Ep 28: Do Synthetic Colors Give You Cancer or ADHD?

We've talked about gold and green on this podcast. We promised a red episode. And after digging into the history of red dyes, as well as all of the panic around them, we decided that red deserved its own episode.

First: what even is a dye?

A dye is basically a molecule that's sticky. It binds to surfaces, and when light hits it, it vibrates at a frequency our eyes register as color. Humans have been doing this for centuries; dyeing textiles, making paint, coloring food, and using pigments in cosmetics. Most early dyes came from nature, from plants like turmeric, paprika, saffron, annatto. Big overlap with spices, which... is a whole other rabbit hole.

Here's the thing though: natural dyes were often scarce, expensive, and tied up in global trade routes controlled by wealthy Europeans. By the late 1800s, those resources were being used up at unsustainable rates, so something had to give.

Enter: synthetic dyes (and coal tar, unfortunately)

Before we had electricity, coal was used for energy. After it burned, it left behind a sticky black tar residue. Scientists started extracting things from it, including a super reactive chemical called aniline, which turned out to be a precursor to basically everything.

The first synthetic dye was reportedly made by accident by an 18-year-old British chemist who was trying to synthesize a malaria drug. He ended up with a vibrant purple goop instead. It was called mauvine (or "aniline purple"), it swept across Europe, and within a few years chemists had synthetic coal tar dyes in every color of the rainbow.

Those dyes quickly made their way from textiles into food. Manufacturers loved them because they were potent, stayed vibrant, and made food look more appealing for longer. But the starting materials for many of these colorants were, to put it lightly, not great. It was lead, arsenic, mercury - the usual suspects.

By 1906, the Pure Food and Drugs Act was signed, and the approved list of food colorants dropped from around 80 down to 7.

The Halloween incident of 1950

A candy company made "Spooky Lozenges" containing 1-2% synthetic Orange 1 dye (and now we know that 1-2% is a LOT OF DYE). Kids ate them and got really sick. Because of this, the FDA launched an investigation and by 1960 gained full jurisdiction over all color additives.

At this point the Delaney Clause was also enacted, which basically giving the FDA authority to pull any colorant shown to cause cancer in humans or animals (we're gonna go on the record and say we think that's a good thing). All colorants on the market were labeled "provisionally listed", essentially meaning 'we're looking into it, stay tuned.'

Red 2 and the beginning of red dye panic

In 1971, a Soviet study linked Red 2 to cancer via a poorly-done rat study. Red dyes were in everything at this point, because red makes food look fresh and appetizing - especially meat, which loses color fast once an animal is no longer alive. Consumers pushed hard for a ban thanks to the study. The FDA said there wasn't enough evidence and kept it in use, even while running their own rat studies with similar findings. Red 2 was finally banned in the US in 1976.

There was a lot of fallout over their decision. Public trust in red food coloring tanked so hard that M&Ms removed the red color entirely, even though Red 2 had never been used as their colorant. It was an innocent bystander! Red didn't make a return to the M&M bag for a decade.

So what's the deal with Red 40?

Red 40 largely replaced Red 2 after the ban, and it's still used today. But somewhere along the way, the conversation shifted from "does this cause cancer" to "does this cause hyperactivity in children."

That link was originally proposed in 1973 by Dr. Benjamin Feingold at the American Medical Association, who suggested hyperactivity in young children was connected to certain food additives. However, his dietary intervention was later disproven. Studies from Southampton University in 2004 and 2007 found that food dyes mixed with the preservative sodium benzoate increased hyperactivity in children ages 3 and 8-9. California research in 2021 claimed a positive link as well.

It's important to remember, though, that those studies tend to leave out a pretty significant variable: foods containing Red 40 also tend to contain a lot of sugar. Plus, these studies weren't done well at all, but the public latched onto the results regardless.

Red 3: the one that actually got banned

Red 3 (Erythrosine) has been in use since 1906. Around 1990, a study fed rats a diet of 4% Red 3 for 30 months and found increased thyroid tumors. And like, it's not really a stretch to say that if your diet contained a whole 4% of a food dye for over 2 years, it could be linked to some negative effects. Europe restricted it significantly, and the US banned it for use in cosmetics, topical drugs, and some foods. The US recently moved to ban it more broadly and still cited the cancer research as their reference.

Our personal take

Eating something and putting it on your skin are very different things. The data linking synthetic colorants to harmful effects is almost entirely from ingestion studies, often at very high concentrations. That doesn't mean cosmetic colorants get a free pass forever, since historically they haven't always been safe, but it's worth being specific about what the evidence actually shows.

Do artificial dyes need to be in food? Probably not. There could be some validity to the cancer studies, and dyes aren't really necessary since the benefit is purely aesthetic. But the hyperactivity argument is a lot messier than the headlines make it sound, and pretending like those two things are the same doesn't help anyone.

It's also important to remember that even when a finished product is safe for consumers, the people manufacturing the raw ingredients may have very different exposure levels. We have precautions, but they aren't the same.

So overall, you're probably going to be fine if you eat Cheeto's or Skittles once in a while, just be mindful of how much you're consuming and make sure your diet is balanced overall.

Bibliography

• The Federal Food, Drug, and Cosmetic Act (FD&C Act)

• Feingold, B.F. (1973). Presented at the annual meeting of the American Medical Association.

• McCann, D. et al. (2007). Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community: a randomised, double-blinded, placebo-controlled trial. The Lancet, 370(9598).

• FDA Color Additives History: fda.gov/industry/color-additives/color-additives-history