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Written by
Chanel Dubofsky
Medically Reviewed by
Dr. Deb Matthew

Adjusting your diet to address and ease health concerns and symptoms can be stressful. How do you know if you're eliminating or limiting the right foods? How long do you have to wait until you start feeling better? For starters, it's essential to know the underlying cause of your symptoms, so it can be addressed effectively. If you have SIBO, also known as small intestinal bacterial overgrowth, there are nutritional adjustments that could reduce your symptoms. (Source

In this article, we'll explain what SIBO is, what causes it,  what dietary changes might help you in feeling better, and how our WellTheory NTPs can support in healing your symptoms.

What Is SIBO? 

Gut bacteria (also known as the gut microbiome) play a vital role in the immune system — in fact, 70% of your immune system is located in your gut. Small intestinal bacterial overgrowth is the overabundance of these vital microorganisms. In the small intestine gastric acid, bile, enzymes, and immunoglobulins (antibodies) normally keep bacterial growth under control. If the function of these chemicals is disrupted, or if the movement of contents from the small intestine into the large intestine is impaired or slowed, more bacteria than normal may grow in the small intestine. This can inhibit the body's ability to absorb and digest nutrients. (Source, Source)

What Causes SIBO? 

There are a number of potential root causes of SIBO, including: 

  • complications from gastric bypass surgery, or gastrectomy (performed in order to treat peptic ulcers and stomach cancer) (Source, Source)
  • problems with the structure of the small intestine, such as intestinal adhesions (scar tissue) and intestinal diverticulosis (tissue that protrudes through the wall of the small intestine) (Source)
  • medical conditions, such as Crohn's disease, celiac disease, and irritable bowel syndrome (IBS) (Source, Source, Source)

Other conditions and factors that may also be associated with SIBO include: 

  • age: The likelihood of SIBO occurring increases with age because the digestive system slows down over time, and the probability of surgeries, anatomical problems, and medical procedures increases. In one study of 328 subjects, 294 of them aged 61 or older, SIBO was diagnosed in 15.6% of older adults, compared with 5.9% in subjects aged 24 to 59. (Source)
  • chronic pancreatitis: Pancreatitis is the inflammation of the pancreas. When it reoccurs and becomes chronic, it can cause damage to the pancreas and cause digestion problems. In one study, SIBO was a complicating factor in up to 67% of cases of chronic pancreatitis. (Source, Source)
  • cirrhosis: Cirrhosis is scarring of the liver that occurs as it attempts to repair injury caused by disease, excessive alcohol consumption, or another condition. Cirrhosis is associated with intestinal dysmotility, a condition in which the muscles in the digestive system become impaired and slow down the rate of digestion, causing food to be trapped in the intestine. Patients with cirrhosis are at high risk of developing SIBO, and the more severe the cirrhosis, the more likely they are to have it. (Source, Source, Source)
  • cystic fibrosis (CF): Gastrointestinal issues are common in those with cystic fibrosis, a genetic disorder that impacts breathing and digestion. SIBO has been detected in 30%–50% of CF patients. (Source, Source)
  • fibromyalgia: A study published in the journal Pain in November 2019 revealed that an abnormal gut microbiome had been found in patients with fibromyalgia, a disorder characterized by musculoskeletal pain, as well as issues with sleep, memory, and mood. In women with fibromyalgia, 19 significant differences were found in their gut microbiome species. Fibromyalgia has been linked to SIBO, as well as IBS. (Source, Source, Source
  • hypothyroidism: If you have hypothyroidism, your thyroid isn't producing enough thyroid hormone. Those with hypothyroidism have been found to have slower activity in the small intestine, and SIBO is common. (Source, Source

Small intestinal bacterial overgrowth is often the result of a medical procedure or condition that slows down the passage of food in the digestive tract, allowing gut bacteria to collect and grow. Therefore, it's vital to understand the underlying cause of SIBO in order to treat it effectively. While SIBO has primarily been associated with patients who have motility disorders and structural issues within the GI tract, it is now thought to be much more prevalent and vastly undiagnosed. (Source, Source

What Is SIBO's Impact on the Body? 

In addition to making you feel less than great, untreated SIBO can lead to a number of health problems, including: 

  • dehydration as a result of chronic diarrhea and loss of fluids 
  • weight loss caused by malabsorption of nutrients 
  • excess bleeding or other problems due to deficiencies in fat-soluble vitamins such as vitamins A, D, and E. Those with SIBO struggle to absorb these vitamins, and may be deficient in Vitamin B12, which is metabolized by bacteria.
  • osteomalacia (softening of the bones) and/or osteoporosis (weak and brittle bones), also due to poor absorption of calcium 

Managing your SIBO symptoms can be taxing on your energy and may lead to anxiety and depression, so it's important to be mindful of overall health when getting treatment. (Source, Source

Symptoms of SIBO 

A SIBO diagnosis is based on the symptoms presented. Common symptoms include: 

  • bloating 
  • abdominal discomfort 
  • diarrhea, sometimes severe. Some also experience steatorrhea, stool that is light-colored, soft, bulky, greasy, and very bad smelling.
  • weight loss 
  • fatigue 
  • nausea
  • constipation
  • symptoms of malnutrition 
  • excess flatulence 


It is important to note that not everyone with SIBO has symptoms, and SIBO often goes underdiagnosed in clinical settings. 

How Is SIBO Diagnosed? 

Your health care provider will take a medical history, which will include questions about your diet, and conduct a physical exam, including a blood test to check for vitamin deficiencies. There are also a number of specific tests they may conduct: 

  • stool evaluation to determine if your body is absorbing fat normally 
  • imaging tests such as X-rays and MRI, to check for any anatomical abnormality in the small intestine 
  • small intestine aspirate and fluid culture, considered the "gold standard" for diagnosing SIBO. This invasive test uses an endoscope (a long, flexible tube placed down the throat) to obtain a sample of intestinal fluid, which is evaluated for bacterial growth.
  • breath testing. For this test, you drink a solution that's a combination of glucose and water, and then breathe into a breathalyzer. A rapid rise in the amount of methane or hydrogen emitted into the breathalyzer may mean bacteria is fermenting in your intestines, indicating overgrowth. 


How Is SIBO Treated? 

Correcting the underlying cause of SIBO is of the utmost importance when it comes to treatment. The bacterial overgrowth must be managed, and damage from malnutrition and vitamin deficiency addressed. 

Depending on the source of SIBO, a health care provider may opt for: 

  • Nutritional support is essential to quickly and effectively handle the weight loss and malnutrition that can come with SIBO. This usually involves dietary changes and use of supplements. 
  • Antibiotics may be used to reduce the overgrowth of bacteria, although this may cause unwanted side effects such as diarrhea. While antibiotics usually have a relatively quick impact, we recommend individuals try a holistic treatment that includes supplements and changes to diet. 
  • Surgery may be needed if the cause of SIBO is injury or an abnormality in intestinal structure. 

(Source, Source

The SIBO Diets

There’s no one diet that works for everyone with SIBO, and you’ll want a health care provider's guidance before starting any kind of nutrition modification. That being said, there are two diets that have been researched and shown to improve the symptoms and long-term prognosis of those with SIBO. 

The Elemental Diet 

The elemental diet is a liquid meal replacement plan, which is usually prescribed for people with severe GI tract issues. The goal of the diet is to allow the digestive system to relax and heal while still providing needed nutrition including dietary building blocks — proteins, fats, and carbohydrates — that are easy to digest and will be absorbed thoroughly. 

In addition to those with SIBO, the elemental diet is recommended for: 

  • those with inflammatory and autoimmune conditions such as Crohn’s, IBS, celiac disease, arthritis, and chronic pancreatitis 
  • those with cancer, HIV, and/or anorexia, who are in need of nutritional supplementation 
  • those whose digestive systems aren't functioning fully with conditions such as short bowel syndrome (when the body isn't able to digest food sufficiently because there physically isn't enough small intestine) and pancreatic insufficiency (the pancreas doesn't generate enough digestive enzyme to digest the food in the small intestine) 

The elemental diet is not for weight loss, and people with blood sugar conditions such as diabetes shouldn't use it. It’s challenging to follow because solid foods are not permitted, and there can be physical side effects that may include: 

  • abdominal cramping, an indication that fecal matter that's been stuck in the colon is loosening (a good sign) 
  • headaches, lightheadedness, nausea, and fatigue, which may be symptoms that your liver is ridding itself of excess toxins 
  • reduced motility, or less frequent bowel movements 

In a study of 93 participants with IBS who had abnormal breath test results, 80% of those who were on the elemental diet showed an improvement in symptoms after 2 weeks. Some participants continued on the diet for another week, with 85% of participants overall seeing improvement in symptoms. (Source)

The elemental diet isn't a long-term solution, and you are meant to reintroduce foods after your digestive system has had time to rest. If you do opt for the elemental diet, your health care provider may recommend that you next move to the low FODMAP diet. (Source, Source, Source

The Low FODMAP Diet 

The low FODMAP diet is more commonly used to treat both SIBO and IBS. It's an elimination diet meant to help identify foods that may be causing symptoms. FODMAP is an acronym referring to certain carbohydrates that are poorly absorbed in the small intestine. They move intact into the large intestine, or colon, where bacterial fermentation releases excessive amounts of gas. FODMAPs may also draw large amounts of water into the GI tract, causing diarrhea. 

FODMAP stands for: 

Fermentable: Foods that your gut bacteria feeds on, and transform into gasses

Oligosaccharides: Carbohydrates formed from monosaccharides that act as prebiotics, feeding beneficial gut bacteria

Disaccharides: Carbohydrates formed from two monosaccharides, such as lactose, sucrose, and maltose

Monosaccharides: The most basic carbohydrates, such as fructose, glucose, and galactose 

Polyols: Sugar alcohols

Like the elemental diet, the low FODMAP diet is not meant to be a long-term solution. It's an elimination diet involving three steps: 

  • avoid foods that are high in FODMAPs 
  • slowly reintroduce foods to see which ones are causing symptoms
  • avoid foods that were problematic during the reintroduction

So what foods would you avoid if you were on the low FODMAP diet? 

  • fructans: found in wheat, some vegetables (artichokes, asparagus, snap peas, garlic), and some additives
  • fructose: sugar found in some fruits (dried fruit, peaches, pears, cherries), as well as high fructose corn syrup and honey 
  • galactans: found in beans, chickpeas, lentils, and other legumes
  • lactose: found in dairy products 
  • polyols: sugar alcohols that naturally occur in some vegetables (cauliflower, mushrooms), fruits (apples, blackberries), and artificial sweeteners 

It's essential that you work with a health care provider, dietician, or nutritional therapy practitioner when embarking on the low FODMAP diet (or any restrictive diet, for that matter). Many people with SIBO also have conditions such as celiac disease, diabetes, and Crohn's, so it's important to take into consideration what these coexisting diagnoses mean when making dietary changes. 

(Source, Source, Source, Source)

WellTheory's Nutrition Therapy Practitioners (NTPs) are trained in the low FODMAP diet, and are here to support and direct you if you opt for this particular nutritional protocol.

Visit our Membership page to learn how you can get personalized support from our NTPs.

The Bottom Line on SIBO Diets 

While there isn't one particular diet that works best for everyone with SIBO, treating SIBO is possible. Treatment for SIBO depends on the reason for the bacterial overgrowth, and may involve a shift in diet, nutritional supplements, antibiotics, or surgery. For those with moderate to severe SIBO symptoms nutritional changes, such as the elemental and low FODMAP diets, can provide some relief, but it remains essential to understand the underlying cause of SIBO. 

If you have concerns about gastrointestinal symptoms, don't hesitate to consult a health care provider. It is important to note that not everyone with SIBO has symptoms, and SIBO often goes underdiagnosed.

At WellTheory, you can work with a Nutrition Therapy Practitioner and a Health Coach to not only manage your SIBO but get to the root cause of your symptoms. 

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Rheumatoid Arthritis
January 6, 2023

What is the SIBO Diet?

What is the SIBO diet? Find out what SIBO is, how it is treated, and what diet is best for those diagnosed with small intestinal bacterial overgrowth.
Medically Reviwed
Written by
Chanel Dubofsky
Medically Reviewed by
Dr. Deb Matthew
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