I agree that centrifugical juicers destory enzymes and do not extract nutrients very well. They mostly just extract Sugar and water.
To optimize the effect of juicing it is best to use an auger type of juicer to mash the the vegetable matter and then use a press to juice the pulp. You get substantially more nutrients that way. I suggest anyone who does juice, to use lots of greens in their juice. The key is minerals vs sugar.
Also green smoothies are excellent but people who have poor digestion and need the benefits of fast nutrition due to illness, to use the juicing outlined in Gerson therapy.