Fecal transplants for sports performance are in the news again (this was one of those topics that has been talked about as a future possibility, but not actually tested in the field, for a while). Google 'poop doping' and 'cycling' for links. In this case, an amateur competitive cyclist got a fecal transplant from a high level competitor. Afterwards, she saw her training improve, greatly improved her recovery, and saw general improvements in her health.
At the same time, you can find articles in places like gizmodo telling you that no, fecal transplants won't make you a better athlete, because the people who write for gizmodo don't understand the difference between absence of evidence and evidence of absence.
The theory: What's this all about?
Your intestines are full of bacteria. That is why it's important to wash your hands after using the bathroom. Not just one strain of bacteria, either - everybody has a lot of different strains, in different proportions, living in their intestines. These bacteria help break down certain foods, produce chemicals that can get into your bloodstream and affect your health (butyric acid, branched chain amino acids. lots of others), and seem to impact your health in lots of other ways that are somewhat mysterious (impact insulin resistance, affect mood, influence the immune system, impact bodyfat levels, and so on).
Not all of these bacteria do the same thing. Some are better at digesting some fibers than others. Some do generally good things for you, some do generally bad things for you (things that detract from your health).
The most direct way to change your intestinal bacteria (also called your 'gut flora,' which sounds better) is two steps: 1) flush out your own, basically taking a bunch of magnesium citrate and cleaning out your bowels, and 2) re-colonizing with a different set of species (either different species altogether, or just different ratios of the same strains of bacteria). Where would you get a replacement colony (see what I did there? colon? colony?) From the gut of a healthy person. The process is exactly as disgusting as you think.
Do we know for sure this will work?
What parts of this plan are supported by science? Actually, quite a bit, but not all of it.
We know (as in, have extremely solid scientific evidence) that gut bacteria can massively influence various things in rats. Scientists have done fecal transplants on obese rats and they got leaner, among many other similar experiments.
We know that the gut bacteria in healthy/lean/athletically advanced people are not the same as in sick/obese/athletically disadvantaged people.
We know that, for example, being insulin sensitive will make you a better martial artists or cyclist or whatever, even if only a little bit.
What do the naysayers say?
Why wouldn't this work? Naysayers argue that, while healthy/fit people have different gut flora than sick/unfit people, this might be an effect, not a cause. Maybe elite cyclists have different gut bacteria because of the lifestyle that made them elite, and the bacteria changes are just a side effect.
They may be right, but there are a lot of studies done on humans where various protocols are used to change gut flora that lead to changes in health markers. None of them have been done on cycling performance, but it seems very reasonable to think that some change in immune function or insulin sensitivity would be likely to improve performance, even if only a little bit.
Naysayers also argue that the helpfulness of a particular colony of bacteria (the strains and proportions of each strain) might be very specific to an individual - maybe the gut bacteria that make Dave a great cyclist wouldn't work for Dennis, because of some peculiarity of either Dave's or Dennis' physiology.
There are potential complications and downsides to this sort of treatment. By definition, fecal matter isn't sterile. Importing someone else's bacteria into your body might make you sick - especially if your immune system isn't up to snuff.
What should I do?
Let's be clear: nobody really knows just how much any particular person might gain, if anything, from changing their gut bacteria.
And that's a big part of the problem.
It's a good bet, in my opinion, that swapping out your gut flora for those of, for example, a high level athlete, would be good for you. People who tend towards obesity, poor immune function, bad insulin resistance, and compromised digestion don't usually end up at the top of the athletic pyramid. There's a really good chance that your average Olympic athlete has an above averagely good gut biome.
But that's a pretty shaky foundation to build on. If you're sickly, generally feel like crap, and are a well below average performer in many physical areas, and other avenues of traditional medical intervention haven't worked for you, this might be something to explore. You don't have as much to lose. But if you're generally doing okay, getting a fecal transplant from the UFC Featherweight Champion (Max Holloway, can I have some of your poop?) is probably not warranted. We just don't know if everyone benefits from the same bacteria, how long the effect would last (how long before my super Max Holloway colon returns to my current biome, given my lifestyle and eating habits?), or what negative effects there might be.
Having said that, it is very, very possible that in a few more years researchers will understand these variables a lot better. There might even be better ways to change your gut biome (better probiotics!)
You can do some things to change your gut flora right now that aren't nearly as radical as a fecal transplant. To be honest, any change in your diet is going to affect your gut flora - consuming different amounts or different types of fiber will feed the different strains better or worse, changing the composition of your gut biome. BUT nobody, as far as I can tell (and I've looked), fully understands which fibers feed which bacteria to get which specific desired (or undesired) result. Will eating raw potato starch result in a beneficial shift in your gut biome? Maybe. But if you look at the work of the people suggesting that, there are holes in their evidence. Like, there's a jump from "this fiber feeds gut bacteria!" to "bacteria are good for you!" without a lot of specifics about "this fiber feeds these bacteria more than these other ones, and having more of these and fewer of those will make you healthier."
Without knowing all the specifics, we can do a sort of "good enough for now" workaround: look at healthy populations, groups of very healthy people, and see if there are any commonalities in their diet, because there's a good chance that they're feeding their gut bacteria in a way that contributes to a positive gut biome. What do we see? Lots of vegetable intake, not a lot of processed foods. In other words, good amounts of fiber from a variety of natural plant sources (sorry, not orange metamucil).
Your gut bacteria are super important. Some strains are better for you than others, and in different amounts. It's very unclear exactly how to make sure you are supporting the good bacteria and interfering with the bad ones. BUT you're probably safe eating lots of fiber, from a variety of whole food sources, because there are huge populations of people who eat like that who seem to have, at the very least, not-bad gut biomes.
ALSO this looks a LOT like an area where, it's not that we have good reason to think that fecal transplants won't work, but we have strong reasons to think that they should, but probably not enough evidence to justify running out and pumping ourselves full of someone else's shit. So instead of filing this away as "probable hoax," file it away under "promising idea, wait for more work to be done."