The invention relates to a method for preparing alkali and heat stable polyols, whereby sugar alcohols are treated with reagents to obtain stabilized sugar alcohol syrups and the stabilized alcohol syrup is subjected to a purification step by passing the stabilized sugar alcohol syrup over at least one ion-exchanger resin, and the stabilized sugar alcohol syrup being purified by a double passage over a cationic anionic ion-exchanger configuration (CACA), comprising at least a first weak acidic cationic ion-exchanger resin and a second strong, medium or weak basic anionic ion-exchanger resin.