Supports the Stomach and Duodenum Dietary SupplementMastic Gum 500 contains natural tree stem mastic gum (Pistacia lentiscus) from a shrub-like tree grown mainly in Greece and Turkey. Mostly composed of resinous gum and volatile oils, mastic has been used for centuries by traditional healers for stomach distress. Mastic Gum supports gastric and duodenal cells and tissues.