This meta-analysis of 24 published studies on food colors, plus 10 more on dietary restriction, concluded that a restriction diet (e.g., the Feingold diet or an oligoantigenic diet) affects some children.
QUOTE: “Effects of food colors were notable but were susceptible to publication bias or were derived from small, nongeneralizable samples. Renewed investigation of diet and ADHD is warranted.”
NOTE: It is regrettable that most of the studies available to Nigg for analysis were the same old (OLD) studies; of the 24 studies included, 17 of them used 50 mg or less of food dyes. In fact, 3 of them used 15 mg or less of food dyes for their “challenge” materials. Of the remaining 7 studies, one (Rapp 1978) didn’t report how much was used, and one (David 1987) used a relatively high dosage but was challenging children whose parents had come to him for help because their response to the diet was unstable. This doesn’t leave a lot of useful studies for analysis.