Super Donors

Not every donor works equally well. With the same procedure and the same illness, stool from certain people cures far more patients than stool from others. Doctors call these rare individuals super donors. What sets them apart seems to be an unusually rich, diverse mix of gut bacteria — a fuller toolkit for rebuilding a damaged ecosystem.

Becoming a stool donor is surprisingly hard. Screening is stricter than for blood: candidates are tested for a long list of infections, plus metabolic and even mental-health conditions, since gut microbes appear linked to both. Only a small fraction of would-be donors pass every check. The healthy-looking gut, it turns out, is rarer than it sounds.