The cocktail of artificial extras in drinks, sweets and processed foods can also make them more impulsive and inattentive, said researchers.

The Food Standards Agency immediately warned parents of hyperactive children to cut the additives from their diet.

Dr. Andrew Wadge, FSA chief scientist, said, "We have revised our advice.

"If a child shows signs of hyperactivity or attention deficit hyperactivity disorder, eliminating the colors used in the study from their diet might have some beneficial effects."

Scientists at Southampton University found certain artificial colors and sodium bezoate preservative had harmful effects on behavior.

They were sunset yellow (E110), tartrazine (E102), carmoisine (E122), ponceau 4R (E124), quinoline yellow (E104), allura red (E129) and sodium benzoate (E211). The results are published in the Lancet medical journal. Report author Professor Jim Stevenson said taking them out of food would not end hyperactive disorders "but they are something a child can avoid."

Richard Watts, of the Children's Food Campaign, said, "The junk food diet turns out to be bad for children's mental health as well as their physical health."

Marks & Spencer is removing all artificial colors and flavors from 99% of products.

Asda is doing the same with 9,000 "own label" items. Sainsbury's, Tesco and Co-op also plan to act.

The Food and Drinks Federation said, "The industry continues to reduce the use of additives and many products contain no artificial colors."

The British Soft Drinks Association said, "The industry will study the findings."

From the September 10, 2007, Prepared Foods e-Flash