One and a half kilograms. That's how much the bacteria in your gut weigh. We're talking about 10¹³–10¹⁴ microbial cells and roughly 600,000 genes — 20 times more than in your own genome. This "invisible ecosystem" influences digestion, immunity, metabolism, mood, and even response to cancer therapy.
In 2025, a major group of Chinese experts published an updated consensus on the clinical use of microecological modulators — probiotics, prebiotics, and fecal microbiota transplantation (FMT). The document covers 17 disease categories and cites 227 scientific references.
Let's break down the key findings.
Three Degrees of Dysbiosis
The consensus identifies three levels of microbiome disruption:
- Latent — bacterial composition is already altered, but there are no symptoms. The body compensates.
- Local — gut symptoms appear: bloating, irregular stools, discomfort.
- Severe — dysbiosis extends beyond the gut and affects other organs and systems.
It's this third level that explains why microbiome disruption is linked to liver disease, brain disorders, and even cancer.
The Gut: When the Microbiome Breaks Down
The gastrointestinal tract is the microbiome's "home territory," and it's where disruptions manifest most clearly.
Irritable Bowel Syndrome (IBS)
IBS is one of the most common functional GI disorders. The 2025 consensus confirms: microbial therapy works, but the approach depends on the subtype.
- IBS-D (diarrhea-predominant) — probiotics at 10⁷–10¹⁰ CFU reduce frequency and severity of diarrhea
- IBS-C (constipation-predominant) — specific strains improve transit and stool consistency
- IBS-M (mixed) — combination protocols
- IBS-U (unclassified) — individualized selection
The key message: there is no "one probiotic for IBS." Strain, dose, and duration are matched to the specific subtype.
Inflammatory Bowel Disease (IBD)
Ulcerative colitis and Crohn's disease are chronic inflammatory conditions where the microbiome plays a central role.
A striking finding from the consensus: the probiotic mixture VSL#3 in maintenance therapy for ulcerative colitis is comparable in efficacy to mesalazine (5-ASA) — the standard first-line medication. This doesn't mean probiotics replace drugs. It means they can be a legitimate part of the treatment regimen.
In Crohn's disease, dual combinations (probiotic + prebiotic) enhance the therapeutic effect.
C. difficile Infection
Clostridioides difficile is the gut's primary "enemy" after antibiotics. According to the consensus, 25–30% of all antibiotic-associated diarrhea (AAD) cases are caused by this bacterium. FMT has been included in American and European guidelines as the gold standard for recurrent CDI treatment since 2013.
Antibiotic-Associated Diarrhea (AAD)
Between 5 and 39% of patients on antibiotics experience diarrhea. The consensus recommends prophylaxis with high-dose probiotics (≥5×10⁹ CFU/day), started within the first 2 days of antibiotic therapy. Functional GI disorders are also highlighted as an area where probiotics show consistent benefits.
Liver and Metabolism
The gut-liver axis is one of the most actively studied mechanisms. Gut bacteria affect the liver via the portal vein, and impaired gut barrier function leads to endotoxemia — bacterial toxins entering the bloodstream.
MAFLD (Metabolic-Associated Fatty Liver Disease)
Metabolic liver diseases are a modern-day epidemic. The consensus presents data showing that the probiotic mixture VSL#3 over 3 months reduces liver enzyme levels (transaminases) and TNF-α — an inflammation marker. Improved insulin resistance is also noted separately.
Liver Cirrhosis
In cirrhosis, the gut-liver-brain axis breaks down. Bacterial toxins from the gut that the liver can no longer neutralize reach the brain, causing hepatic encephalopathy — confusion, memory problems, and behavioral changes. Probiotics help break this vicious cycle.
Obesity and Metabolic Syndrome
Metabolic syndrome is a cluster of conditions including obesity, hypertension, dyslipidemia, and insulin resistance. The consensus highlights Akkermansia muciniphila as a next-generation probiotic (NGP): it improves insulin resistance, reduces body fat percentage, and normalizes gut barrier function.
Beyond Akkermansia, next-generation probiotics include Faecalibacterium prausnitzii and Bacteroides species. These aren't the classic yogurt lactobacilli — they're representatives of the normal anaerobic gut flora.
Type 2 Diabetes
Microbial therapy for type 2 diabetes shows reductions in HbA1c (glycated hemoglobin) and improvement in the HOMA-IR index — the primary measure of insulin resistance. This is an additional tool alongside standard glucose-lowering therapy.
Brain and Mind: The Microbiome-Gut-Brain Axis
The gut-brain connection isn't a metaphor. The vagus nerve, neurotransmitters, short-chain fatty acids — these are real communication channels between the microbiome and the central nervous system.
Depression
In depression, studies show that the combination of Lactobacillus helveticus R0052 + Bifidobacterium longum R0175 at 3×10⁹ CFU/day for 8 weeks increases BDNF (brain-derived neurotrophic factor) — a protein critical for neuroplasticity. This doesn't replace antidepressants, but it can be part of a comprehensive approach.
Autism Spectrum Disorders
About 50% of children with autism have GI problems — this isn't coincidence, but a manifestation of shared gut-brain axis disruption. The strain Lactobacillus plantarum PS128 improves behavioral outcomes in children with autism. The consensus emphasizes: correcting GI symptoms can positively influence core autism manifestations.
Schizophrenia and Bipolar Disorder
The data is still preliminary but encouraging. Bifidobacterium breve A-1 and prebiotics that boost butyrate production (a short-chain fatty acid with anti-inflammatory properties) showed improvement in patients with schizophrenia. In bipolar disorder — reduced rates of rehospitalization.
The Microbiome in Cancer Treatment
Perhaps the most unexpected section of the consensus for non-specialists. The microbiome doesn't just "exist alongside" the tumor — it actively influences the body's response to treatment.
Liver Cancer and Colorectal Cancer
In oncological conditions, probiotics find application in the perioperative period. Bifidobacterium longum accelerates recovery after liver surgery. In colorectal cancer, probiotics reduce chemotherapy side effects and improve postoperative recovery.
Immunotherapy: A Breakthrough Involving FMT
The hottest topic in oncology is checkpoint inhibitor (ICI) immunotherapy, such as anti-PD-1. The problem: 60–70% of patients don't respond to it. And this is where the microbiome enters the picture.
A study by Kim et al. (2024) demonstrated that FMT combined with anti-PD-1 therapy can overcome resistance in solid tumors. The mechanism: certain gut bacteria stimulate immune cells that then attack the tumor more effectively.
In non-small cell lung cancer (NSCLC), adding probiotics to immunotherapy increases both overall and progression-free survival. Microbiome "signatures" — specific bacterial combinations — are being evaluated as predictors of immunotherapy response. This means: microbiome analysis could help determine in advance who will benefit from immunotherapy and who won't.
FMT: From a Single Indication to Dozens
Section 17 of the consensus is devoted to fecal microbiota transplantation — and its scope is impressive.
From C. difficile to Systemic Therapy
FMT began its journey as a treatment for recurrent C. difficile infection. Today, the consensus describes its use in IBD, IBS, obesity, diabetes, autism, depression, and even oncology. This isn't an "experimental procedure" — it's a field with a growing evidence base.
Delivery Methods
FMT technology has evolved: from nasogastric tubes and colonoscopy to capsules. SER-109 — the first capsule-based FMT product manufactured to GMP standards — has already been approved for clinical use. Learn more about the FMT method and delivery approaches.
The Future: Synthetic Microbial Communities
SMT (synthetic microbiota transplantation) is the next step. Instead of transplanting an entire ecosystem, scientists create specific bacterial combinations tailored to a specific condition. It's like moving from whole blood transfusion to targeted therapy with individual components.
Think of it this way: FMT is organ transplantation, except instead of an organ, it's an entire ecosystem. And SMT is when you know exactly which "inhabitants" the ecosystem needs and introduce precisely those.
What This Means for You
The 2025 consensus isn't an abstract scientific document. It confirms three things that matter for every patient:
- The microbiome isn't a trendy topic — it's clinical reality. 17 disease categories, 227 references, dozens of experts — this is an evidence level that can't be ignored.
- Probiotics work, but not all the same way. Strain, dose, duration, and even disease subtype determine the outcome. "Taking some lactobacilli" is not a strategy.
- FMT is one of the most promising tools. From C. difficile to cancer immunotherapy — the range of applications expands every year.
If you're interested in how microbial therapy might help in your specific case — contact us for a personalized consultation.
Source: Chinese Expert Consensus on the Clinical Application of Microecological Modulators (2025 Edition). 227 bibliographic references.
