Background: The human gastrointestinal tract harbors hundreds of millions of microorganisms, which create a unique environment for each individual. The relationship between gut microflora and human health is being increasingly recognized, and the influence of gut microbiota on the host is well characterized, including maintenance of the body's energy metabolism and immune system. Gut microbiota have been found to be closely linked to obesity, allergy, diabetes, cancer or even some mental diseases. Diet can strongly affect human health, partly b...