Have green plant and protein powders been scientifically demonstrated to have substantial positive effects on health? what are the best ones?

Here's a better idea: If you were to believe 10% of the claim on the "supplement" sites, you'd be reading uncritically. I think every physician here will agree that health doesn't come out of a pill bottle. Eat wisely, avoid the greasy / sugary / salty stuff, and stay physically fit. You'll be around a better class of friends in any case. Cheers.

No, they haven't: Green plan & protein powders are popular based on the idea of having an easy alternative to eating veggies and fruits. For optimal health, the cdc recommends 2-4 cups of veggies & fruits per day. http://tinyurl.com/8v8yayq green powders are not really a substitute, though -- & none of the claims of need to "alkalize" your body because of eating an "acid" diet have been proven either. See comment.