Intestinal Bacterial Overgrowth (IBO) is a common functional condition due to excessive amounts of bacteria in the gastrointestinal tract. These bacteria ferment ingested food resulting in the production of hydrogen, methane, and carbon dioxide which subsequently can induce GI symptoms including abdominal pain, bloating, distention, diarrhea and constipation. Typically this condition is treated with antibiotics but for a portion of patients symptoms often recur. Recent work suggests that increased methane production may emanate from overgrowth of a specific type of archaebacteria, causing the aforementioned symptoms. However, no current therapies exist to treat this phenomenon. The investigators propose to trial the supplement Atrantil on patients with IMO in order to study the supplements impact on symptoms, quality of life, and methane levels.

Intestinal microbial overgrowth is associated with multiple gastrointestinal symptoms. Most prevalent are gas-related symptoms (i.e. bloating, distention, increased flatus, constipation)

. Intestinal microbial overgrowth can currently be divided into two main subcategories: small intestinal bacterial overgrowth (SIBO) and intestinal methanogenic overgrowth (IMO). Both are most commonly detected via breath testing-a simple non-invasive study

• Despite the increasing prevalence of this disorder few evidence-based therapeutics currently exist. SIBO, identified by elevations in breath hydrogen, has been shown to respond to treatment with antibiotics including rifaximin and doxycycline in clinical trials
• However, IMO, detected by elevations in breath methane is a different disorder attributed to overgrowth of archaea which reside predominately in the colon
• Currently, there are no evidence-based treatments for IMO, and the American College of Gastroenterology guideline on the diagnosis and treatment of SIBO makes no specific recommendations regarding the treatment of this disorder.

Atrantil is a medical food composed of peppermint, quebracho tree bark, and horse chestnut.

These components are purported to reduce methane production, scavenge hydrogen (thus reducing the building blocks for methane), and potentially act as a cidal agent for methanogenic archaea. In a small randomized controlled-trial, Atrantil reduced bloating and constipation in a population of individuals with irritable bowel syndrome with constipation (IBS-C)

Given these initial results the investigators hypothesize that Atrantil may represent an inexpensive and safe treatment for patients with excessive methane production. Thus, the purpose of this study is to determine whether the holistic treatment, Atrantil, is beneficial for the treatment of IMO.

Inclusion Criteria:

1. Participants must be able to provide informed consent
2. Participants must be able to attend study visits
3. Participants aged 18 years or greater
4. Must have a diagnosis of Intestinal Methane Overgrowth based on North American Consensus/American College of Gastroenterology established cutoffs
5. Participants must report current symptoms of bloating, distention, abdominal pain, abdominal discomfort and constipation
6. Participant must be an established patient at Northwestern Memorial Hospital

Exclusion Criteria:

1. Participants who are already taking Atrantil
2. Participants who are pregnant or breast-feeding
3. Participants who cannot tolerate or are unwilling to complete a hydrogen-methane breath test at week 4.
4. Inability to attend all study visits and complete survey data.