To supplement the daily cosmonauts' ration with biologically active substances able to increase adaptability and resistance to the adverse spaceflight factors, an assortment of prophylactic food products to be consumed at specific phases of mission has been developed. Principles of creating dietary compositions, i.e. selection of biologically adequate staples and appropriate use of alimentary supplements with anti-stress, adaptation assisting and antiradiation properties, and search for cooking technologies that will maximally preserve the original qualities of ingredients have been established. Some of these products were tested as components of the MIR rations in 1997-1998.