Why does water make me urinate, but diet soda doesn't?

Factual Questions
1

Pretty simple question, but to flesh it out more:

I sometimes swing into a cycle of drinking vast quantities of diet soda. However much you are thinking, it is more than that…

But, for whatever reason, if I drink two liters of diet soda, it doesn’t seem to cause a need to urinate; which seems odd, as I was always told caffeine is a diuretic and probably should (and yes, I only drink caffeinated soda). But if I drink two liters of plain ol’ water, I will be struck with an urge to go shortly afterwards.

I wonder if the artificial sweeteners have some sort of anti-diuretic effect? Or if my body is just weird? So I thought I’d ask here!

2

I don’t know how large of an effect it has, but soda has sodium in it. Sodium can make you retain water. So, you probably are urinating out less.

3

Diet sodas tend to have more sodium than non-diet, but not a whole lot in the grand scheme of things. There has been some speculation that certain artificial sweeteners can cause water retention but apparently no large-scale human studies.

4

Likely confirmation bias

5

If you really want to test it, pee into a measuring container and check for 24h. You could go nuts and drink one thing first day and the other the next. My guess is you are peeing about the same volume, maybe more or less at a time. Average person pees seven times a day.

6

I drink caffeinated soda and water and not much else. I have noticed the opposite of the OP. I believe the soda gets me a feeling dehydrated at times and when I feel that I drink a lot of water, often a quart in a couple minutes. I won’t go for a while after that and shouldn’t have to because my kidneys are slowing down as my blood thins from the water.

Which reminds of when I first developed kidney problems and the doctor handed me a jug and told me to collect urine for 24 hours. I had jugs and bottles of urine everywhere until I figured out he only wanted mine.

7

How many jugs did the doctor give you? Good thing he wasn’t looking for fecal fat!

8

Only 7? I hate this croning phase.

9

I may have to do this. For science!

10

That’s what Howard Hughes said as well, initially.

11

But it isn’t about diet vs non-diet, it’s about diet soda vs water.

12

My uneducated hypothesis says that there is less to digest with water so it goes straight though you.

With the soda there’s more “processing” going on, thus it takes longer and less comes out. Or something science-y like that.

13

Is it possible that you tend to eat a lot of carbs with the diet soda and not with the water?

14

I was just adding to your point, since the OP specified diet which would amplify the effect a bit.