In 1982, it was discovered that the vast majority of stomach ulcers are caused by H. pylori, nasty little bacteria found in the gut. In spite of the evidence, it took the U.S. medical community ten years to accept this finding and change their treatment of ulcers. In 2015, scientists have come to an equally startling conclusion: An imbalance in the bacterial community of your stomach can cause not only ulcers, but also a host of other serious and...