n = 1 but I clearly feel the effect when I start drinking aspartam drinks a few times a week. So much so that I just stopped drinking them.

I didn't use to. But I stopped rafined sugar for a year and compensated with coca zero. After that, guts never been quite the same and it took some copious amount of probiotics with regular doctor checks to feel better.

Even then, it's still no back up to baseline, and now drinking aspartam more than once is upsetting.

People say this about MSG too, but when you blind-test them the effect vanishes, which is unsurprising because the constituents in MSG are, like aspartame, widely prevalent in traditional foodstuffs.