Grocery store shelves are full of foods in eye-catching colors. A bright blue sports drink or a rainbow cereal might look fun. But some scientists think that the synthetic dyes used to impart these colors could affect how some kids’ brains work. These chemicals might make it harder for them to focus or control their behavior.
In September 2024, California became the first state to ban some of these dyes from foods served by schools. Specifically, the new rules prohibit public schools from serving or selling foods containing six synthetic food dyes. The ban is set to begin in 2028.
Last October, protests broke out at the headquarters of WK Kellogg Co. Based in Battle Creek, Mich., the cereal maker has been criticized for breaking promises to remove synthetic food dyes in U.S. products.
The Food and Drug Administration, or FDA, oversees the safety of many U.S. food products. And it still approves the use of the same dyes that California will ban. According to FDA, there isn’t enough evidence to support a ban. Existing research doesn’t prove that synthetic dyes cause problems like hyperactivity, lack of focus or ADHD. (ADHD is short for attention deficit hyperactivity disorder.)
These different rules can be confusing.
Many sports and energy drinks contain synthetic dyes that will not be allowed in California public schools starting in 2028. SolStock/E+/Getty Images Plus
Because many foods contain synthetic food dyes, it’s hard for families to get clear advice on the risks of ingesting these dyes. It can also be tricky to find out which foods contain those dyes. Another complication: Experts think some children have stronger reactions to synthetic dyes than others.
Many experts believe California’s ban would protect the state’s public-school students. They’d like to see it inspire other states to pass similar laws. This could pressure food companies to change their recipes.
“I think it’s a great place to start, because school is an environment where kids need to be able to focus,” says Melanie Benesh. “They need to be able to feel like they are in control of their bodies.” Benesh works for a nonprofit organization, the Environmental Working Group. This Washington, D.C.-based group supported the California ban. Banning those dyes would create “a better learning environment for everyone,” she argues.
This debate over food dyes is far from over. So Science News Explores looked at how we got here and what the science says about the safety of these food colors.
What are synthetic food dyes and why are they in our food?
Synthetic dyes add color. Each dye has a unique chemical structure that absorbs specific frequencies of light. This allows our eyes to perceive a rainbow of colors in what would otherwise be bland-looking snacks. But these dyes don’t do much but add a splash of color. They don’t help preserve food. They have no nutritional value. Their only job is to make food look more tempting.
“A lot of these foods are candies, cereals — things that are marketed to kids,” Benesh notes. When manufacturers use a synthetic dye, it “makes their food more brightly colored, more attractive to kids. And I think it helps them sell their products.”
What products have synthetic dyes?
U.S. foods with synthetic dyes don’t need a warning label. Reading ingredient lists is often the only way to know if something contains one of these dyes. Usually they appear as a color name followed by a number (like “Yellow 5”). If you’re looking to avoid dyes, here are some common foods to watch out for:
Baked goods, such as cake mix, sugar cookies and gingerbread
Snack foods, such as Pop-Tarts, Cheetos and even some dried fruits
Candies, such as M&M’s, Skittles and Nerds
Cereals, such as Froot Loops, Trix and Lucky Charms
Beverages and specialty drinks, such as Electrolit, Pedialyte and Powerade
These synthetic dyes don’t show up only in foods. Some eyeshadows, hair products and medications contain one or more of the dyes soon to be banned in California.
When did scientists realize that synthetic dyes might be harmful?
Synthetic dyes have a long and troubled history. In the 1800s and early 1900s, companies colored food with poisonous substances. They made dyes that contained lead chromate, arsenic and coal tar. In 1950, dozens of children fell ill after eating Halloween candy. These treats had been tinted with a dangerous dye, Orange 1.
Many modern synthetic dyes were invented around the same time. Five of the six dyes in California’s ban were approved by FDA by 1931. Their potential to cause harm wasn’t widely discussed, however, until the mid-1970s.
That’s when the public first began to hear about a potential link between food dye and childhood hyperactivity, says Mari Golub. She studies how certain chemicals affect the way kids’ brains grow and develop. This toxicologist works at the University of California, Davis.
A flurry of research followed. Over the past 50 or so years, research on the effects of synthetic dyes has grown. Many scientists have reported a link between certain food dyes and behavioral changes in kids. These issues include mood swings, hyperactivity and an inability to focus.
Based on concerns about links to hyperactivity in kids, the FDA may consider banning a red food dye. Physician Kavita Patel describes how such concerns are evaluated.
So why did California ban six synthetic dyes?
An April 2021 report by the California Environmental Protection Agency (CalEPA) looked into potential risks from a whole range of synthetic dyes used in foods. These included Blue 1, Blue 2, Green 3, Red 40, Yellow 5 and Yellow 6 — the ones California is now going to ban in its public schools.
This report reviewed studies about how synthetic food dyes might be affecting children. They analyzed data from 25 clinical trials. These studies compared times when children ate foods colored by synthetic dyes to times when they ate foods without dyes. In many of the trials, parents and teachers were asked to note any hyperactivity issues as they arose.
The report turned up 16 studies showing a credible link between dye consumption and adverse behavior in a child.
School meals contain many foods, such as Jell-O, baked goods and other snacks, that get their colors from synthetic food dyes. Beginning in 2028, such dyes won’t be allowed in California public schools.Yellow Dog Productions/The Image Bank/Getty
But finding a link is not the same as proving it was the cause of that change. Scientists needed more information.
That’s where animal studies come in.
In animals, the link between synthetic food dyes and behavior is much clearer. Researchers have given synthetic dyes to rats, mice and rabbits. Afterward, the animals became hyperactive or showed signs of memory loss.
Animal studies can be important tools for comparison. Still, they do have their limits. For instance, scientists can measure precisely how much food dye they give to rats in the lab. It’s hard to tally how much dye a child has eaten in sprinkles, chips and cookies.
But animal studies have shown that dyes do affect the brains of exposed animals. They also help scientists determine which dyes and doses start to create negative effects, says physician Mark Miller. He studies how the environment affects children’s health. Miller works at California’s Office of Environmental Health Hazard Assessment in Oakland. He was part of the team that wrote CalEPA’s 2021 report.
Why was California’s decision controversial?
Not everyone supports California’s ban.
“Consistency in food regulations across states and federal agencies is critical for ensuring public confidence,” says chemist Sean Taylor. He works in Washington, D.C., for the International Association of Color Manufacturers. Taylor notes that FDA reviewed scientific studies, too. A 2016 report by FDA scientists found no clear proof that synthetic dyes directly cause unwanted behaviors in children.
Technically, FDA and CalEPA’s report don’t contradict each other. FDA found no proof that the dyes cause a problem. California’s researchers saw a link between dyes and behavior. But they can’t completely prove the dyes were responsible — and not some other possible causes.
It’s hard to prove any danger due to food dyes. One reason: There aren’t many studies that have looked into this. To identify a clear cause, scientists would need to compare two groups of children. One group would not have consumed any food dyes. The other would eat foods with specific doses of synthetic dyes.
This would be very hard to do. And to date, no one has done such a comparison.
Scientists lack “gold-standard causal data,” admits Amy Gilson in Sacramento. She, too, works for CalEPA in its Office of Environmental Health Hazard Assessment. In fact, she notes, it’s unlikely that such a clear, black-and-white comparison will ever be published.
But, Gilson adds, scientists don’t need perfect proof to recognize good evidence. “There’s good science that points us to needing to take some action.”
