Irritable Bowel Syndrome (IBS) is a common functional gastrointestinal disorder characterized by chronic abdominal discomfort, pain, and altered bowel habits without detectable structural abnormalities. Probiotics have gained attention as a supportive measure for this condition. Among these, the bacterium Bifidobacterium infantis 35624 is one of the most thoroughly researched strains for its targeted support of the gut-brain axis. This analysis explores the latest scientific understanding of this specific strain and its documented role in managing IBS symptoms.
Identifying the Specific Bifidobacterium Infantis Strain
The unique designation “35624” appended to the species name Bifidobacterium infantis is crucial because probiotic benefits are highly strain-specific. Benefits demonstrated by one strain cannot automatically be attributed to another, even within the same species. This particular strain was originally isolated from the gastrointestinal tract of a healthy human.
Its taxonomic classification has undergone recent refinement based on genomic sequencing. While historically known as Bifidobacterium longum subsp. infantis 35624, it has been reclassified as Bifidobacterium longum subsp. longum 35624 due to high genetic similarity with other members of the longum subspecies. Despite this scientific reclassification, the strain is widely recognized and marketed under its original name. The 35624 designation ensures consumers receive the exact organism studied in clinical trials.
Mechanism of Action in Reducing IBS Symptoms
The effectiveness of B. infantis 35624 is attributed to its ability to interact directly with the host’s immune and nervous systems. One primary mechanism involves anti-inflammatory effects within the gastrointestinal tract, as the strain modulates the host’s cytokine profile.
Research suggests the strain can normalize the ratio of anti-inflammatory cytokines (e.g., Interleukin-10) to pro-inflammatory cytokines (e.g., Interleukin-12), which are often dysregulated in people with IBS. This immunomodulatory action extends beyond the gut, as studies have observed a reduction in plasma levels of inflammatory markers like C-reactive protein. This reduction in systemic inflammation may contribute to overall symptom relief.
The strain also influences the integrity of the gut barrier. Dysfunction in this barrier can lead to increased permeability, which allows substances to pass through and trigger localized immune responses associated with IBS pain. By strengthening the tight junctions between epithelial cells, B. infantis 35624 helps maintain a more robust barrier, reducing unwanted permeability.
The strain contributes to gut health by producing beneficial metabolites. It ferments non-digestible carbohydrates, resulting in the creation of Short-Chain Fatty Acids (SCFAs), such as butyrate. Butyrate is a primary energy source for colonocytes, supporting the health and function of the gut barrier. SCFA production is believed to play a role in reducing the heightened pain response, known as visceral hypersensitivity, common in IBS patients.
Clinical Efficacy and Recent Trial Insights
The initial efficacy of B. infantis 35624 was established through several placebo-controlled trials. A landmark study involving women with mixed IBS subtypes confirmed that a specific dosage was superior to placebo in alleviating core symptoms, including abdominal pain, bloating, distension, and altered bowel movements.
This trial determined a unique dose-response relationship: the most effective dosage was 1 x 10^8 colony-forming units (CFU), while both lower and higher doses were less effective. The improvement in symptom assessment for the successful dose exceeded placebo by more than 20%. These findings led to the strain being included in international clinical guidelines for IBS management.
More recent analyses have provided a nuanced view of the strain’s standalone efficacy. A 2017 meta-analysis found that while single-strain studies showed inconsistent results, the strain was highly effective when included in composite probiotic formulations. This suggests that the full benefit of B. infantis 35624 may be realized when it works synergistically with other complementary bacteria.
The latest insights emphasize that the strain’s ability to improve symptoms like abdominal pain and bloating results from its anti-inflammatory and gut-modulating properties, not simply altered bowel transit time. Its effectiveness in reducing abdominal distention has remained a consistently positive finding across multiple studies. This research confirms that B. infantis 35624 has a measurable impact on IBS symptoms.
Practical Considerations for Consumer Use
For individuals considering this strain for IBS support, understanding the proper administration and safety profile is important. The typical clinically supported dosage for B. infantis 35624 is 1 x 10^8 CFU, administered once per day, though some commercial formulations use 1 x 10^9 CFU. Consistency is paramount, as the beneficial effects are transient, meaning the strain’s population levels return to baseline once supplementation stops.
The strain is safe and well-tolerated, with a safety profile comparable to placebo in clinical trials. Adverse effects are typically mild and transient, such as temporary gas or bloating, which usually resolve within the first few days or weeks of consistent use.
The strain is commonly delivered in encapsulated form to ensure the bacteria survive the acidic environment of the stomach. Many commercial products are formulated to be shelf-stable and do not require refrigeration. Consult with a healthcare provider before starting any new supplement regimen.