Rasayanas support the prevention of of illnesses and helps to minimize the consequences of diseases that might already have set in. This is true not only in regard to the physical but also to the psychic situation.
Especially the primeval defending energy in the body (Ojas) is nurtured by the rasayanas. Most known Rasayana is Chyavanprash, which is prepared from Amla fruits and 50 different herbs. The great Indian sage Chyavan of antiquity is supposed to have regained his youthful energy by regularly taking this rasayana.