We're finding out that fat [1] isn't actually bad for you, now salt, too. I wonder if we'll find out sugar is good for us, too, before long. [1] http://online.wsj.com/news/articles/SB1000142405270230367840...
And I believe they found that sugar does not cause hyperactivity, but somehow discovered that it helped either remember events better or learn new things.
Now looking back I think I had experienced that myself -- I remember my mom made some strawberry jam and I was eating it with a spoon for whatever reason, and it was while studying for a final oral exam in history (this is a different country, were we had to memorize and answer all 50 or so questions and then we'd be questioned on it orally by student). Anyway that one instance, out of many instances in years before before and after, I was remembering and at much higher rate. At least high enough to be noticeable to me.
Seeing the study years later kind of confirmed it.