V8 is acidic - any cooked tomatoes are acidic and will concequenty not make you feel very good :) Fresh, raw tomato juice from your juicer is great though, provided you don't eat any grains with it!
Tomatoes are a member of the nightshade family of plants.This family of plants is notorious for causing inflamation and pain.Tobbaco and pepper are also in this family.If you have issues with joint pain you might want to cut down or eliminate these foodstuffs that cause inflamation.
Hmm odd! If it's sleepiness with no pain, you may have some sort of allergy - tomato allergies aren't uncommon. Like trapper said, you may want to experiment with other members of the nightshade family and see if you have the same reaction.