Parents have long observed that some kids go bonkers after eating foods with a lot of artificial ingredients or neon-bright colors. Medical researchers--not to mention the food industry--have been skeptical; there was no proof of this effect, at least nothing like a double-blind, controlled study.
As so often happens, however, the parents turned out to be a step ahead of the pros. A carefully designed study published in the British journal the Lancet shows that a variety of common food dyes and the preservative sodium benzoate--an ingredient in many soft drinks, fruit juices and salad dressings--do cause some kids to become measurably more hyperactive and distractible. The findings prompted Britain's Food Standards Agency to issue an immediate advisory to parents to limit their children's intake of additives if they notice an effect on behavior. In the U.S., there hasn't been a similar response, but doctors say it makes sense for parents to be on the alert.
The study, led by Jim Stevenson, a professor of psychology at England's University of Southampton, involved about 300 children in two age groups: 3-year-olds and 8- and 9-year-olds. Over three one-week periods, the children were randomly assigned to consume one of three fruit drinks daily: one contained the amount of dye and sodium benzoate typically found in a British child's diet, a second had a lower concentration of additives, and a third was additive-free. The children spent a week drinking each of the three mixtures, which looked and tasted alike. During each seven-day period, teachers, parents and graduate students (who did not know which drink the kids were getting) used standardized behavior-evaluation tools to size up such qualities as restlessness, lack of concentration, fidgeting and talking or interrupting too much.
Stevenson found that children in both age groups were significantly more hyperactive when drinking the beverage with higher levels of additives. Three-year-olds had a bigger response than the older kids did to the drink with the lower dose of additives, which had about the same amount of food coloring as in two 2-oz. (57 g) bags of candy. But even within each age group, some children responded strongly and others not at all. Stevenson's team is looking at how genetic differences may explain the range of sensitivity. One of his colleagues believes that the additives may trigger a release of histamines in sensitive kids. In general, the effects of the chemicals are not so great as to cause full-blown attention-deficit/hyperactivity disorder (ADHD). Still, the paper warns that "these adverse effects could affect the child's ability to benefit from the experience of school."
The Lancet paper may be the first to nail down a link between additives and hyperactivity, but as long ago as the 1970s, the idea was the basis for the restrictive Feingold diet, popularized as a treatment for ADHD. Some clinicians still routinely advise parents of kids with ADHD to steer their kids away from preservatives and food dyes. "It matters for some kids, so I tell parents to be their own scientist," says psychiatrist Edward Hallowell, author of several books on ADHD. While a similar link between hyperactivity and sugar remains unproven, Hallowell cautions parents to watch the sweets too. "I've seen too many kids who flip out after soda and birthday cake," he says. "I urge them to eat whole foods. They'll be healthier anyway."
The food industry has responded cautiously to the study, calling for further research. The food dyes used in the study "have gone through substantial safety evaluations by government bodies," notes Cathy Cook of the International Association of Color Manufacturers.
The Lancet study will probably encourage other researchers to conduct food-additive work of their own. People with disorders ranging from autism to atrial fibrillation (a heart condition) have claimed that preservatives worsen their symptoms. "My guess is that if we do similarly systematic work with other additives, we'd learn they, too, have implications for behavior," says Dr. James Perrin, a professor of pediatrics at Harvard. "Kids drink crazy things with colors that are almost flashing," he says. The study is one more reason to cheer the trend toward less processed, more natural fare.