Food manufacturers know only too well that you “eat with your eyes.” And if a food product looks a little dowdy, it’s unlikely to fly off the shelves.
To remedy this potential blockage in their revenue stream, many turn to artificial food colorants.
In brief, food dyes are usually petroleum-based chemicals that color your food.
And they’re everywhere. From gaudy ice cream to supernaturally bright orange peel, dyes are increasingly difficult to avoid.
Food dyes are broadly split into “artificial” and “natural.” As the name suggests, some dyes come from natural sources, like paprika and beet juice.
But artificial dyes are the most widely used because they tend to provide brighter hues and last longer.
This article will focus on artificial dyes because that’s where the bulk of the controversy is.
But first, a quick trip into the past.
Nothing new under the sun
Humans have added color-changing chemicals to foods for hundreds of years.
For example, back in 1782, in The Experienced English Housekeeper, Elizabeth Raffald recommended using copper salts to make pickled vegetables more appealingly green.
Today, many people worry about the effects of artificial colors on health, and this, too, is nothing new.
In 1820, Frederick Accum published a popular book, the name of which requires its own paragraph:
Treatise on the Adulteration of Food and Culinary Poisons, Exhibiting the Fraudulent Sophistications of Bread, Beer, Wine, Spirituous Liquors, Tea, Coffee, Cream, Confectionery, Vinegar, Mustard, Pepper, Cheese, Olive Oil, Pickles, and Other Articles Employed in Domestic Economy and Methods of Detecting Them.
The title alone shows that, even back then, food colorants were widespread, and the public was wary.
Food dyes today
Manufacturers have tried out a range of food dyes over the decades. Today, in the United States, the country's Food and Drug Administration (FDA) has the final say on whether a food dye is safe.
Currently, they have approved nine artificial dyes for use in foods:
Food, Drug, and Cosmetic (FD&C) Blue No. 1 — also called brilliant blue, acid blue 9, and E133
FD&C Blue No. 2 — also called indigo carmine and E132
FD&C Green No. 3 — also called Fast Green FCF, Food Green 3, Green 1724, Solid Green FCF, C.I. 42053, and E143
Orange B — remarkably, this may be its only moniker
Citrus Red No. 2 — also called C.I. Solvent Red 80 and C.I. 12156
FD&C Red No. 3 — also called erythrosine
FD&C Red No. 40 — also called Allura Red and E129
FD&C Yellow No. 5 — also called tartrazine, E102, and C.I. 19140
FD&C Yellow No. 6 — also called Sunset Yellow, Orange Yellow S, and C.I. 15985
In Europe, it’s the European Food Safety Authority (EFSA) that makes the decisions.
Of the nine dyes above, the following three are banned in the European Union:
FD&C Green No. 3
Citrus Red No. 2
But the EFSA permits the use of some artificial colors that aren’t used in the U.S., including:
Quinoline Yellow WS — E104
Carmoisine — E122
Ponceau 4R — E124
Patent Blue V — E131
Green S — E142
Brilliant Black BN — E151
Brown HT — E155
For readers in the U.S., the E numbers above are shorthand codes for food additives in the E.U.
Food dyes and health
There’s no straightforward answer to, “Are food dyes bad for you?” This is a complex topic.
The fact that the FDA or EFSA has signed off on a food additive provides some reassurance. But not everyone is convinced that the available evidence is strong enough to prove that these dyes are safe.
For instance, the Center for Science and the Public Interest (CSPI) published a damning report in 2010.
In Food Dyes: A Rainbow of Risks, the authors explain:
“Almost all the toxicological studies on dyes were commissioned, conducted, and analyzed by the chemical industry and academic consultants. Ideally, dyes (and other regulated chemicals) would be tested by independent researchers.”
“Furthermore,” they continue, “virtually all the studies tested individual dyes, whereas many foods and diets contain mixtures of dyes (and other ingredients) that might lead to additive or synergistic effects.”
In other words, we all consume a cocktail of chemicals each day, so it’s hard to know whether research on one dye in isolation is meaningful. And the troubles don’t end there.
More problems with the evidence
According to the CSPI report, current studies into artificial colors don’t go far enough.
They explain that studies are too short — humans consume these chemicals for a lifetime, but a study rarely lasts longer than 2 years.
All of these studies are performed in animals, too, bringing its own challenges — not everything that happens in a rat will happen in you. However, there wouldn’t be an ethical way to run these studies in humans.
Another issue is that this research doesn’t always include pregnant animals, so we can’t see how dyes might affect unborn offspring.
Also, the FDA permits food dyes to contain around 10% impurities.
This means that there are often other chemicals in food dyes, including 4-aminobiphenyl, 4-aminoazobenzene, and benzidine, which are known cancer-causing compounds.
And in studies investigating food colorants, these impurities wouldn’t be present. So, they’re not getting tested.
Finally, researchers never test the effect of these chemicals on the gut microbes of animals or humans.
And we know from recent clinical studies that similar chemicals, such as emulsifiers and artificial sweeteners, can adversely impact gut microbes.
Keeping all this in mind, we'll now briefly cover some of the most famous debates about food dyes.
Do they cause cancer?
All currently approved food colorants have been through testing to assess whether they increase the risk of cancer.
The FDA has set a limit for cancer-causing food colors. The limits are supposed to ensure that they cause no more than 1 case of cancer per 1 million people.
But, as the CSPI notes, they set these limits based on usage in the 1990s. Today, we consume 50% more of these colorants than we did then.
Each currently approved colorant has been tested multiple times, generally in mice or rats.
Some artificial food dyes don’t seem to cause cancer, but others might. And most of the research was done decades ago.
We haven’t got the space to outline them all, but we’ll mention Blue No. 2, as there was some evidence that it increased cancer risk.
Manufacturers use this dye in foods like ice cream, candy, snacks, and cereals.
A note on 1 person per 1 million
It’s worth taking a step back to think about this logic. The FDA is saying that the price of more colorful food is that up to 1 person in 1 million can develop cancer.
Sure, that’s a rare event, but if that one person is you, then the other 999,999 cancer-free people are of little comfort.
When you remember that we’re talking about additives with no nutritional value and no benefit beyond their color — even 1 in 1 million might be too much of a risk.
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A study from 1985 found that at high doses, Blue No. 2 was associated with brain tumors in rats.
However, the authors concluded that the “statistically significant increase in gliomas in the high-dose male rats was not found to be biologically significant.”
This was because the findings weren’t consistent with various criteria required to classify a chemical as cancer-causing.
Although the FDA approved this food dye, not all experts agreed with the decision.
The CSPI report quotes Dr. Benjamin A. Jackson, from the Division of Pathology in the Color and Cosmetics Evaluation Branch of the FDA.
He said, “The possibility cannot be outrightly excluded that the compound (Blue No. 2) itself, its metabolite(s), or a secondary effect induced by the high dose of the color may have acted to increase the number of brain tumors seen in this study.”
Along similar lines, cancer specialist Dr. William Lijinsky, from the National Cancer Institute, said, “The incidence of these (brain) tumors in the high-dose group versus the controls is highly significant.”
He continued: “In my own laboratory, this would be considered prima facie evidence of carcinogenicity of a treatment. This is especially so because this tumor is so rare, and my conclusion is that Blue No. 2 is a carcinogen and should be regulated accordingly.”
Although other studies didn’t find any links between Blue No. 2 and cancer, one has to ask whether it’s worth the risk. Do we need to feed blue food to our kids?
Hyperactivity in kids
In the 1970s, scientists spotted links between artificial colors and attention deficit hyperactivity disorder (ADHD) in children. Some people believed that these compounds might even cause ADHD.
However, later studies and updated analyses didn’t identify such a strong or convincing effect but concluded that some children with ADHD might be sensitive to food dyes.
Other researchers still believe that artificial colors may influence children’s behavior, whether they have an ADHD diagnosis or not.
And some scientists think that certain children might be more genetically susceptible to food dyes.
The fact that some might be susceptible while others aren’t could help explain why studies haven’t consistently demonstrated an effect.
The EFSA also has some concerns about some food dyes used in the U.S. Yellow No. 6 is a fairly common food colorant in the country. For instance, it gives Fanta its electric hue.
It’s not banned in the E.U., but if manufacturers there use Yellow No. 6, they have to state on labeling that it “may have an adverse effect on activity and attention in children.”
The same goes for another five food colorants in the E.U. — Yellow No. 5, Quinoline Yellow WS, Carmoisine, Ponceau 4R, and Red No.40.
Like most things humans eat, food dyes can cause allergic reactions in some people.
For instance, in a 1978 study, researchers recruited 56 people who had been to a hospital due to an allergic condition.
They then tested whether the participants had allergic responses to food dyes. Below are the percentages of participants who responded to specific dyes:
Yellow No. 5: 11%
Yellow No. 6: 17%
Red No. 40: 16%
Red No. 2: 9%
Ponceau 4 R: 15%
Red No.3: 12%
Blue No. 1: 14%
Meanwhile, other studies have found that Yellow No. 5 causes allergic reactions in people with aspirin allergy, asthma, an allergic skin condition called urticaria, and other allergic conditions.
The four dyes most likely to cause reactions are Blue No. 1, Red No. 40, Yellow No. 5, and Yellow No. 6.
Although reactions are generally mild, we have to remember that we're often exposed to a cocktail of these chemicals daily.
And there isn’t any research about the effects of a combination of food dyes over a lifetime.
Inflammatory bowel disease
A mouse study from 2022 investigated links between the food dye Red No. 40 and inflammatory bowel disease (IBD).
The two most common forms of IBD are colitis and Crohn’s disease.
The research showed that ongoing exposure to Red No. 40 at the levels we often experience made colitis worse in mice with the condition.
On the other hand, intermittent exposure to the food dye didn’t increase colitis risk.
However, exposure to this food dye in early life increased the rodents' susceptibility to colitis later in life.
This might be important because food manufacturers often use dyes to make food appealing to children.
This research certainly doesn’t prove that Red No. 40 has the same effect in humans. And the authors of the study call for more research.
Gut bacteria: A quick note
Over the past couple of decades, research into gut bacteria has exploded. As a result, experts now know that our miniature onboard guests play important roles in health and disease.
Some scientists have asked whether food dyes interact with our gut bacteria in a meaningful way.
Given that there are hundreds of species in your gut, it’s perhaps unsurprising that some can metabolize — or break down — food dyes. But what does this mean for your health?
A review from 2012 focused on azo dyes, the most commonly manufactured type. Azo dyes include Red No. 40, Citrus Red No. 2, Yellow No. 5, and Yellow No. 6.
The authors conclude that although some of these food colorants might not cause cancer, some of the compounds produced when gut bacteria metabolize these dyes might.
Because everyone’s microbiome is different, and not all strains of bacteria can break down these dyes, this might help explain why studies on food dyes and cancer have conflicting results.
This is a very new field of research, but it’s an important line of investigation.
The takehome message
Although scientists have studied the potential effects of food dyes on health, many studies are decades old.
Plus, they’re almost exclusively conducted in animals, and experts don’t always agree about how to interpret the results.
And, of course, we’re all different — we’re likely to respond to different chemicals in different ways.
So, despite dyes having been in our diets for centuries, there are still questions.
Overall, we have to ask whether we need our food to be so bright or whether we can manage with less lurid snacks.
The FDA and EFSA have approved the dyes that they think are safe. But not all experts agree that these chemicals are risk-free, as they haven't all been tested with modern methods.
And because all they do is brighten foods, it seems like an unnecessary gamble.
According to the CSPI, since 1955, the amount of food dyes consumed in the U.S. has increased five-fold.
In Europe, there's a slow shift toward using natural colors, but the U.S. is lagging behind.
Avoiding food dyes can be challenging. But by focusing on unprocessed or minimally processed foods, you can avoid the vast majority of them. And you’ll likely have a healthier diet, too.
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