Kraft Macaroni & Cheese—that favorite food of kids, packaged in the nostalgic blue box—will soon be free of yellow dye. Kraft announced Monday that it will remove artificial food coloring, notably Yellow No. 5 and Yellow No. 6 dyes, from its iconic product by January 2016. Instead, the pasta will maintain its bright yellow color by using natural ingredients: paprika, turmeric and annatto (the latter of which is derived from achiote tree seeds).



The company said it decided to pull the dyes in response to growing consumer pressure for more natural foods. But claims that the dyes may be linked to attention-deficit hyperactivity disorder (ADHD) in children have also risen recently, as they did years ago, putting food dyes under sharp focus once again. On its Web site Kraft says synthetic colors are not harmful, and that their motivation to remove them is because consumers want more foods with no artificial colors.



The U.S. Food and Drug Administration maintains artificial food dyes are safe but some research studies have found the dyes can contribute to hyperactive behavior in children. Food dyes have been controversial since pediatrician Benjamin Feingold published findings in the 1970s that suggested a link between artificial colors and hyperactive behavior, but scientists, consumers and the government have not yet reached a consensus on the extent of this risk or the correct path to address it.



After a 2007 study in the U.K. showed that artificial colors and/or the common preservative sodium benzoate increased hyperactivity in children, the European Union started requiring food labels indicating that a product contains any one of six dyes that had been investigated. The label states the product "may have an adverse effect on activity and attention in children." The FDA convened a Food Advisory Committee meeting in 2011 to review the existing research, and concluded that there was not sufficient evidence proving that foods with artificial colors caused hyperactivity in the general population. The FDA also decided that further research was needed, and that a label disclosing a possible link between dyes and hyperactivity was unnecessary.



But Joel Nigg, professor of psychiatry, pediatrics and behavioral neuroscience at Oregon Health & Science University, says the studies support the link between dyes and hyperactivity. "The literature here is so sparse that on the one hand you can sympathize with those who want to take a wait-and-see attitude. But on the other hand, when we do look at the literature we have, it's surprising that we do see effects that seem to be real," he says. "Do you want to take a chance that these initial studies are wrong and put kids at risk or do you want to take a chance that they're right? We have to work on the data we have."



A 2012 meta-analysis of studies co-authored by Nigg concluded that color additives have an effect on hyperactive behavior in children, with a small subset showing more extreme behavior than others. He also concluded that further research was needed because so many of the studies looked at only small numbers of people or could not draw conclusions about the general population. Studies have also shown removing foods containing artificial dyes via restriction diets can successfully decrease hyperactivity but Nigg says this is likely because removing processed foods in general is healthier and results in better behavioral outcomes for children with ADHD.



Companies typically add artificial colors to make their products look more appetizing. The chemicals Yellow Nos. 5 and 6 have been in use since the early 1900s, and the FDA approved them for use in 1969 and 1986, respectively. They are two of the nine certified colors that food manufacturers must list on ingredient labels. According to the FDA, Yellow No. 5 can cause an allergic reaction for one out of every 10,000 people. The amount of dye the FDA has deemed acceptable for daily intake, or ADI, is five milligrams per kilogram of body weight per day (mg/kg bw/day) for Yellow No. 5 and 3.75 mg/kg bw/day for Yellow No. 6. An April 2015 study looked at how much dye was in recommended servings of processed foods; it found Kraft Macaroni & Cheese contained 17.6 milligrams of Yellow Nos. 5 or 6 per one-cup serving. Because the chemicals are so similar in color, and thus difficult to tell apart in measurements, the researchers chose the dye that allowed the highest concentration. For a child weighing 30 kilograms (about 65 pounds), this translates to 0.59 mg/kg bw per serving.



Bernard Weiss, professor emeritus of the Department of Environmental Medicine at the University of Rochester Medical Center who has researched this issue for decades, says he is frustrated that the FDA has not acted on the research showing the connection between artificial dyes and hyperactivity. "All the evidence we have has showed that it has some capacity to harm," he says. "In Europe that's enough to get it banned because a manufacturer has to show lack of toxic effects. In this country it's up to the government to find out whether or not there are harmful effects." Weiss supports banning artificial colors until companies have evidence that they cause no harm. Like most other scientists in this field, he thinks more research, particularly investigating dyes' effects on the developing brain, is imperative.



Nigg says the FDA should require manufacturers to include a label saying artificial colors could affect hyperactivity in some children, like the E.U. does. "I think the most important thing we've seen in our research is that there's a subgroup of kids that seems to respond much more to these types of things, and that group is what I worry about.” The only way to protect that subgroup, he says, “is to protect everybody. We don't have to alarm the public to inform the public."