Faecalibacterium prausnitzii

F. prausnitzii is what microbiome researchers call a 'keystone species', its abundance shapes the wider microbial community. It produces butyrate, which colonocytes use as primary fuel. It also produces specific anti-inflammatory metabolites that calm the local immune response. People with healthy gut function tend to have high F. prausnitzii. People with active gut disease tend to have low levels.

• Inflammatory bowel disease (Crohn's especially).
• Repeated antibiotic courses.
• Low fibre, processed-food-heavy diets.
• Heavy alcohol use.
• Stress and chronic short sleep.
• Ageing (gradual decline).
• C-section birth and formula feeding (in infants).

1. Eat 30+ different plant foods per week (the Tim Spector / British Gut Project finding).
2. Resistant starch (cooked-and-cooled potato/rice, slightly green bananas) feeds it especially well.
3. Soluble fibre from oats, kiwi, chia, psyllium.
4. Polyphenol-rich foods (berries, dark chocolate, olive oil).
5. Reduce ultra-processed food. Strongly associated with low F. prau.
6. Avoid unnecessary antibiotic courses; recovery can take 6 months.

Not yet, easily. F. prausnitzii is extremely oxygen-sensitive and dies during processing. It is being developed as a 'next-generation probiotic' but is not yet commercially available in stable form. The realistic path is to feed your existing F. prau through diet rather than try to add more from a bottle.

As a keystone species, F. prausnitzii is less a target than a barometer: guts that stay well-fed with varied plants tend to hold their levels across the decades, and falling levels usually mean the diet or the gut needs attention. Keeping it fed is one of the few microbiome goals that survives every fashion cycle in the field.