Your gut bacteria is an expression of the foods that you consume on a daily basis.

One thing that stuck out to me was when he talked about the relationship between people and their environment. How health is not in a vacuum, but in constant negotiation and collaboration with the world around you. He uses this to suggest fermenting things yourself, to engage in this process with the microbes in your environment. It's easy and fun!

Here's a 6 minute video where Katz talks about fermentation, and walks you through a basic process, in a beautiful and rustic kitchen I still dream about getting to cook in: https://www.youtube.com/watch?v=i77hU3zR-fQ

Avoid alcohol, sugar, and processed foods. These things increase bad gut bacteria and decrease the good ones.