Embodiments of a method and supplement for preventing and/or treating gastrointestinal distress, including ulcer conditions, in animals such as humans are disclosed. The supplement is in a tablet or capsule form and comprises mastic gum and an emulsifying agent such as lecithin. The supplement may also comprise B vitamins, one or more prebiotics or probiotics, and one or more minerals as well as, pH buffers and flavoring. A disclosed method of preventing and/or treating gastrointestinal distress comprises orally dosing an animal such as a human with the supplement at least once daily.