ntestinal microflora is characteristic of each individual. It plays a central role in the metabolic, nutritional, physiological and immune processes of the human body. Disruption of the intestinal microflora can lead to the development of certain diseases. For the prevention and treatment of certain conditions and diseases, the gut microflora can be modulated by diet (dietary fiber) and by the use of probiotics and prebiotics. Probiotics are living microorganisms which, if consumed in an adequate amount, are confirmed to have health effects on the host. Prebiotics are defined as indigestible fibrous portions of food that stimulate the growth and / or activity of certain microorganisms in the gut, thereby improving host health. Probiotics and prebiotics have a positive effect on the composition of the intestinal microflora, providing greater resistance to colonization of pathogenic microorganisms. Dietary fibers are the edible parts of plants or similar carbohydrates resistant to digestion and absorption in the small intestine with complete or partial fermentation in the large intestine. They are divided into soluble and insoluble fibers. Soluble dietary fibers include non-starch polymers which, by virtue of their viscosity and gel-forming ability, prevent the absorption of glucose and fat from the small intestine. Although not digestible, bacterial fermentation occurs in the large intestine. Soluble fibers include pectin, β-glucan, gum, some hemicelluloses and mucus. Insoluble dietary fiber passes through the digestive system almost unchanged. They have the characteristic ability to bind large amounts of water and thus stimulate digestion, increasing the volume of fecal matter. This group includes cellulose, the majority of hemicellulose, and lignin. The recommended daily intake of dietary fiber for men is 38 g and for women 25 g. Dietary fiber is attributed a protective role in the treatment and prevention of certain diseases. In alleviating the symptoms of functional bowel disorders, the fibers show a therapeutic effect, while further research is needed in inflammatory bowel diseases. Higher intakes of soluble dietary fiber have a beneficial effect on reducing the incidence of type 2 diabetes. Higher intakes of fiber, especially whole grains, reduce the risk of myocardial infarction, stroke, and fatal cardiovascular incident. A statistically significant reduction in the risk of colorectal, gastric, breast, and endometrial cancers was observed in individuals with higher fiber intake. Dietary fiber is attributed to a beneficial effect on weight loss and therefore on the treatment of obesity.