About Us a Gentle Earth Retreat Center is run by Katherine Croll, CNC, an experienced juice faster, biologist, yoga teacher and cutting edge nutritionist (and our founder) and her husband Jeff Coleman. Katherine and Jeff have conducted countless juice fasts, yoga and nutritional programs. Katherine is also a sought after lecturer, writer,medical researcher and nutritionist. They have worked with both healthy individuals who wish to maximize their health as well as individuals with a wide variety of health problems. Gentle Earth Retreats (also known by its Spanish name in Costa Rica, "Mundo Tranquillo Retreats", has been offering juice fasting and nutritional programs and education for over ten years. Our center in Costa Rica is welcome new addition.