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I first heard about faecal transplants while listening to one of Mark Crislip’s podcasts (based on one of his posts at Science-Based Medicine. I always find his work informative & entertaining, though his sarcasm may not be to everyone’s taste). With the title ‘The species in the faeces’ I knew I was going to hear something to do with, well, poo… (You might not want to read what follows while eating lunch.)

Our bodies are home to an enormous number and variety of bacteria, both outside and within. That includes perhaps tens of thousands of species inhabiting the human gut – and contributing more than 50% (by mass) of the end product of that part of our anatomy. Far from being undesirable fellow-travellers, many of the members of those bacterial communities (for each part of the gut has its own assemblage of species) play important roles in things such as our susceptibility to disease. And throwing them out of balance can affect our health quite markedly – for example, antibiotic treatments can have (as a side effect) quite a negative impact on gut function, and one that can last for considerable periods of time. (Crislip remarks that if we were coprophagic, like rabbits, this would be less of a problem, as the normal gut flora would repopulate quite quickly…)

Anyway, while antibiotics can cause diarrhoea in some patients, another (non-food poisoning) cause is an overgrowth of a bacterium called Clostridium difficile. As an infectious-disease physician, Dr Crislip has a strong interest in any potential means of treating this one, as apparently it’s difficult to clear with antibiotics (which of course may well have their own side effects) & has a high relapse rate. In his post, while he was rightly scathing about the various other claims made for faecal transplants, he noted that this particular treatment did have a good ‘cure’ rate for C.difficile infection.

And this week, on Facebook one of the science pages I follow linked to a report of the results of a clinical trial of faecal transplants, in which they performed considerably better than the more conventional antibiotic treatments. They might want to look at alternative delivery routes, though; somehow I find the idea of delivery via a nasogastric tube (or more accurately a naso-ileac tube) a little hard to stomach. (Is the use of synthetic poo likely to overcome this aversion? Not sure.)

Quite apart from the ick factor, there issues that warrant further investigation. Each of us has their own particular assemblage of gut bacteria (& viruses, & protozoa), & Crislip notes that you’d probably get optimum results from a faecal transplant if the donor’s, er, ‘product’ was as close as possible in gut flora to the recipient’s healthy norm. He cautions that use of random donors could have the potential to generate other upsets as the recipient’s immune system reacted to the new lot of bugs.

You can, of course, find all sorts of claims on the internet relating to supposed health benefits of this, that & the other. And so it is for faecal transplants. Faecal transplants as a cure for depression & MS? Frankly, that sounds like a lot of, well, steaming brown stuff.