Dietary fiber is a non-digestible carbohydrate that belongs to the group of polysaccharides. In plants and animals, they may have different biological functions. Dietary fibers are divided into soluble (pectins, beta-glucans, gums and mucus) and insoluble (cellulose, hemicellulose and lingin). The average daily intake of fiber should be 25 to 35 grams of fiber per day and preferably a mixture of soluble and insoluble dietary fiber. Dietary fiber is rich in cereals (oatmeal, buckwheat), fruits (blackberries, avocados), vegetables (beetroot, chickpeas), nuts (almonds, chestnuts), and the amount and type of dietary fiber varies from food to food. Insoluble fibers increase the volume and frequency of digestion and shorten the passage time through the digestive tract, while soluble fibers such as pectin do not significantly alter the process within the digestive tract or shorten the passage time of the faeces and the gut microflora completely decompose them. Nutrition rich in dietary fiber from whole grains, fruits and vegetables has positive effects on human health as their consumption reduces the incidence of multiple types of cancer. Due to all of the above, foods rich in dietary fiber are also functional foods and should therefore be introduced into the diet.