Our gut protects us from toxins, viruses and bad bacteria. Lots of bacteria live in our gut. We have them from the time we are born. They can be good or bad. The good ones help you digest foods. They also make substances that keep us happy and calm. They make B vitamins that we need for our nervous system. The bad ones, on the other hand, cause digestive problems. They can give us diarrhea or worse. Some experts think that the bad ones cause many diseases. As we get older, we often have more bad bacteria than is healthy. [...]