Have you assessed the nutritional content in the final juice? Carrots and celery are known to be harmful in excess (as most things are).
90 days is a very long time, please talk to a doctor or nutritionist before attempting anything like this.
You may also look into the fact you’re eating a zero-fiber diet. I’ve read something about that actually helping with IBS symptoms, it could explain any improvement you see vs the content of the diet which honestly doesn’t sound great.
It's not just "tons", it's exclusively vegetables which is probably fine as long as you make sure your diet is balanced.
However only drinking "juices" certainly for 3 months seems a bit wacky (of course it still depends on the specific fruits/vegetables). Chances are you'll consume significantly more sugar and significantly less protein and fat (of course fiber deosen't seem to matter..) compared to actually eating those vegetables/fruits directly. Which seems like a horrible idea..
No worries. “Eating” is not even the right word since you’re removing all solids. Without seeing any evidence or scientific argument, yes, drinking juice of the same four vegetables for a full three months sounds very problematic on multiple fronts… this is very different from “eating a lot of vegetables”.
I'm not forcing anyone to do it. I've done it, and had great results. I've had a few friends and family do it, and all have been impressed.
People think nothing of going on vacation and eating poorly and drinking for 7+ days straight.
But tell people you should try atleast 7 days of vegetable juice only and they start looking at your sideways. Say 30+ days and they'll warn you it's dangerous. Say 90 and they'll think you're going to die.
I promise you more people are dying from pizza and beer than vegetable juice for 90 days.
