Encouraging the health of your existing gut microbiome (gut bacteria), then cultivating an environment for diversity of that gut microbiome and finally daily weeding and feeding is the way to an awesome digestive system and then a rock solid immune system.
It's time the big food companies that have addicted us to the processed sugar in our food and drinks, were held accountable. By systematically addicting us to their products, with the help of our governments, it is us paying the heaviest price.