Probiotic 35624 for Bloating: What the Trial Populations Change

The positive IBS trial tested three capsule doses

In 2006, 362 women with IBS were randomized to placebo or Bifidobacterium infantis 35624 capsules for four weeks. Only the 100-million-CFU daily dose significantly outperformed placebo for the primary pain/discomfort outcome. CFU counts the colony-forming units in the preparation.¹

Bloating was a secondary outcome: its adjusted score fell 0.71 points versus 0.44 with placebo, on a 0–5 scale. The highest-dose capsule, 10 billion CFU, clumped in later laboratory testing. Its disappointing result cannot establish that a higher bacterial dose is inherently worse.¹

This was short-term IBS research, not a trial of every cause of bloating or every capsule sold today.¹

The larger bloating trial found no advantage in severity

A 2017 publication reported a US trial that randomized 302 people, with 275 providing evaluable data. Participants had recurring discomfort and bloating but had not sought a physician’s care or prescription treatment for those symptoms in the previous year.²

After four weeks of one billion CFU/day, mean discomfort and bloating severity did not differ significantly from placebo. The probiotic group did have more bloating-free days, a separate favorable outcome. Both groups improved over time.²

The favorable frequency result does not turn the severity result into a positive finding.²

A newer functional-bloating trial also needs its treatment sequence explained

The November 2025 study³ enrolled people meeting Rome IV criteria for functional abdominal bloating. It reported 68 evaluable participants, 34 per group, receiving 100 million CFU or placebo for four weeks after a two-week metronidazole phase.³

Bloating and quality of life improved in both groups. No significant between-group differences remained after correction for multiple comparisons. Improvements found only within the probiotic group for selected symptoms do not establish superiority over placebo.³

The antibiotic lead-in also limits how directly this applies to buying a probiotic alone. The publisher’s accessible abstract reports the results; the full methods are subscription-only.³

Detecting the strain in stool is a different outcome

A 2013 study⁴ compared 39 people with IBS receiving the probiotic with 37 receiving placebo, alongside a healthy group. The capsule supplied approximately one billion CFU daily for eight weeks.⁴

Bacterial DNA in stool increased with supplementation, but IBS symptoms did not improve significantly more than with placebo. The study was sized around bacterial excretion; symptom relief was secondary. DNA detection did not confirm that the recovered organisms were alive. Procter & Gamble funded the work, and two authors were employees.⁴

A laboratory measure showing exposure cannot, by itself, tell you whether your belly will feel better.⁴

Bring a specific question to the supplement discussion

The US NCCIH describes the evidence as inconclusive. It notes that the 2021 American College of Gastroenterology guideline found insufficient strong evidence to recommend probiotics for IBS. Safety information is also incomplete; reported effects include cramping and nausea, with greater risk in people who are seriously ill or have compromised immunity.⁵

Before a purchase, take a photograph of the strain name, CFU amount and other ingredients. Ask: “Which study matches my symptoms and this preparation, and what change would justify continuing?” Keep pain intensity, bloating intensity and bloating-free days as separate entries rather than one general “gut health” rating.

“Answer Two: Buy Something That Debloats” in Bloated by Dinner examines supplement promises and why evidence for one strain does not transfer to another. Our general probiotic guide covers the wider category.