Red 40, Yellow 5, and Friends

Red 40, Yellow 5, Yellow 6, Blue 1, Blue 2, Green 3 — these are all synthetic food dyes originally derived from petroleum. They're cheap, vibrant, and stable, which is why they show up in cereal, candy, sports drinks, and pickles.

The research that put dyes on the map: a 2007 Lancet study by McCann et al. found that mixtures of common artificial food colors and sodium benzoate increased hyperactive behavior in 3-year-old and 8/9-year-old children in the general population ^[1].

In response, the European Union now requires foods containing certain dyes (Yellow 5, Yellow 6, Red 40, and others) to carry the warning: 'May have an adverse effect on activity and attention in children' ^[2]. The FDA has not required the same warning in the U.S. — they consider these dyes safe at typical exposure levels ^[3], though they acknowledge some children may be sensitive.

A 2021 California Office of Environmental Health Hazard Assessment (OEHHA) report — a comprehensive review of the evidence — concluded that synthetic food dyes can cause neurobehavioral effects in some children, and that current acceptable daily intake values may be too high to protect sensitive kids ^[4].

If you're trying to limit them: skip brightly-colored processed foods, or look for products colored with beet juice, turmeric, paprika, or annatto instead.