BREAKING 🧵
A gut bacterium is showing up — or rather disappearing — across all three phases of COVID-19.
Severely ill patients have less of it.
Recovered patients get it back.
Long COVID patients don't.
Its name is Faecalibacterium prausnitzii. And what it does explains a lot. 👇
F. prausnitzii is one of the most abundant bacteria in a healthy human gut.
It produces butyrate — a molecule that:
• Fuels your colon lining
• Seals your gut barrier
• Suppresses inflammatory signals
• Regulates your immune system
When it disappears, all of that fails at once.
Severe COVID-19
A 2025 meta-analysis pooling data across 10 independent studies confirmed:
F. prausnitzii depletion: logFC = -1.24 (95% CI -1.68 to -0.80)
Translation: It was significantly lower in every severe COVID cohort analyzed.
The more depleted. The sicker the patient.
Recovery
Patients who fully recovered from COVID-19 showed normalization of their gut microbiome — including return of F. prausnitzii — within approximately 6 months.
Butyrate-producing bacteria were among the first to come back.
The gut was healing. The bacteria were the signal.
Long COVID
Liu et al. 2022 (Gut journal) tracked 106 Long COVID patients over 6 months.
F. prausnitzii and Bifidobacterium pseudocatenulatum showed the STRONGEST inverse correlation with Long COVID development of any bacteria studied.
Less of them at baseline = more likely to have persistent symptoms.
Why does this matter beyond the gut?
↓ F. prausnitzii → ↓ butyrate → gut barrier breaks down
→ inflammatory signals enter bloodstream
→ cross into the brain
→ microglial activation
→ brain fog, memory problems, fatigue
This is the same gut-brain pathway seen in Parkinson's and Alzheimer's disease.
Long COVID may be hijacking the same route.
A randomized controlled trial just tested this.
463 Long COVID patients. Synbiotic targeting gut bacteria (SIM01) vs placebo. 6 months.
Results (Lancet Infectious Diseases 2024):
Difficulty concentrating: 62% vs 39% alleviated ✓
Memory loss: 42% vs 27% ✓
Fatigue: 63% vs 43% ✓
Pulmonary symptoms: no significant difference.
The gut fixed the brain symptoms. Not the lungs. That tells us something.
What we do NOT yet know:
• Whether F. prausnitzii depletion causes Long COVID — or is caused by it — or both
• The SIM01 trial used vitamin C as placebo, not inert starch
• Results need independent replication
• Direct F. prausnitzii supplement does not exist yet
Association is strong. Causation is unproven. That's where the science actually is.
No F. prausnitzii supplement exists yet. But you can feed it.
It thrives on fermentable fibre:
✓ Jerusalem artichoke
✓ Chicory root
✓ Leeks, asparagus, onion
✓ Resistant starch (underripe banana, cooled rice)
✓ Mediterranean diet pattern overall
NOTE: Probiotics carry real risks for immunocompromised individuals and the elderly. Always consult your doctor.
This is part of a disease series on Faecalibacterium prausnitzii — one gut bacterium found depleted across Parkinson's, Alzheimer's, MS, IBD, diabetes, cancer, and now Long COVID.
Parkinson’s
x.com/Neuroscope_mp/…
Alzheimer’s x.com/Neuroscope_mp/…
Aging x.com/Neuroscope_mp/…
Full referenced deep-dive on coming soon
Follow @Neuroscope_mp so you don't miss the next thread.
#LongCOVID #Microbiome #GutBrainAxis #Neuroscience
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