Inside the digestive tract lives the gut microbiome, a vast community of bacteria, fungi and other microbes. Each type of microbe needs a different kind of fuel.

Charu Dua puts it simply, “The human gut microbiome, a complex ecosystem of trillions of bacteria, fungi and microorganisms, is heavily reliant on dietary variety.”

When meals repeat too often, the gut misses out on many nutrients. Fibre types change from one plant to another. So do natural compounds like polyphenols. When those are missing, certain beneficial bacteria shrink, while others dominate.

A large public research effort, the American Gut Project, found something striking. People who ate over 30 different plant foods a week had far more diverse gut bacteria than those who ate fewer than 10.

Diversity, in simple terms, means a stronger, more adaptable gut.