Cranberry husk and the layer under the husk contain a biologically active substance – antocian. This is a substance produced by the plant itself to protect against such untoward conditions as UV rays, viruses, bacteria and fungi. This substance proves to be useful also for sustaining the health. It is proved, for instance, that antocian prevents bacterium E.coli from attaching to the mucous membrane of the urethra. Thus cranberries or their extract have a favourable effect on the urethral system. Researches have been made of the effect of antocians on viruses and cancer cells. It has been proved that antocians have an antiviral effect and they can diminish the uncontrolled growth of damaged cells or, in other words, cancer cells.