Hi Maximus,
This is one of the healthiest actions you can take. Kale is the best by far and the amount of nutrition you get in the form of Vitamin A, C, lutein, xanthein (don't know if that is right)chloraphyl, etc. is incredible. Turnip greens and collards are huge, too, but kale leaves them in the dust. Half a cup of juice, once or twice is a day is all you need and you can stir fry the pulp with olive oil and what ever spices you want for the fiber.
Enjoy, yb.