The gut microbiome is made up of trillions of microorganisms that help break down food, train the immune system and produce substances that influence many parts of the body. Many people buy probiotic supplements hoping they will improve gut health. Researchers then compared changes in gut bacteria and health symptoms. Professor Sarah Berry said the findings challenge the common belief that probiotics are the best answer for gut health. If you care about gut health, please read studies about how junk food harms your gut health, and how probiotics can protect gut health.