Snitzer1, I hope you've seen other threads with this same subject discussed. There is also an Entyvio Support group listed on the front page where its been discussed too.
I'm about to switch from Humira to Entyvio so I'm interested in your post and others about it.
Following my Entyvio infusions, I have had severe fatigue, having to go #2 up to sixteen times a day, body temp fluctuations, cramps in the lower abdomen (just above the bladder area going across the waist which required Tylenol now and then) and despite the BS my GI doctor has given me, I KNOW that my vision was better before I began the Entyvio and several other people have stated similar problems.
If your GI doctor(s) refuse to acknowledge that diet plays a part in IBS and IBD, then find a new one. I sure as hell am going to.
I am not trying to dissuade you from getting your Entyvio therapy, but to consider that this has the potential to give people PML which can demylelinate the neurons in your brain: At first, Entyvio did not list this as a possible side-effect but I recently saw a commercial for it and it listed PML as a rare but possible side-effect.
By sheer luck, when I was on Remicade (over three-years ago), it began to help me within two weeks, but I was dumb enough to stop it because I thought that my vegan (FORMER) diet had "healed me" and I can not go back on the Remicade because I have supposedly built up antibodies to it.