'Cultured': A Look At How Foods Can Help The Microbes Inside Us Thrive

Katherine Harmon Courage wants us to think about digestion as a collaborative journey between us and our microbes. In her new book, Cultured: How Ancient Foods Can Feed Our Microbiome, she envisions digestion not as a simple food-in, excrement-out process, but as a series of encounters with varying microbial players that takes place along the winding 30-foot tunnel of our gastrointestinal tract. Along the way, microbes digest the food we can't, and in return we give them a warm, well-stocked place to live.

But a surge in microbiome research over the past two decades has revealed they do much more than simply digest food. They can mediate weight gain, fight off infection, and even alter our mood. Scientists still have much to learn about the identity of these microbes, which are important, and how the beneficial ones work their magic.

Incomplete understanding hasn't stopped the burgeoning probiotic industry, which argues that we can improve our gut health by taking a pill stuffed with billions of beneficial strains of bacteria,