Since the gut microbiome was sequenced and published in 2010, intensive biomedical research has highlighted the key role of microbiota in human health. The gut microbiota extends its action from the colon to other organs and tissues, including the brain. The microbiota catabolizes indigestible diet components to produce metabolites that affect gene expression and that may have beneficial or detrimental effects on immune function, intestinal inflammation, metabolic syndrome and neurological functions. This seminar focuses on the mechanisms of action and the effects of the gut microbiota in the prevention of colon cancer, the second cause of cancer death worldwide. Special attention will be paid to the interactions of the microbiota with non-digestible carbohydrates and antioxidants, which are the two main diet components affecting the composition and function of the microbiota, and its potential health effects. The main risk factors in the modulation of intestinal microbiota associated with inappropriate eating habits will also be discussed. The speakers will present their most recent research results on these topics.