Soy would cause me more gas than would milk....
Try not to use the term no-no regarding foods in regards to UC. Some bother people, some exacerbate discomfort, some don't cause any noticable symptoms at all. Food doesn't cause flares.
What symptoms are you having that is encouraging you to switch?
Most of us can be lactose intolerant....and when flaring, can cause more discomfort. Some will get gas regardless, and sometimes find that Lactaid milk or Lactaid pills helps lessen the symptoms.
Some female UCers have estrogen sensitive flares...soy is naturally high in estrogen, so...for some it might not be the best choice. Not to say that would be a bad choice for you....definitely try it, and if you have discomfort, then it's not a best choice.
Another option is Rice Dream....very refreshing!
Sometimes moderation is the key...finding the amount can be a pain, however.
If I haven't already....welcome to the forum.
What meds are you on?
*Heather*Status: mini flare Dec 28... tapered to every 4th night
~diagnosed January 1989 UC (proctosigmoiditis)
~5ASA: Asacol (6 daily) + Salofalk enemas (increase for flares tapered to maintenance)
~Bentylol (dicyclomine) 20mg as needed
~Probiotic 3(Natural Factors Protec) bedtime + 1 (Primadophilus Reuteri) occasionally
~multi-digestive enzymes as needed ....zymactive 3 - 5x daily
~Ranitidine,Pariet (reflux) Effexor XR 75mg; Pulmicort/Airomir (asthma)
~URSO for PSC (or PBC) 500mg X 2 daily (LFTs back to NORMAL!!)
My doc's logic.. "TREAT (FROM)BOTH ENDS" worth it !!!