M.D. specializes in women’s health issues, particularly autoimmunity, thyroid dysfunction, and gut health. She is the New York Times bestselling author of The Autoimmune Solution and The Thyroid Connection. She sees patients from around the world in her functional medicine clinic Austin UltraHealth, based in Austin, Texas. Dr. Myers developed the goop vitamin and supplement protocol, Balls in the Air, designed to keep us on our A game. You can get Dr. Myers’ complimentary 35 Gut Recovery Recipes eBook here.

The views expressed in this article intend to highlight alternative studies and induce conversation. They are the views of the author and do not necessarily represent the views of goop, and are for informational purposes only, even if and to the extent that this article features the advice of physicians and medical practitioners. This article is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice.