If you’ve been on a continuous search for the next irritable bowel syndrome (IBS) tool to give you relief, you may have already stumbled on the Elemental Diet. You probably wondered:
- “Could this finally get rid of my bloating?”
- “Am I supposed to live on shakes only… for how long?”
Here we break down what a 14-day Elemental Diet can do for IBS, who it might and might not help, and what the studies say about it.
Firstly, What is the Elemental Diet?
An Elemental Diet provides complete nutrition through liquid formulas made with pre-digested nutrients. That means:
- Proteins are in the form of amino acids
- Carbohydrates in the form of simple sugars
- Fats in an easy-to-absorb form
- Plus, essential vitamins, minerals, and electrolytes
Because everything is already broken down, your digestive system doesn’t have to work as hard. Nutrients are absorbed quickly in the upper small intestine, which means:
Your body still gets fed, but
- Much less “leftover” food moves further down the small intestine
- Overgrown microbes have a lot less to ferment (and therefore can start to “die off”)
In other words: the goal is to starve the overgrowth of certain “gut bugs” that might be behind stubborn bloating, abdominal pain, fatigue, and altered bowel habits, while still feeding you.
Unlike long-term lifestyle changes, the Elemental Diet is meant to be temporary. It typically involves taking these elemental formulas (usually a powder mixed with water) as your sole source of nutrition for about 14 days, under the supervision of your healthcare provider.
This is a medical nutrition therapy; not a “cleanse.”
IBS Subtypes and Bacterial Overgrowth
There are 4 main IBS subtypes:
- IBS-D: Diarrhea-predominant
- IBS-C: Constipation-predominant
- IBS-M: Mixed bowel habits: AKA cycling between diarrhea and constipation
- IBS-U: Unclassified, or doesn’t fit neatly in the other categories above
Beyond stool form, these subtypes may be associated with different patterns of bacterial overgrowth, such as:
- Small Intestinal Bacterial Overgrowth (Hydrogen Dominant SIBO)
- Intestinal Methanogen Overgrowth (IMO)
- Intestinal Sulphide Overproduction (ISO)
1. IBS-D
Most commonly associated with:
- Hydrogen-dominant SIBO: This type of SIBO may affect about 50% of people with IBS-D. Hydrogen itself is not linked with diarrhea or constipation, but hydrogen-producing bacteria are common in IBS-D. That hydrogen can then be used by other organisms in the gut, which do influence stool form.
- Sometimes hydrogen-sulfide producing bacteria (which can lead to ISO (Intestinal Sulphide Overproduction). Hydrogen-sulphide gas is naturally created in the gut, but amounts that exceed the norm have been linked to loose stools, familiar to those in the IBS-D subtype. Not all breath tests currently measure for hydrogen sulphide, but a three-gas breath test, or potentially a healthcare provider skilled in reading hydrogen methane breath tests, in combination with a patient’s symptoms, may help provide clues as to whether ISO is a possibility.
- While rarer (at a mere estimated 17% of those with IBS-D) IMO can affect those with IBS Diarrhea.
2. IBS-C
Most commonly associated with:
- Methanogen overgrowth or IMO: This may affect about 50% of people with IBS-C, and can occur along both the small and large intestine (hence the term “IMO”). Methane gas is associated with slower gut motility and constipation, and methanogens (the single-celled organisms that produce this methane gas) are technically not bacteria.
- Potential combination SIBO: Methanogens use hydrogen produced by other bacteria to make methane. Therefore, you can have both hydrogen-producing bacteria (which feeds hydrogen to methane-producing organisms) and methane-producing “archaea”.
- While rarer, it is possible to be constipation predominant and have one’s breath test return with only an elevated Hydrogen within 90 minutes (aka SIBO).
3. IBS-M
Save this article
Enter your email address and we'll send it straight to your inbox.
This subtype may have either SIBO or IMO, or a combination of both. Either SIBO or IMO may affect 25% of people with IBS-M. The resulting gasses may speed up or slow down the gut.
Aside from stool form, symptoms of SIBO, IMO and/or ISO that overlap with IBS include:
- Bloating
- Gas
- Abdominal distention
- Abdominal pain
Elemental Diet for SIBO and IMO
In the early 2000s, a study looked at people with IBS who had a positive breath test suggesting bacterial overgrowth. Participants followed an exclusive Elemental Diet for 14 days (up to 21 days for some).
Results include:
- Normalized breath tests in 85% of participants
- Symptom improvement in participants whose breath test results normalized compared to those whose test did not normalize.
A more recent study in adults with positive breath tests for IMO, SIBO, or both after a 14 day Elemental Diet found:
- 58% of participants with IMO only normalized their breath test
- 100% of participants with SIBO only normalized their breath test
- 75% of participants with both IMO and SIBO normalized their breath test
In this study, the elemental formula was tolerated by all participants, and 83% reported adequate overall symptom relief 2 weeks after the Elemental Diet concluded.
Elemental Diet for IBS
Another recent study looked at people with IBS who followed a 2-week exclusive Elemental Diet, then returned to their usual diet over the next 2 weeks. The results include:
- 73% of participants had at least a 30% reduction in abdominal pain
- 50% of participants had at least a 50% reduction in abdominal pain
- Overall, 82% of participants experienced at least a 30% improvement in abdominal pain, discomfort, distension, or bloating.
So, even when the focus is on IBS symptoms, without a confirmation of SIBO or breath test levels, a 14-day Elemental Diet may be a tool for symptom relief.
Who Might Benefit From a 14-day Elemental Diet?
An Elemental Diet can be considered for people who:
- Have SIBO, IMO, or both, and:
- Want an alternative to antibiotics or have not responded well to antibiotics
- Have IBS, and:
- Have not had sufficient symptom improvement with other interventions
- Have NO major red flags
Other studies have also suggested use of Elemental Diets for other conditions, such as inflammatory bowel disease (IBD), eosinophilic esophagitis, or eosinophilic gastroenteritis.
Who Might the Elemental Diet NOT Be For?
This diet is not for everyone. In all cases, always consult your healthcare provider before starting an Elemental Diet.
The Elemental Diet may not be appropriate for certain people, including:
- Children under the age of 12
- Those who are pregnant or nursing
- Those with diabetes, pre-diabetes, or any history of unstable blood sugars (such as reactive hypoglycemia) as Elemental Diets are predominantly carbohydrate-based
- Those who have a history of an eating disorder
Key Takeaways
- A 14-day Elemental Diet is a short-term, medically supervised liquid nutrition plan that provides fully pre-digested nutrients, aiming to “feed you while starving overgrown gut microbes.”
- By being absorbed quickly in the upper small intestine, elemental formulas leave less food for microbes lower down, which may help reduce bacterial overgrowth linked with IBS symptoms like bloating, pain, and altered bowel habits.
- Different IBS subtypes (IBS-D, IBS-C, IBS-M, IBS-U) often correlate with different gas patterns and overgrowths, such as hydrogen-dominant SIBO, intestinal methanogen overgrowth (IMO), and sulphide overproduction (ISO)- all of which can overlap with IBS symptoms.
- Research in people with positive breath tests for SIBO/IMO shows that a 14-day Elemental Diet can normalize breath tests in a majority of cases and is often associated with meaningful symptom relief.
- In IBS more broadly (even without confirmed SIBO), a 2-week exclusive Elemental Diet has been shown to reduce abdominal pain and improve bloating/distention in most participants, suggesting it can be a tool for symptom relief when other approaches haven’t been enough.
- A 14-day Elemental Diet may be considered for adults with IBS, SIBO, and/or IMO who don’t respond well to or prefer to avoid antibiotics and who have no major red-flag symptoms, always under healthcare supervision.
- The Elemental Diet is not appropriate for everyone; particularly children under 12, those who are pregnant or nursing, people with diabetes or unstable blood sugars, and those with a history of eating disorders.
References:
- Villanueva-Millan, M. J., Leite, G., Wang, J., Morales, W., Parodi, G., Pimentel, M. L., Barlow, G. M., Mathur, R., Rezaie, A., Sanchez, M., Ayyad, S., Cohrs, D., Chang, C., Rashid, M., Hosseini, A., Fiorentino, A., Weitsman, S., Chuang, B., Chang, B., Pimentel, M. (2022). Methanogens and hydrogen sulfide producing bacteria guide distinct gut microbe profiles and irritable bowel syndrome subtypes. American Journal of Gastroenterology, 117 (12), 2055–2066. https://pubmed.ncbi.nlm.nih.gov/36114762/
- Pimentel, M., Constantino, T., Kong, Y., Bajwa, M., Rezaei, A., & Park, S. (2004). A 14-day elemental diet is highly effective in normalizing the lactulose breath test. Digestive Diseases and Sciences, 49(1), 73–77. https://doi.org/10.1023/b:ddas.0000011605.43979.e1
- Rezaie, A., Chang, B. W., de Freitas Germano, J., Leite, G., Mathur, R., Houser, K., Hosseini, A., Brimberry, D., Rashid, M., Mehravar, S., Villanueva-Millan, M. J., Sanchez, M., Weitsman, S., Fajardo, C. M., Rivera, I. G., Joo, L., Chan, Y., Barlow, G. M., & Pimentel, M. (2025). Effect, tolerability, and safety of exclusive palatable elemental diet in patients with intestinal microbial overgrowth. Clinical Gastroenterology and Hepatology, 23 (12), 2306–2317.e7. https://doi.org/10.1016/j.cgh.2025.03.002
- Rezaie, A., Joo, L., Hosseini, A., et al. (2026). Abdominal pain response to a two-week exclusive palatable elemental diet in irritable bowel syndrome: Post hoc analysis of a prospective trial. Gastroenterology, 170 (6), S355–S356.
- Nasser, J., Mehravar, S., Pimentel, M., Lim, J., Mathur, R., Boustany, A., & Rezaie, A. (2024). Elemental diet as a therapeutic modality: A comprehensive review. Digestive Diseases and Sciences, 69(9), 3344–3360. https://pubmed.ncbi.nlm.nih.gov/39001958/
