There's a great article in NYT today about this category. Mostly I think it's great because it talks about how the products really don't work. http://www.nytimes.com/2011/12/15/fashion/cosmetics-that-you-eat-or-drink.html?src=recg&pagewanted=all
"But do the products work? Many doctors say no (though others, like the dermatologists Dr. Fredric Brandt, Dr. Howard Murad and Dr. Nicholas Perricone, market supplements as part of their regimens). Good skin does not come from slickly marketed beauty drinks and foods, critics say, but from vegetables, whole foods and plain water."
Look, it's not horrible to drink or eat some of this stuff. If it tastes yummy then go for it. Everything in moderation (as Socrates and my dad always said/says). But plain ole water really is the best thing for your skin. Plus some supplementation, as directed by a dermatologist and/or esthetician, can be beneficial.