Thanks to Bob Furguson for passing on this information from Dr. Frank Painter.
Today's (Sept. 7) New York Times discusses a new article just published in the English medical journal The Lancet. 
Their findings in this double-blinded and placebo-controlled trial confirm what Doris Rapp, MD  has been saying for years...that food colorings in children's food have a dramatic impact on behavior and attention span.
The study included (153) 3-year-olds and (144) 8/9-year-old children. They were given a drink containing food colorings and the preservative sodium benzoate. Virtually ALL the children from both groups experienced deteriorated attention spans, as reported by teachers and computerized attention testing. 
Here's a comment from an author: A mix of additives commonly found in children?s foods increases the mean level of hyperactivity, wrote the researchers, led by Jim Stevenson, a professor of psychology at the University of Southampton. ?The finding lends strong support for the case that food additives exacerbate hyperactive behaviors (inattention, impulsivity and overactivity) at least into middle childhood.?
The researchers also did a bit of hand-wringing about what impact this will have on the food industry and food spoilage. It makes me wonder if these folks live exclusively on packaged foods.
Another researcher asked: Even if it shows some increase in hyperactivity, is it clinically significant and does it impact the child's life? That makes me wonder if he has any small children.
He then asked: Is it powerful enough that you want to ostracize your kid? It is very socially impacting if children can't eat the things that their friends do. It's even more difficult, since many teachers provide food-colored candy treats as a way of managing class room behavior. Managing your child's diet may be challenging, but isn't that why God invented the parent?
I hope you will find this study of interest. It has already been added to the ADD/ADHD Page .
1] Some Food Additives Raise Hyperactivity, Study Finds
2] Doris Rapp, MD's website
3] Food Additives and Hyperactive Behavior in 3-year-old and 8/9-year-old Children in the Community: A Randomized, Double-blinded, Placebo-controlled Trial
4] The ADD/ADHD Page