I need more greens/vegetables.....

I don't mind the taste of fresh squeezed veggie juice, and rather prefer it's convenience around lunch time. So I've been getting a 12 oz. "Green Goddess" - kale, spinach, cucumber, celery, and I'm not sure what else.....

2 questions:

What's the approximate caloric content of one of these bad boys (I want to make sure I'm not overdoing it)?

Does the spinach juice add any significant protein?

I tried asking these questions to one of the staff members at the Natural Food store but I was met with kind of a blank stare. I guess it was a blasphemous question - somehow doubting the magical powers of this elixir.....

Thanks!!