That's something you really need to do your own research on, it's a big topic. Start by looking up 'complex carbohydrates' and consider that while they are made up of basic sugars, in nature the breakdown of those complex carbs would be done mostly in the gut rather than through refinement in a sugar plant. A pediatrician friend of mine doesn't even believe in consuming juice, because she considers the body is better able to regulate its sugar intake by processing the fruit and also using the non-nutritious bulk fiber of the fruit to regulate the amount consumed. This is her hunch rather than being proved through exhaustive research, but it seems like a fairly well-informed hunch.