Subject of the invention is a process of manufacturing a selenium containing composition from selenium containing plant seeds comprising the step of extracting seeds of selenium containing plants with an apolar organic solvent yielding an extract wherein the selenium containing plants are selected from the group consisting of Lecythis ollaria Loeffling, Lecythis minor Jacquin, Lecythis usitata Miers, and Lecythis tuyrana Pittier, collecting the extract and substantially removing the apolar organic solvent yielding an oily phase having an insoluble residue, isolating the oily phase and the insoluble residue. Subject to the invention are further a method of cold pressing selenium containing plant seeds, selenium containing compositions and nutritional supplements.