I have the same questions Tyler as I've been juicing for several years now. I wonder if the sugars in juicing stress the pancreas. I keep juicing though.
One of the "superfood" recipes in the NT cookbook is for carrot juice with cream added to convert the betacarotene to Vitamin A, so they can't be that against juicing.
I've made the beet kvass and I like it but I add beet juice to my juices so maybe I'm used to the taste. I've started grinding a TBSPN of flax seeds and soaking them in 4oz beet kvass every morning then drinking it.