The present invention refers to a preparation for preventing the symptoms of ageing in a human body, and a method for maintaining a correct chronobiological mechanism in the body. The preparation comprises a first dosage unit including soy isoflavones with a genistein content of at least 50% and a second dosage unit including melatonin or a precursor thereof and soy isoflavones with a genistein content of at least 50%, wherein the first and the second dosage units are distinct units to be administered separately from each other.