I have seen that idea popularized here on HN for sure - it seems almost every physical or mental health and diet related post gets a comment about "the gut microbiome" which either mentions or is replied to by a comment that claims diet soda "destroys" it. The frequency with which this is mentioned is definitely pretty high, but I've not come across any links to studies or further reading on the idea.
EDIT:
Here is what I believe to be a source of many such claims, a 2014 study suggesting that artificial sweeteners can alter gut flora in mice to lead them to being glucose intolerant: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4615743/
I'd be interested if there's anything more recent or conclusive about this - plenty of sensationalistic articles seem to be out there either extrapolating from or challenging this study, but I'm not able to deduce anything further.
My low-information read of the current state of knowledge is: we've established at very high confidence that the gut microbiome really is very important.
And that's it; we don't know anything more detailed than that.
There's also a probiotic called visbiome (formerly* known as vsl #3, which is the name the research literature uses) that has shown a lot of effectiveness for IBS and similar issues. I don't feel like digging up the studies for that unfortunately but there's quite a bit of evidence.
* vsl #3 is still marketed but is supposedly a different manufacturing process now. thus visbiome is now the "real" one
But intuitively eating unprocessed foods that are not made with artificial or chemical anything (including artificial sweeteners) is probably a good start.
Fasting is probably another good way to reset your gut.
I don't think "resetting your gut" is a good way to think about it. Taking oral antibiotics will "reset your gut", in the sense of killing most of the existing biome and leaving space for new flora to grow into, but that can lead to problems as the biome that develops from a clean field isn't the same as the standard biome. To the best of my knowledge, you normally inherit your gut flora from your mother during birth and nursing, and then your gut hopefully stays stable over time. "Resetting" is more likely to give you a worse biome than a better one.
Is it because diet soda doesn't provide nutrition to gut bacteria, but still takes up the space actual nutrition could have been in, and thus the gut bacteria don't get access to as much nutrition?
Edit: poor wording above. I meant to ask whether the artificial sweeteners could take the place of nutrition for the gut bacteria but not actually provide enough nutrition.
Ah, I should've written a more generic "takes the place of" instead of space. I meant to ask something along the lines of whether the artificial sweeteners of diet sugar might be confused for nutrition by the gut bacteria. Basically, I was picturing a situation where the gut bacteria might try to "eat" the artificial sweeteners, but then don't end up getting enough energy from it and can't do the things they need to do.
Good point. I worded it very poorly and your answer would definitely fit. I meant to ask whether the artificial sweeteners in diet soda were taking the place of nutrition for the gut bacteria, but don't end up giving the bacteria enough energy/resources to live on.
Kimchi - full of pro-biotics and good for your gut, apparently - is what makes my farts smell worst of all. Worst incident was a freshly-home-made batch, played bass in a show the after eating it at dinnertime and the smell actually made the drummer vomit :(
EDIT: Here is what I believe to be a source of many such claims, a 2014 study suggesting that artificial sweeteners can alter gut flora in mice to lead them to being glucose intolerant: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4615743/
I'd be interested if there's anything more recent or conclusive about this - plenty of sensationalistic articles seem to be out there either extrapolating from or challenging this study, but I'm not able to deduce anything further.