One hurdle to fulfilling this potential is that it can be hard to predict the effects of donor stool on a recipient’s microbiome. Studies have suggested that there may be super donors, for instance, whose poop is much more likely to succeed at treating C. diff infections than average. Other researchers, including the authors of this paper, argue that we might get clearer benefits from banking a person’s healthy stool at a young age and then transplanting it at a later date when they become sick with a relevant health problem.

The proposal comes from researchers at Harvard Medical School and Brigham and Women’s Hospital (BWH) and is laid out in a paper published Thursday in Trends in Molecular Medicine.

This concept is known as an autologous transplant, and it’s already used in other areas of medicine. People with cancers of the blood can donate some of their immune-related stem cells before they undergo chemotherapy; afterward, the cells are given back to help heal the bone marrow damaged by these treatments. Another example involves stem cells gathered from umbilical cord blood, which can be stored in case the child develops certain health problems.