Gut microbiome and longevity: the 38 trillion organisms that determine how you age

The centenarian microbiome

A 2016 study of Italian centenarians (100–104 years old) and semi-supercentenarians (105–109 years old) found that extreme longevity is associated with a distinct gut microbiome composition characterised by higher levels of Christensenellaceae, Akkermansia, and Bifidobacterium — bacteria associated with reduced inflammation and improved metabolic function. A 2021 Nature Metabolism study of 9,000 individuals found that people with a more unique, individualised microbiome composition (less dominated by common species) had better health outcomes and lower mortality, and that this uniqueness increased with age in healthy individuals but decreased in those with poor health.

The microbiome-inflammation axis

Inflammaging — the chronic, low-grade inflammation that drives most age-related diseases — is substantially regulated by the gut microbiome. A dysbiotic microbiome (one with reduced diversity and overgrowth of pro-inflammatory species) increases intestinal permeability ('leaky gut'), allowing bacterial lipopolysaccharides (LPS) to enter the bloodstream and activate systemic inflammatory pathways. Elevated circulating LPS is associated with accelerated biological aging, increased dementia risk, and higher all-cause mortality.

What damages the microbiome

• Antibiotic use: a single course of broad-spectrum antibiotics can reduce microbiome diversity by 30–50%, with some species taking 6–12 months to recover.
• Ultra-processed food: emulsifiers (carboxymethylcellulose, polysorbate-80) found in processed foods directly damage the mucus layer protecting the gut epithelium.
• Low dietary fibre: the gut microbiome is primarily fuelled by fermentable dietary fibre. Low-fibre diets starve beneficial bacteria and reduce short-chain fatty acid (SCFA) production.
• Chronic stress: the gut-brain axis is bidirectional. Chronic stress alters gut motility and reduces Lactobacillus populations.
• Sedentary lifestyle: exercise independently increases microbiome diversity, particularly Akkermansia muciniphila, independent of diet.

Evidence-based interventions

• 30 different plant foods per week: the American Gut Project found that people eating 30+ different plant foods per week had significantly higher microbiome diversity than those eating fewer than 10. Diversity is the most robust marker of a healthy microbiome.
• Fermented foods daily: a 2021 Stanford RCT found that a high-fermented-food diet (yogurt, kefir, kimchi, kombucha, fermented vegetables) increased microbiome diversity and decreased 19 inflammatory proteins over 10 weeks — more effectively than a high-fibre diet alone.
• Prebiotic fibre: inulin, FOS, and resistant starch selectively feed beneficial bacteria. Sources include garlic, onions, leeks, asparagus, bananas, oats, and cooked-then-cooled potatoes.
• Akkermansia muciniphila: this keystone species, associated with leanness and longevity, is increased by polyphenol-rich foods (pomegranate, cranberry, grape), exercise, and intermittent fasting.