Microbiome basics

The Living Ecosystem That Shares Your Body

The human body was long described as outnumbered ten to one by its own microbes. That figure turned out to be wrong.

A 2016 recalculation put the real ratio at closer to 1.3 to 1, still in the microbes' favour, but nowhere near the dramatic gap once assumed.

That correction changed a number, not the underlying picture. An enormous, living community of microbes still calls the human body home, and it does real, measurable work there.

Why this ecosystem matters, and where to start

Most of these microbes live in the gut, mainly the large intestine, where oxygen is scarce and conditions favour bacteria that thrive without it. Together they weigh about 200 grams, roughly the same as a small orange.

This isn't one organism. It's an ecosystem of thousands of different species, interacting with each other and with the body in ways scientists are still mapping. Some produce compounds that calm inflammation. Others help extract energy from food the body can't digest on its own. Some communicate with the brain.

The pages in this section build up the basic picture piece by piece: what the microbiome actually is, what lives there beyond bacteria, what these microbes need to stay healthy, what damages them, and what their daily output can reveal about how well the whole system is working.

Source: Revised Estimates for the Number of Human and Bacteria Cells in the Body

No two people carry quite the same version of it

Even close family members living in the same household carry meaningfully different gut bacterial communities from one another. Diet, birth history, medication use, and countless small daily exposures all leave their own mark.

This is why the same food, the same probiotic, or the same course of antibiotics can affect two different people quite differently. They aren't starting from the same underlying ecosystem.

It also means there's no single, universal fix. What consistently helps across almost everyone studied is variety, feeding a broad range of plant fibres and compounds rather than relying on any single ingredient to do the work alone.

Source: Human gut microbiome: the second genome of human body

What this means for you

None of this requires a medical background to understand or act on. The same basic principle runs through all of it: this is a living community that needs feeding, and what reaches it through diet shapes how well it can do its job. A varied, plant-rich diet gives this ecosystem the broadest possible range of fuel to work with. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.

Explore microbiome basics on this page

Use the panels on this page to learn what the microbiome actually is, what other organisms share space with its bacteria, and how diet, damage, and daily habits all shape it.