Bifidobacterium longum Eases Constipation: Key 2023 Study

clinical-trial PMID: 37992712

Bifidobacterium longum Eases Constipation: Key 2023 Study

Quick Summary: A 2023 study explored how a specific gene cluster in Bifidobacterium longum, a common gut probiotic, helps relieve functional constipation by breaking down arabinan, a type of fiber from plants. In mice and humans, strains with this gene improved bowel movements, but those without it did not, showing that not all probiotics work the same way. This points to smarter choices for gut health.

What the Research Found

Scientists discovered that Bifidobacterium longum needs a special set of genes called the abfA cluster to help with constipation. These genes let the bacteria break down arabinan, a natural sugar found in plant fibers, which then boosts gut movement.

In mice with induced constipation, the full-strength B. longum sped up gut transit by 23% when fed arabinan-rich diets, but a version without the abfA genes had no effect.
In people, taking B. longum with the abfA genes increased bowel movements by 1.8 times per week and made stools softer, thanks to more helpful gut chemicals like acetate and lactate.
The abfA genes were also found in other gut bacteria, and their presence in stool samples predicted constipation with 78% accuracy.
Transplanting human gut bacteria rich in these genes into constipation-prone mice improved their gut speed by 35%, proving the genes play a direct role.

This shows the abfA cluster turns dietary fiber into gut-friendly fuel, easing symptoms of slow bowels.

Study Details

Who was studied: The research included lab mice with induced constipation and 80 adults aged 18-65 who had functional constipation (trouble with regular, comfortable bowel movements). It also used germ-free mice to test human gut transplants.
How long: Mice got treatments daily for short periods to measure quick changes. Human participants took the probiotic for 4 weeks in a controlled trial.
What they took: People swallowed oral capsules with 1 billion live B. longum bacteria per day—either the full abfA version or one missing the genes. Mice got a daily oral dose of the bacteria, paired with arabinan in their diet for best results.

The trial was double-blind and randomized, meaning neither participants nor researchers knew who got the active strain versus the weaker one until the end, to keep results fair.

What This Means For You

If you struggle with constipation, this study suggests picking B. longum probiotics with the abfA gene cluster could make a real difference, especially if you eat fiber-rich foods like fruits, veggies, and whole grains that contain arabinan.

Try it if: You have ongoing constipation from gut imbalance—look for "arabinan-utilizing" strains on labels or ask a doctor for tested options.
Boost results: Pair probiotics with arabinan sources like apples, carrots, or oats to help the bacteria work better.
Personal tip: A stool test for abfA genes might predict if this probiotic fits your gut, leading to personalized relief without trial-and-error.

Overall, it highlights that the right probiotic strain, fueled by diet, can improve daily comfort and regularity.

Study Limitations

While promising, this research has some caveats to consider:
- The human group was small (just 80 people), so results might not apply to everyone, like those with different diets or health issues.
- Diets weren't strictly controlled for fiber in the human trial, which could affect how well the probiotic worked.
- The 4-week test is short— we don't know about long-term benefits or side effects.
- More details are needed on exactly how the abfA genes and their byproducts speed up the gut.

Talk to a healthcare pro before starting probiotics, and wait for bigger studies to confirm these findings for wider use.

Key Findings

The study identifies the abfA gene cluster in Bifidobacterium longum as critical for relieving functional constipation (FC) in mice and humans. Wild-type B. longum improved gastrointestinal transit time in constipated mice by 23% (p<0.01), but this effect was absent in an abfA-deficient mutant strain. Dietary arabinan (a plant polysaccharide) was required for efficacy. In humans, supplementation with abfA-cluster-carrying B. longum increased stool frequency (1.8 times/week, p=0.003) and improved stool consistency (p=0.008) compared to an abfA-deficient strain. The abfA cluster’s abundance in gut microbiota predicted FC diagnosis with 78% accuracy (AUC=0.78). Transplanting abfA-enriched human microbiota into germ-free mice enhanced gut motility by 35% (p=0.02), confirming its functional role.

Study Design

The study combined murine models and a double-blind, randomized, placebo-controlled clinical trial in humans. In mice, FC was induced via loperamide, and effects of B. longum strains (wild-type vs. abfA mutant) were tested. For the clinical trial, 80 adults (18–65 years) with FC were randomized to receive either abfA-cluster-carrying B. longum (n=40) or abfA-deficient strain (n=40) for 4 weeks. Germ-free mice were transplanted with human microbiota to validate abfA-dependent effects.

Dosage & Administration

Human participants received 10⁹ CFU/day of B. longum via oral capsules. Mice were administered 200 μL of probiotic suspension (exact CFU unspecified) daily via oral gavage. Dietary arabinan was controlled in murine experiments but not explicitly quantified in human diets.

Results & Efficacy

Murine model: Wild-type B. longum increased colonic motility by 23% (p<0.01) with arabinan, while the abfA mutant showed no improvement.
Human trial:
Stool frequency increased by 1.8 times/week (p=0.003) in the abfA-cluster group vs. 0.9 times/week in the abfA-deficient group.
Stool consistency improved (p=0.008) in the abfA group, correlating with higher fecal acetate (32% increase, p=0.001) and lactate levels.
AbfA cluster abundance predicted FC with 78% accuracy (AUC=0.78).
Microbiota transplantation to germ-free mice enhanced motility by 35% (p=0.02).

Limitations

Human trial sample size: 80 participants, limiting generalizability.
Dietary control: Human dietary arabinan intake was not standardized, potentially confounding outcomes.
Short duration: 4-week intervention may not capture long-term efficacy or safety.
Mechanistic gaps: How abfA-driven metabolites directly influence gut motility remains unclear.
Translation to humans: Murine findings require validation in larger, diverse human cohorts.

Clinical Relevance

This study underscores that strain-specific genomics (presence of abfA cluster) determine probiotic efficacy for FC. Supplement users should prioritize B. longum strains with arabinan-utilization genes, ideally paired with arabinan-rich diets (e.g., fruits, vegetables). The findings support personalized probiotic therapies based on gut microbiome composition. However, the lack of dietary control in the trial suggests future research should explore synergies between probiotic strains and fiber intake. Clinicians may consider abfA cluster screening to identify FC patients likely to benefit from targeted probiotics.

Source: PubMed (ID: 37992712) | Year: 2023 | Type: Double-blind RCT + murine/microbiota transplant experiments.