Luxembourg Institute of Health

And then there are fiber's effects on gut microbes, which digest that fiber for food.

"Fiber is actually one of the ingredients in our diet which has perhaps the biggest impact on the microbiota," says Mahesh Desai, a microbiologist at the Luxembourg Institute of Health.

Research in turn has started to explain how those gut microbes influence our health.

A key effect is what those microbes do to affect inflammation, which is a known contributor to diseases such as colon cancer, heart disease, and diabetes.