THE MICROBIOME
Why your gut runs more
than your digestion
By the numbers, you are at least as much microbe as human. The cells in and on your body are split almost evenly between microbial and human — close to a one-to-one ratio, not the ten-to-one figure you may have read, which the science corrected in 2016. But look at genes rather than cells and it isn’t close at all: your microbes carry more than ten million genes, against roughly twenty thousand of your own. By that measure you are overwhelmingly more microbial than human. This community, most of it living in your gut, does work your body cannot do alone. When it’s healthy, you rarely notice it. When it isn’t, you notice almost everything.
~1.3 : 1 microbial to human cells · 10M+ microbial genes (vs ~20,000 human) · ~90% of the body’s serotonin made in the gut · ~70% of immune tissue in the gut
Digestion and metabolites. Your gut microbes break down fibres your own body can't, turning them into compounds it can use — including short-chain fatty acids, which nourish your gut lining. In fact, a large share of the small molecules circulating in your body are shaped by the microbiome in some way — around 71% of those measured, in one major study. What you feed it, it turns into what feeds you.
Immunity. By common estimates, around 70% of the body’s immune tissue is concentrated in and around the gut wall — the gut-associated lymphoid tissue (GALT) — in constant conversation with the microbes on the other side. A balanced microbiome helps that system stay calibrated.
The gut–brain connection. Around 90% of the body’s serotonin is produced not in the brain but in the gut — by specialised enterochromaffin cells in the gut lining, with gut microbes helping regulate how much is made. It’s one of the clearest illustrations of why “gut feeling” isn’t just a figure of speech.
What the gut microbiome
actually does
LONGEVITY
The gut and how we age
“Longevity” gets used loosely. The more useful idea is healthspan — not how long you live, but how many of those years you spend well. A growing body of research places the gut close to the centre of it.
The link is the machinery described above, read over a longer horizon. As we age, the microbiome tends to lose diversity and low-grade inflammation tends to rise — a drift researchers have nicknamed “inflammaging.” Because gut microbes help regulate inflammation, train the immune system, and produce or suppress compounds that circulate through the body, the state of that community is one of the factors that shapes how the body holds up over time.
One example is TMAO, a compound produced by gut microbes that research has associated with cardiometabolic risk. How much of it your gut produces depends partly on which microbes are present and what they are fed — precisely the kind of thing a fibre-rich, fermented, plant-based diet can influence.
None of this is a promise of extra years, and no single food delivers them. The honest takeaway is simpler, and stronger: the gut is one of the most modifiable systems we have, and the choices that support it — fibre, fermentation, a diversity of plants — are among the most accessible levers for ageing well.
Why modern guts are under
pressure
The diversity that keeps a microbiome resilient is being eroded. Industrialised diets have narrowed what we eat — a striking share of the world's food (by one widely cited estimate, around three-quarters) now comes from just 12 crops — while antibiotics, ultra-processed food, and modern living reduce the microbial community further. Studies of populations still eating traditional, high-fibre diets show gut diversity that industrialised guts have largely lost.
Where millet comes in
Millets are among the oldest cultivated grains, domesticated more than ten thousand years ago, and they are rich in exactly the kind of fibre a microbiome thrives on. Fermenting millets — as mi-biotics™ does — makes their nutrients more bio-available. Adding live cultures to that makes the product rich in prebiotics, probiotics, and postbiotics. It’s an ancient food, asked to do a modern job.