Some of the best fermented foods for gut health include live cultures found in not only yogurt and a yogurt-like drink called kefir, but also in Korean pickled vegetables called kimchi, sauerkraut, and in some pickles. The jars of pickles you can buy off the shelf at the supermarket are sometimes pickled using vinegar and not the natural fermentation process using live organisms, which means they don't contain probiotics. To ensure the fermented foods you choose do contain probiotics, look for the words "naturally fermented" on the label, and when you open the jar look for telltale bubbles in the liquid, which signal that live organisms are inside the jar.