Celt Naturals. Sterol117 is a patented and clinically tested supplement that modulates the immune system by “up-regulating” it when it is under-performing and “ down regulating” it when it is over performing. Plant sterols, which are not always readily absorbed by the body, are enteric coated for protection against acids found in the stomach. The ingredients are then delivered to the lower bowel, where they are released in tact to assist the body in the healing process. Our phytosterols are only extracted from non – GMO, soy beans.