They are found in yogurts and fermented products such as kombucha (fermented tea), pickles, kimchi (fermented kale) and kefir. Prebiotics refer to non-digestible components that “feed” the probiotics, that is, the “good” bacteria that live in the intestine. They are present in whole grains and foods such as onions, garlic, leeks, bananas, apples, nuts, seeds and legumes.