We cannot digest all the fiber we eat.
But some of the microorganisms living in our gut can.
Certain types of dietary fiber reach the large intestine largely undigested. There, gut microorganisms can ferment them and use them as a source of energy.
This process produces substances called short-chain fatty acids, including butyrate, acetate and propionate.
These compounds have several biological functions. They help support the cells lining the colon and are involved in communication between the gut microbiome and the rest of the body.
This is one reason fiber can influence health beyond digestion.
But not all fiber behaves in the same way.
Different fibers are used by different microorganisms. Some fibers have well-established prebiotic effects, meaning they are selectively used by microorganisms in ways that can benefit health.
This is also why eating one supposedly “perfect” source of fiber is unlikely to be the best strategy.
Vegetables, fruits, legumes, whole grains, nuts and seeds contain different combinations of fibers and other plant compounds.
A varied plant-based food intake therefore provides the gut microbiome with a wider range of substrates.
Fiber supplements can be useful in selected situations. But they do not reproduce the full nutritional complexity of eating a variety of whole plant foods.
For everyday health, diversity matters.
