The internet is full of podcasts that spread misinformation on health-related topics, such as food dyes and vaccines. The internet also provides the resources to discover the truth, which is usually far more nuanced and interesting. Robert F. Kennedy, Jr, the secretary of the Department of Health and Human Services, plans to order the U.S. food industry to eliminate many food dyes within the next two years based on virtually no clinical evidence linking them to health risks in humans.
Let’s consider the evidence regarding the most common food dyes currently used by the U.S. food industry. First, it’s important to keep in mind the words of Paracelsus, a Swiss physician and alchemist from the Renaissance, who warned that “the dose makes the poison.” Food dyes are very large molecules that carry considerable electrical charges. This makes it hard for them to traverse membranes, especially the ones that protect the brain. This molecular feature also underlies why studies that claim toxicity have involved administering very large doses of the dyes.
FD&C Blue No. 1, also known as Brilliant Blue FCF, is commonly used in popsicles, soft drinks, Jell-O, cake icings, and sometimes even canned peas, is very poorly absorbed from the gastrointestinal tract. Virtually all of the ingested dye is not absorbed and is discarded in feces. Brilliant blue FCF is one of the oldest FDA-approved color additives, having been permanently listed for use in food and ingested drugs in 1969. It is considered nontoxic and safe for consumption. The molecular size of this dye is so large that it is not able to cross the blood-brain barrier. There is no known impact of Brilliant Blue on the brain.
FD&C Green No. 3, because of its large molecular size, is also poorly absorbed by the intestines. Its use as a food dye is prohibited in the European Union and some other countries. In the United States, Fast Green FCF is the least used of the main FDA-approved dyes. The World Health Organization concluded that it has low toxicity and is not carcinogenic. There were no health concerns with consumption, and it is not able to cross the blood-brain barrier.
FD&C Red No. 3 is known as erythrosine. It’s an organic compound that contains iodine. In January 2025, the outgoing Biden administration started the process to ban Red No. 3 in all foods and ingested drugs. The decision to ban Red No. 3 was based on a study in which male rats developed thyroid tumors after being exposed to high levels of the substance. Other later studies in humans and animals failed to show similar results. In truth, carcinogenicity only occurs with extremely high doses. The federal Center for Food Safety and Applied Nutrition and Cancer Assessment Committee concluded that the risk of developing cancer in humans is unlikely at the low erythrosine levels consumed as a food color. In early 2025, Health Canada stated that erythrosine “does not pose a health risk to the general Canadian population at the levels set out in the List of Permitted Food Colours.”
Erythrosine can cross the blood-brain barrier. Studies in rats using exceptionally high doses (equivalent to a single 2000 mg oral dose!) reduced motor activity and altered serotonergic and dopaminergic activity in some brain regions. In contrast, lower dosages in the same study had no effect on motor activity or brain chemistry. In another highly preliminary study only involving six young female rats per group, erythrosine dose dependently disrupted the normal histopathology of the brain and suppressed antioxidative and acetylcholinesterase enzymatic activity.
FD&C Yellow No. 5, known as tartrazine, is a commonly used coloring agent all over the world, in products like butter, cheese, and ice cream. There are claims that tartrazine can cause ADHD-like behavior in children. Although it is conceivable that certain foods may act as a trigger in children who are genetically predisposed, the evidence for this effect is weak. There are also rumors that tartrazine consumption (specifically its use in Mountain Dew) can impair male erectile function, as well as testicle and penis size. These claims have been disproved. Tartrazine is only harmful at extremely high dosages. The amount of tartrazine in food is strictly controlled. In fact, despite online rumors that Yellow No. 5 has been banned in Europe for being toxic, the dose allowed in Europe, where it is called E102, is higher than in the United States: 7.5 milligrams per kilogram of body weight per day as compared to 5. It can cross the blood-brain barrier. A preliminary study in rats found that an extremely high dose (equivalent to 35,000 mg!) increased the latency time in the passive avoidance test of memory. Another rodent study found that low-dose levels of tartrazine produced no adverse effects in learning and memory functions.
In summary, food dyes are like all chemicals in our diet: The dose determines the poison. (For more about the effects of foods on the brain, click here.) Animals fed large doses show toxicity; in contrast, animals fed low doses that mimic those consumed by humans show no toxicity. There is no scientifically valid reason for removing these dyes. However, except for the aesthetics of the food we eat, there is no reason that they should be in our food, either.