“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.”

Still, Dr. Spencer called the advice of the British food agency “sensible,” noting that some children may be “supersensitive to additives” just as some people are more sensitive to caffeine.

The Lancet study focused on a variety of food colorings and on sodium benzoate, a common preservative. The researchers note that removing this preservative from food could cause problems in itself by increasing spoilage. In the six-week trial, researchers gave a randomly selected group of several hundred 3-year-olds and of 8- and 9-year-olds drinks with additives — colors and sodium benzoate — that mimicked the mix in children’s drinks that are commercially available. The dose of additives consumed was equivalent to that in one or two servings of candy a day, the researchers said. Their diet was otherwise controlled to avoid other sources of the additives.

A control group was given an additive-free placebo drink that looked and tasted the same.

All of the children were evaluated for inattention and hyperactivity by parents, teachers (for school-age children) and through a computer test. Neither the researchers nor the subject knew which drink any of the children had consumed.

The researchers discovered that children in both age groups were significantly more hyperactive and that they had shorter attention spans if they had consumed the drink containing the additives. The study did not try to link specific consumption with specific behaviors. The study’s authors noted that other research suggested that the hyperactivity could increase in as little as an hour after artificial additives were consumed.

The Lancet study could not determine which of the additives caused the poor performances because all the children received a mix. “This was a very complicated study, and it will take an even more complicated study to figure out which components caused the effect,” Professor Stevenson said.