If I remember my highschool biology correctly (which I probably don't, so take this with all the grains of salt), natural sources like berries, fruits, etc... create natural glucose which is what every living organism (including us...use for energy). Meaning when we eat berries and fruit, that natural glucose doesn't need to be converted or processed in order for our body to make use of it. That also gives it a more stable effect in our system.
Refined sugars, on the other hand, need to be processed into glucose before it can bind to (oxygen? I think?) and pass into our bloodstream. That process leaves a lot of junk leftover which can have detrimental effects.
Again...I'm trying to remember a 35 year old highschool biology course, so correct me if I'm wrong.