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A Guide to Intestinal Methanogenic Overgrowth (IMO) vs. Small Intestine Bacterial Overgrowth (SIBO)

An image of bacteria in the gutAre you one of those people who often needs to be close to a bathroom? Do you regularly suffer from abdominal pain, heartburn, or constipation? Your healthcare professional may identify your symptoms as irritable bowel syndrome (IBS), which is a blanket term given to many different health issues without clear causes. IBS, and many other gut health issues, have been believed to be connected to a condition known as small intestine bacterial overgrowth (SIBO). However, new research has found that, for many people, a distinct condition known as intestinal methanogenic overgrowth (IMO) is responsible instead.

This article will focus on the differences and similarities between small intestine bacterial overgrowth (SIBO) and intestinal methanogenic overgrowth (IMO). We also cover testing options, possible causes, and natural foods and supplements that may help your symptoms.

What Causes Intestinal Methanogenic Overgrowth (IMO)?

People with IBS often experience intestinal bacteria overgrowth. SIBO is usually identified when bacteria usually found in the large intestine start growing in larger quantities in your small intestine. This may result from various scenarios, such as using medications like antibiotics, a diet that is high in sugar or carbohydrates, or even muscle scarring due to surgeries.

In the past, the medical profession used the term SIBO as a blanket phrase for all IBS symptoms for many years. However, they have quite recently made a distinction between SIBO and Intestinal Methanogenic Overgrowth (IMO), which does not occur due to any bacterial overgrowth but high archaea levels.

What Happens When You Have IMO

Archaea, which are single-cell organisms similar to bacteria in size, have a different molecular structure. They also lack a nucleus. There are two archaea species in the human gut: Methanobrevibacter smithii and Methanosphaera stadtmanae. An overgrowth of the former is more prevalent.

Methanobrevibacter smithii tends to stop the absorption and utilization of nutrients as fuel for your body. This means that foods your body would normally fully digest end up sitting on your digestive tract. It may start to rot, and the archaea then digest those carbohydrates your body would normally utilize as food. This also produces methane gas in your gastrointestinal tract. Gas can cause damage to your enteric nervous system and contribute to a leaky gut.

What Happens When You Have SIBO

On the other hand, people with SIBO have an overflow of gut bacteria. Hydrogen, a gas with preventative and therapeutic properties in your gut, is an abundant bacteria metabolite. But when you have a bacterial imbalance, bacteria could use the hydrogen and produce hydrogen sulfide. Hydrogen sulfide can interfere with normal metabolic processes, interfere with gut homeostasis, and damage the gut lining. This is a common cause of IBS.

Similarities and Differences Between SIBO and IMO Symptoms

An image of a man holding his stomach in discomfortSymptoms common to both SIBO and intestinal methanogenic overgrowth (IMO) include the following:

  • Pain or discomfort in the abdominal area
  • Feeling bloated
  • Tending to belch often
  • Malnutrition - the body not absorbing needed nutrients
  • Nausea

With regards to differences, intestinal methanogenic overgrowth (IMO), caused by archaea, tends to result in:

  • constipation,
  • skin issues
  • leaky gut
  • heartburn
  • anxiety
  • fatigue
  • muscle and/or joint pain

On the other hand, people with SIBO symptoms, resulting from bacterial overgrowth, tend to experience:

  • diarrhea
  • occasional constipation
  • weight loss

Gut Health and Your Gut Hormones

Gut health issues can impact many different parts of your body, including your hormones. It could cause estrogen dominance and is also linked to brain health. This is shown by research linking leaky gut to various central nervous system disorders like anxiety and depression, to name a few. And this makes sense when you take into consideration that about ninety percent of your body’s serotonin production takes place in your gut.

Serotonin, often referred to as the ‘happy hormone’, is a neurotransmitter used in the brain to promote feelings of wellbeing and happiness.

Along with this hormone, the gut also produces several hormones that play a critical role in metabolism and digestion:

  • Grehlin - Lesser amounts are also released in the brain and pancreas. Also referred to as the hunger hormone, grehlin sends chemical messages to your brain indicating a need for food.
  • Glucose-dependent insulinotropic polypeptide (GIP) - Secreted in response to eating, this hormone encourages the release of insulin into your bloodstream to help control your blood sugar levels.
  • Cholecystokinin (CCK) - Released after a meal, this hormone helps with the digestive process while reducing appetite.
  • Glucagon-like peptide 1 (GLP-1) - This hormone stimulates insulin secretion from the pancreas to deal with blood sugar levels.
  • Peptide YY (PYY) - This hormone is released to decrease your food intake by modulating gut motility.

While your gut releases over thirty different hormones, we cannot discuss all of them here. But what one needs as a takeaway, is that most play a significant role in your health and can affect many different parts of your body. This includes your adrenals. And SIBO and IMO can play a role in adrenal fatigue.

Identifying SIBO or Intestinal Methanogenic Overgrowth (IMO)

Knowing which condition you have is important for determining how to best address your symptoms. The bad news is that it can take a while to identify whether one of these issues is behind your symptoms. Your healthcare professional may need at least three months of health history first.

They may then suggest a few tests to discern whether you have SIBO or intestinal methanogenic overgrowth (IMO).

Tests for Intestinal Methanogenic Overgrowth (IMO)

For many practitioners dealing with gut health issues, extracting small bowel fluid and taking a bacterial count through culture is the norm. But this does not necessarily allow them to determine which of the gut conditions you have. Furthermore, the extraction process is not 100% guaranteed as the sample can be contaminated by bacteria in your mouth or esophagus.

An image of a urine sampleAnother test looks at microbial byproducts found in a urine sample. Much like the previous test, it also does not determine which of the two conditions you are dealing with exactly. It can only determine that you have an overabundance of gut flora in your small intestine.

One of the best indications of intestinal methanogenic overgrowth (IMO) is the smell of methane on your breath.

A breath test can help narrow down your diagnosis as it measures the hydrogen, methane, and carbon levels in your lungs. Higher methane levels could point towards intestinal methanogenic overgrowth.

A newer breath test, however, tests not carbon only methane, carbon dioxide, and hydrogen levels, but hydrogen sulfide levels as well. This is more helpful in identifying hydrogen sulfide-related SIBO. Before this test, it was assumed that, if tests came back negative for hydrogen and methane, symptoms must result from hydrogen sulfide-producing bacteria. However, sometimes this wasn't the case.

Breath Testing for IMO

When taking a breath test, there are certain protocols you need to follow for an accurate result ahead of time.

Preparing for the Breath Test

  • The 24-hour period before your test requires a strict diet. You are only allowed to eat baked or boiled chicken, turkey, or fish, and white rice. The only seasoning recommended is salt and pepper.
  • You should fast for 12 hours immediately before your test. During this period, you should only drink water and take prescription medications under the advice of your healthcare professional.
  • Stop taking any antimicrobial medication like antibiotics, with the permission of your doctor.
  • You should also do no exercise, stop smoking, and avoid ingesting anything that could influence bowel movements.

Understanding Your Results

When looking at your test results, your healthcare practitioner will measure them against the baseline. The baseline refers to what those in the medical profession consider normal.

If your hydrogen levels are equal to or more than 20 p.p.m. it shows a positive SIBO reading.

If your methane reading shows less than or equal to 10 p.p.m. it indicates intestinal methanogenic overgrowth (IMO). If both tests are normal, they may consider looking at your hydrogen sulfide readings.

Intestinal Methanogenic Overgrowth (IMO) and Fatigue

Fatigue is one of the most common symptoms associated with intestinal methanogenic overgrowth (IMO). This is a common symptom of many other conditions as well. Adrenal Fatigue Syndrome (AFS) is a common condition caused by chronic stress, which also causes fatigue and frequently co-occurs with gut issues like IBS, SIBO, and IMO. Gut issues can also lead to chronic inflammation and a cascade of related problems.

There is, though, much you can do to not only boost your energy levels but address intestinal methanogenic overgrowth (IMO) and adrenal fatigue as well.

Natural Remedies for IMO

Medications, although probably the quickest way of addressing your energy levels and other symptoms, may not address the root cause of the condition. They may also cause complications. Antibiotics are a good example, which can cause problems because it does not discriminate between the gut flora causing problems and good gut flora. It wipes out it all and could leave you feeling more tired than before. Furthermore, certain antibiotics could also increase your tendency towards constipation.


An image of bags full of healthy foodYour diet plays a significant role in your recovery process. Your healthcare practitioner can help you cut out foods that may further compromise your gut health while incorporating beneficial foods. You may need to cut out sugars, processed foods, and certain carbohydrates, while incorporating more beneficial fruits and vegetables. Foods known to boost your energy levels include dark chocolate, whole grains, coconut, omega fatty acids commonly found in fatty fish, ginger tea, and eggs.


Some herbal supplements, like allicin, a compound derived from garlic, may help to kill off the bad intestinal flora while encouraging the growth of beneficial flora.

Supplements to consider that promote hormone and gut health, support adrenal health, and may help boost your energy levels include, amongst many others:

  • Folic acid – helps address central nervous system issues
  • Vitamin B12 – gives you an energy boost and improves thinking
  • Selenium – helps your body deal with oxidative stress
  • Probiotics – encourage a balanced gut microbiome
  • Chromium – helps your body better metabolize food

However, be aware that works for one person does not necessarily work for another. Always talk to your healthcare professional before making any major changes to your diet, supplements, or lifestyle, especially if you have other health conditions like SIBO, IMO, or AFS, which can make your body more vulnerable to unexpected reactions.


When considering any course of action in addressing intestinal methanogenic overgrowth (IMO), please do so with the guidance of a qualified healthcare professional. It's important to consider your level of adrenal fatigue as well. Sudden changes to your diet or new supplements could end up doing more harm than good. Also, some people are more sensitive than others. Addressing your gut condition, as well as adrenal fatigue and any other possible root causes, will not only help promote gut health but may help resolve other health issues and imbalances as well.

In Closing

Intestinal methanogenic overgrowth (IMO) could result in a variety of uncomfortable health issues, like pain, bloating, heartburn, leaky gut, constipation, nausea, and fatigue. If you've had these health issues, you owe it to yourself to figure out what is causing them and take steps to heal. Here's how:

  • Start keeping a food and symptoms diary to show your health professional at your next visit.
  • Talk to your doctor about getting a breath test to identify SIBO or IMO.
  • Consider certain diet changes and supplements.

Many people in the Dr. Lam Coaching program suffer from intestinal methanogenic overgrowth (IMO). If you think your issues stem from this condition and would like to talk to someone about it, please call us at 626-571-1234 for a free initial consultation. You can also request a callback here.

© Copyright 2022 Michael Lam, M.D. All Rights Reserved.

Dr. Lam’s Key Question

Many intestinal methanogenic overgrowth (IMO) symptoms are similar to those of adrenal fatigue. And while the condition may contribute to adrenal fatigue, adrenal fatigue may also worsen the condition. This is because chronic stress often leads to gut issues and inflammation, while gut issues are a chronic stressor on your body. There are steps you can take to identify if there is a connection though.

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