The gut microbiome, explained

You are host to trillions of microorganisms, and, far from passengers, they help digest your food, train your immune system, and even talk to your brain.

Inside every human gut lives a vast, invisible ecosystem. It is tempting to think of it as separate from us. In truth, it is part of how we function.

The scale of it

The human gut is home to as many as 100 trillion microorganisms, carrying collectively around 150 times as many genes as the human genome, across more than 3,000 bacterial species.¹ It is one of the most densely populated ecosystems on Earth, and it is inside you.

What it does for us

These microbes earn their keep. They ferment food our own enzymes cannot break down, synthesise certain vitamins, and produce short-chain fatty acids that nourish the gut lining. They help regulate the intestinal barrier and the immune system, and they crowd out invading pathogens.¹²

Not passengers, but partners, in digestion, immunity, and more.

A conversation with the whole body

The microbiome's influence reaches well beyond the gut. Its balance has been correlated with obesity, heart disease, inflammatory bowel disease, and certain cancers, and it even participates in the development of the nervous system, one strand of the much-discussed “gut–brain” connection.²

Why it matters

Understanding that health is, in part, an ecological question, a matter of tending a living community rather than simply feeding a body, is reshaping how we think about nutrition, immunity, and disease.