In the second half of the 20th century, Russia conducted intensive scientific research on the subject of therapeutic fasting. Doctors studied the viability of this method in the treatment of mental disorders, bronchial asthma, rheumatoid arthritis, hypertension and other diseases. Extensive scientific material has been accumulated, explaining many of the processes that occur in the body during fasting and proving the safety and effectiveness of this method. The obtained results allowed the Ministry of Health to introduce wet and dry fasting as a medical treatment method at state medical institutions under its authority. Dry fasting was less thoroughly studied than wet fasting, so its recommended duration did not exceed 3 days. Barely any studies of longer dry fasting periods were conducted, but several doctors developed this field by working directly with patients. They conducted group fasts autonomously, outside large institutions, and were therefore unable to perform full-fledged experiments. One of these doctors is Sergey Filonov, the author of three books in Russian on dry fasting. His books are not the result of scientific research. They are the notes of a doctor, where the author summarizes his many years of experience and gives recommendations to those readers who want to put his knowledge into practice. In 2018, the revised materials from his books were released in two publications in Italian, and at the end of 2019 – in English (S. Filonov, 20 Questions and Answers about Dry Fasting). One of the features of prolonged dry fasting according to Sergey Filonov is a thorough preparation of the body in advance. The small brochure “Before Dry Fasting” contains a detailed description of cleansing procedures that can be conducted at home, such as intestinal and liver cleansing, recommended by Dr. Filonov prior to fasting, and includes the editor’s remarks on these procedures.