Who has the healthier gastro intestinal tract - a vegan, vegetarian omnivore?

"all of the above": Healthy intestinal tract goes with healthy intestinal flora(microbes)-80%of the fecal mass.You can maintain that with fermented foods:yogurt, keffir, sauerkraut, pickles, .... Healthy flora helps the digestion and produces for us multiple vitamins from the b-s and k, that we absorb. We live in symbiosis with those bacteria helping each other. If you eat right - no gasses, regular bowel movement, ...

Balance: Higher animal protein intake associated with higher GI cancer growth rates, and probably incidence rates. The intestines &your mind need an adjustment period to move vegan. All the fiber of healthy plant foods may cause diarrhea a while. It may take time to find which foods your intestines tolerate well. There will be work involved in finding new recipes, but many good websites to help.