Although the body of evidence may not be large, a few well-designed studies have swayed entire governments, and even the American Academy of Pediatrics (AAP), to reconsider the health effects of artificial food colors.

In 2004, David Schab published a groundbreaking meta-analysis looking at three decades worth of research on food dyes and hyperactivity in children.

At first, skepticism fueled his interest. “There were a lot of really poorly conducted studies out there that concluded with unconvincing and over-reaching claims,” recalls Schab, PhD, an assistant clinical professor of psychiatry at Columbia University. But once he weeded out the bad studies, “Artificial food colorings appeared, in the highest quality of studies, to promote behavioral disturbances in hyperactive children,” Schab says.

According to the researcher, the mechanism by which synthetic dyes impact behavior remains unclear, but they likely interfere with transmission of the neurotransmitter dopamine, which plays a critical role in attention.

Another lingering question: Do they impact only a certain subset of children, already prone to hyperactivity, or are all kids at risk?

Schab believes that question was answered by researchers at the University of Southhampton in the United Kingdom. They administered either an artificially colored drink or a dye-free alternative to 153 3-year-olds and 144 8-year-olds after they had stripped dyes from their diet for six weeks. Assessments from parents and teachers showed “significantly higher hyperactivity scores” in kids within hours after consuming the colored drinks.

In a 2007 study published in the Lancet, the University of Southhampton researchers concluded that “the adverse effects are not just seen in children with extreme hyperactivity but can also be seen in the general population.”

The study was not without flaws. For example, it used six colors and a preservative called sodium benzoate—making it impossible to isolate which compound was to blame.

Nonetheless, the American Academy of Pediatrics released a statement soon after suggesting that “a trial of a preservative-free, food coloring-free diet is a reasonable intervention,” for kids with hyperactivity problems. An accompanying AAP editorial added: “We skeptics might have been wrong.”

Government action: U.S. vs. U.K.

In the U.K., the European Parliament asked food manufacturers to voluntarily remove synthetic dyes from food by Dec. 31, 2009. In what many see as a de-facto ban, it now requires foods containing them to sport a damning label: “May have an adverse effect on activity and attention in children.”

Australia and Canada are now considering similar moves and at least one U.S. state, Maryland, has proposed a ban on food dyes in school lunches.

Meanwhile, parents in the United States are feeling snubbed. “There are people out there who will never even suspect this—who will never know what’s wrong with their children,” says Shutters, who was the first to sign up for the FDA hearing. “Our government needs to protect our kids too.”

And it’s not just the governments that are behaving differently on the issue of dyes. Responding to consumer pressure and the U.K.’s labeling laws, numerous multi-conglomerate food companies, including Mars Inc. and Kraft Foods Inc., have removed artificial colors from their products sold in Britain—while still selling those same synthetically colored products in America.