You Can’t Beat a Bit of Sensationalism
Having read the headlines about the concept of super poo donors - people whose poo transfusions are more likely to cure various gut issues such as Clostridium difficile, ulcerative colitis and crohns when donated to sufferers, I had started to amuse myself with what I might put on my business card. Super Pooper? Stool Mule? The Empress of Excretion?
Then I read the scientific paper (and some of the studies) to which this headline refers. And I am sorry to say that I will not be printing my super pooper business cards any time soon, because we really don’t yet know that super pooper donors are actually a thing. And (although I can’t quite bring myself to acknowledge this), even if they are, I might not be one!
This is what the paper that generated the headline actually said:
We don’t yet know what comprises a healthy gut microbiome from an inventory standpoint. We can’t compile a shopping list of must-have microbes that is applicable to all.
But we do currently believe that having a stable and diverse gut microbe community correlates with a healthy intestinal state.
In the main, we haven’t yet reliably shown that upsets to our gut microbes CAUSE disease. We have shown association - that the two go together – but not that the microbial upset is the culprit per se. We may well show causation in the future, but we haven’t done so yet. It is a very complicated world in there!
Fecal microbial transplantation (FMT) is a therapy that has been around since the 4th century (records from China) but despite this, we still know very little about how it actually works. It is a kind of pooey bacterial transfusion from a healthy donor to an ailing one, which seeks to reset the recipient’s gut microbiota to a healthier state and in so doing, improve various health issues.
The success of FMT is measured by improved clinical markers (reduced diarrhoea or reduced inflammatory markers, for example), but also a shift of microbial profile towards that of the donor.
The idea of super pooper donors started from a study of just 75 patients with ulcerative colitis. 9 of them were put into modest clinical remission by FMT and 7 of those 9 people had had poo from the same donor. There have been other small studies but currently, we can’t predict the clinical success of a donor in advance. The interaction is just too complicated.
Choosing an appropriate FMT donor does appear to be one of the key factors in successful FMTs though, which is why the process involves extensive screening. The gut microbial diversity of the donor is one reliable factor that helps us try to predict transplant success. As is the presence of what we think of as “keystone species” - species that have a disproportionally large influence for the better if present in our gut community. But it is not just about the microbial qualities of the donor in isolation.
The recipients’ microbial community affects FMT outcome too. Microbial interactions matter. Donor-recipient compatibility is a thing. So is the recipient’s genetics and their immune function. Their diet is a factor too, along with subsequent antibiotic use and we are only just starting to look at these influences in relation to FMT treatments.
Tiny study sizes, lack of methodological continuity and differences between treating Clostridium difficile (where the issue is an overgrowth of one type of bacteria) as opposed to treating ulcerative colitis or crohn’s disease, (where a complex interplay of microbes, environment, genetics and immune function is involved), means we don’t have enough evidence yet as to what is going on in FMT. FMT outcomes have been much more modest and variable in treating ulcerative colitis and crohn’s compared to Clostridium difficile infections.
BUT, what limited studies there are, suggest that a bacterially rich donor does not necessarily guarantee FMT success. Bacterial strains from a donor are more likely to move in to the recipient if the recipient already has some of the same species as the strains being introduced (strain being a subgroup of species).
The fact is, one stool does not fit all - we need to be able to match donor to recipient more accurately than we can at present. It is true that some donors may “fit” more recipients than others, but it is such early days, we just can’t be sure. And FMT appears to work better with some illnesses compared to others.
Most interestingly to me though, someone has done a tiny study of 5 people with recurrent Clostridium difficile infection and given them stool solution with no bacteria in it (but which did contain bacterial debris, proteins, DNA, metabolites, anti-microbial compounds and viruses). All 5 patients achieved resolution from their Clostridium difficile infection and remained symptom-free for the duration of the study (6 months). Is it the bacteria? Is it their metabolites? Or something else entirely?
FMT treatment is a very exciting development in supporting, repairing and better understanding our gut health. We are really only just beginning to appreciate just how many pieces there are in this particular jigsaw puzzle. Whilst we do know the donor is influential to FMT success, the idea of super pooper donors is not yet supported by quality evidence. But hey, it makes a good headline!!