Este artículo estará disponible en español en El Tiempo Latino.
In recent weeks, Health and Human Services Secretary Robert F. Kennedy Jr. has said that “very, very strong studies” link food dyes to cancer and ADHD. Experts are concerned about the impacts of unhealthy diets and obesity in the U.S., but some say Kennedy overstates the role of food dyes in chronic disease.
The dyes haven’t been shown to cause cancer in humans. Studies show a possible link to symptoms of attention-deficit/hyperactivity disorder in children.
Recently, Kennedy has taken his “Make America Healthy Again” campaign on the road, appearing in some states that have passed legislation to limit food dyes and other additives. So far, governors in California, Arizona, Utah, Virginia and West Virginia have signed laws disallowing certain food dyes from school meals, some beginning as soon as later this year, and West Virginia also enacted a law that will ban seven synthetic food dyes outright from sale in the state beginning in 2028. Lawmakers in two dozen additional states have introduced or passed bills that would restrict synthetic food dyes, which are present in a variety of foods, from soft drinks to cereal.
“So the loneliness, the dispossession, the crisis that we have in mental health, in suicide, in ADD, ADHD, all of these are linked — and particularly to the dyes,” Kennedy said in a March 28 speech in West Virginia, given alongside Gov. Patrick Morrisey. “It’s very clear the dyes that Gov. Morrisey is banning, all of them are linked in very, very strong studies to ADHD and to cancers. So we’re seeing an explosion in cancers in this country.”
Kennedy also spoke about food dyes in an April 8 interview on CBS News, following a stop in Arizona to celebrate legislation to ban food dyes and other additives in school lunches, as well as a law aiming to ban use of Supplemental Nutrition Assistance Program funds to purchase sodas. “The food dyes are kind of the most egregious,” Kennedy told CBS. “They don’t use them in any other country. They’re clearly associated with a variety — a grim inventory — of diseases, including cancers and behavioral disease and neurological disease like ADHD, and it’s very, very well-documented.”
We reached out to HHS to ask about the research Kennedy was referring to, but we did not receive a reply.
The evidence linking food dyes and cancer comes from studies in animals and cells. There isn’t evidence food dyes are driving an increase in cancer in humans, Susan Mayne, who served as director of the Center for Food Safety and Applied Nutrition at the U.S. Food and Drug Administration between 2015 and 2023, told us.
“We are seeing rising rates of the obesity-related cancers, and especially in young people, and that is concerning,” she said. “But focusing in on risk factors where there’s really no significant scientific evidence indicating that they are causing these cancers while omitting ones we know are is really undermining public health.” Mayne spent much of her career studying nutrition, epidemiology and cancer at Yale School of Public Health, where she is now an adjunct professor.
Some research suggests that food dyes lead to neurobehavioral changes in some children. But the literature is mixed and opinions vary on the strength of the evidence.
“The totality of scientific evidence indicates that most children have no adverse effects when consuming foods containing color additives, but some evidence suggests that certain children may be sensitive to them,” the FDA says on its website in the answer to a question about food dyes and child behavior.
Kennedy is also incorrect in categorically stating that food dyes aren’t used in any other country. Regulations on food dyes vary around the world, and companies have reformulated some foods to eliminate synthetic dyes for certain markets. The European Union, for example, requires that foods containing certain food colors have warning labels stating that they “may have an adverse effect on activity and attention in children.” However, synthetic food dyes are allowed outside the U.S.
Some researchers and advocacy groups have said the bar for evidence on food dyes’ harms should be low, based on their lack of benefits for consumers.
“These are entirely unnecessary when we are talking about nutrition and food safety,” Thomas Galligan, principal scientist for food additives and supplements at the nonprofit Center for Science in the Public Interest, told us, differentiating them from additives with some use, such as preservatives that keep food from going bad. “They are strictly a money-making tool for food companies, and so our tolerance for the risk, so to speak, is extremely low in the case of food dyes.” CSPI has advocated a ban on synthetic food dyes.
The organization also has advocated the tightening of the GRAS, or generally recognized as safe, pathway — a way for food companies to add new ingredients to their foods without undergoing FDA review. Kennedy has told the FDA to explore revising the GRAS pathway.
“Colorants are unnecessary … so they should be out totally,” Dr. John O. Warner, a pediatrician and professor emeritus at Imperial College London who has studied the effects of synthetic food dyes and other additives on children’s behavior, told us. He said a switch to natural colors would be positive but that it is necessary to shift people’s diets overall to more natural foods and less ultraprocessed foods. “It’s not only the additives which are being shown to have the potential for adverse effects” in ultraprocessed foods, he said. “It’s the original food and the way it’s processed that could also be having an adverse effect.”
“I am all for getting rid of artificial colors and closing the GRAS loophole but neither of those is a major cause of obesity and its health consequences,” Marion Nestle, a professor emerita of nutrition, food studies and public health at New York University, wrote on April 2 on her blog, Food Politics.
Other researchers have expressed concern that an overly narrow focus on food dyes or other specific additives — combined with cuts to the federal workforce and programs, and the weakening of environmental regulations — will not meaningfully transform Americans’ health.
“We’re hearing all this rhetoric from RFK Jr. about how he wants to fix the food system, but then he’s making massive cuts within HHS and FDA that will directly impede his ability to fix the food system,” Galligan said.
Food Dyes Not Established to Cause Human Cancers
Kennedy’s comments give the incorrect impression that FDA-approved synthetic food dyes are a well-established cause of cancer.
“The only food additives for which evidence has shown a link with cancer are nitrites and nitrates, which are used as preservatives in processed meat,” the American Institute for Cancer Research states on its website. “Eating processed meat is strongly associated with an increased risk of colorectal cancer. There is currently no other strong evidence linking food additives to an increased cancer risk.”
“I think the evidence that the approved food colorings cause cancer is very slim,” Dr. Ronald Kleinman, a pediatrician who studies nutrition at MassGeneral Hospital for Children, told us.
Two studies whose results were published in 1987 indicated that Red 3 caused cancer in male laboratory rats. Based on this research and following a 2022 petition from consumer advocacy groups, the FDA on Jan. 15 announced a ban of Red 3 in food and drugs, which will take effect in 2027 for food and 2028 for drugs. But the agency said that it was banning the dye due to a requirement under law to ban any food additive that has been shown to cause cancer in animals — and not due to concern that the dye caused cancer in people.
The dye caused cancer “due to a rat specific hormonal mechanism” that does not apply in humans, according to the agency, and people are not usually exposed to the levels of dye shown to cause cancer in male rats. Claims that the dye’s presence in food or drugs “puts people at risk are not supported by the available scientific information,” the FDA website says.
“I think there’s a good process in place to review whether the … dyes cause cancer,” Kleinman said. “For all of those that have been approved, we can be pretty certain at this point that there is no evidence that they cause cancer and move on.”
The overall data also do not support Kennedy’s statement that there has been an “explosion” in cancers. Cancer mortality has been declining in the U.S. since the 1990s, in both men and women. Incidence also has declined in men since its peak in the 1990s, although it has risen gradually in women over this period. (A major factor driving a cancer spike in the 1990s in men was the rise of PSA testing, which can identify slow-growing prostate cancers that would have never gone on to cause harm.)
The mortality rates “went up very high some decades ago, and that was because of the huge impact of smoking on lung cancer in both men and women, and that dominated the entire mortality data because lung cancer was so common and so lethal,” Mayne explained. “And then with public health interventions to reduce smoking, we saw a decrease in cancer mortality. First it started in men, followed behind that in women.” The decline in cancer deaths has also been driven by improvements in cancer screening and treatment, according to the American Cancer Society.
Cancers have varied risk factors, Mayne said, and some cancers — such as adenocarcinoma of the esophagus and uterine cancer — have risen in recent decades. There is also a pattern of increased cancer risk emerging in younger generations, due to a rise in obesity and other known and unknown factors, according to the ACS.
“The wonderful public health gains we made with tobacco control have been eroded by the growing prevalence of obesity in this country,” Mayne said.
What people eat and drink also can increase the risk for specific cancers independent of obesity. For instance, research “very consistently” shows that diets low in fiber-containing foods, such as fruits, vegetables and whole grains, are associated with a higher risk of colon cancer, Mayne said. Consuming more meat — and particularly processed meat — is associated with an increased risk of colorectal cancer, she said. And drinking more alcohol is associated with increased risk of a variety of cancers.
To reduce risk of cancer overall, Mayne emphasized the importance of avoiding excess alcohol, avoiding tobacco, vaccinating against human papillomavirus for younger people, maintaining a healthy body weight and eating a high-quality diet.
Other researchers acknowledged the research on food dyes and cancer in humans is limited but expressed concern about possible risks.
Galligan of CSPI agreed that “we don’t have direct evidence Red 3 causes cancer in humans,” but he said that studies to investigate this in humans would be “hard to conduct” and argued that the available evidence supported banning the dye. His organization was among those that petitioned to ban Red 3 based on the rat data.
Lorne Hofseth, director of the Center for Colon Cancer Research at the University of South Carolina, expressed concern that approved dyes could cause inflammation and DNA damage, which are mechanisms for increasing the risk of cancer. The dyes “tickle the players involved in carcinogenesis,” he told us.
A Possible Link Between Food Dyes and ADHD Symptoms
Joel Nigg, a clinical psychologist at Oregon Health & Science University, told us in an email that ADHD has many causes working in concert. Perhaps the largest single contributing factor is genetics, he said, but there are also multiple environmental factors that either protect against or help cause ADHD, “especially early in development.”
Some studies have found a connection between consuming synthetic food dyes and ADHD symptoms, which include inattention, impulsivity and hyperactivity.
“Thus, it is fair to say that food dyes are associated with ADHD and do make a modest contribution to it, but are not the major cause,” Nigg said.
These include challenge studies, in which children avoided food dyes and sometimes other additives for a period and then were randomly assigned at certain intervals to consume drinks or foods containing either these additives or a placebo.
Researchers at the University of Southampton in the U.K. in the early 2000s, for example, had around 1,800 3-year-old children from the general population stop consuming synthetic food colorings and a type of preservative for a week, before randomly assigning them to consume drinks either containing the substances or not. The children’s parents reported an increase in hyperactivity with both the placebo drinks and the additive-containing drinks, but the increase in hyperactivity was greater with the drinks containing the additives. Clinicians unrelated to the children did not detect a difference in behavior in children who did versus did not receive the additives.
Subsequently, the researchers did a similar study in around 300 additional 3-year-olds and 8- and 9-year-olds, using two mixtures of food dyes and additives. This study relied on parent and teacher reports, as well as results of a computerized test for the older children. One mix had a small but statistically significant influence on behavioral changes in both age groups. A different mix showed an influence in the older children, but not the younger ones.
Other studies, however, have not identified any effect of food dyes on behavior. Overall, the literature is mixed, with studies arriving at varying conclusions, perhaps because of differences in methodology, the populations studied and the additives included.
Some review studies have nevertheless found the link between food dyes and behavioral changes to be convincing.
“Overall, our review of human studies suggests that synthetic food dyes are associated with adverse neurobehavioral effects, such as inattentiveness, hyperactivity and restlessness in sensitive children,” a 2021 report from California’s Office of Environmental Health Hazard Assessment concluded.
Nigg in 2012 co-authored a meta-analysis that found that an “estimated 8% of children with ADHD may have symptoms related to synthetic food colors.” He told us he believed that eliminating synthetic food dyes in the U.S. “would have a small effect on reducing symptoms of inattention and cases of ADHD.”
However, Nigg said that to “really reduce environmental contributors to ADHD, it would be important to also address other equally if not more important factors.” These include reducing exposure to lead in the environment, certain types of air pollution, other chemicals, and possibly pesticides and herbicides.
And he emphasized the importance of preventing exposures in the womb, adding that low birthweight “is a major contributor to ADHD.”
“Overall, dietary factors are relevant, but are certainly not the whole story,” he said. “Given that some of these other contributors are hard to address, perhaps a case can be made for ‘doing what we can’ to reduce exposures.”
Other researchers pointed out weaknesses in the data showing a link between food dyes and children’s behavior.
Mayne said that key studies where children were randomly assigned to consume food dyes involved dosing children with multiple ingredients at the same time, which makes it difficult to determine which ingredients caused the reported behavioral changes.
Kleinman said that weaknesses of the research on food dyes and attention deficit include a lack of “rigorous criteria for defining attention deficit,” the small size of the studies, the brief period the children were followed and the difficulty of separating the effects of food colors from other factors that influence behavior, including when the children were observed and what other things they consumed.
“I think that taken as a whole, there really is very little convincing evidence that food coloring contributes to attention-deficit/hyperactivity disorder, and banning them for that reason seems to me to be out way ahead of where the evidence is right now,” Kleinman said.
Editor’s note: FactCheck.org does not accept advertising. We rely on grants and individual donations from people like you. Please consider a donation. Credit card donations may be made through our “Donate” page. If you prefer to give by check, send to: FactCheck.org, Annenberg Public Policy Center, P.O. Box 58100, Philadelphia, PA 19102.