What makes ice cream so colorful? Food colorings have a bad reputation—not always rightly so.

It's hot. Very hot, in fact. Anyone who buys an ice cream to cool off can marvel at its sheer colorful variety: the wonderful world of food coloring.

Bright green mint ice cream can be found there, as can unnaturally blue Smurf ice cream, which usually tastes just as artificially like "bubblegum." The latter owes its color not to real gnomes with pointed hats, but to synthetic dyes like "Patent Blue V" (E 131). Things get even more colorful outside of fancy gelaterias in the "ice lolly" market segment.

Colorings aren't just found in many ice creams and sweets for kids. They also add color to aperitifs for adults. For an evening refreshment, the Aperol Spritz, for example, remains as popular as ever; it's vibrant thanks to E 110 (Orange Yellow FCF) and E 124 (Cochineal Red A). The more intense red of Campari's competitor is created from a mixture of E 102 ( Tartrazine ), E 122 ( Azorubine ), and E 133 ( Brilliant Blue FCF ). The food industry doesn't skimp on colorings in other areas, too, from strawberry yogurt and baked goods to bright orange salmon substitutes.

However, many consumers and even some experts are suspicious of this colorful activity: Food colorings, especially artificial ones, have a negative reputation due to health concerns. Some of the approximately 40 substances approved in Switzerland and the EU could trigger cancer and allergies, they say. The promotion of hyperactive behavior in children is also being discussed. And in the USA, Secretary of Health Robert F. Kennedy has declared war on food colorings, as if they were the real cause of the poor health of many Americans.

The often overly bright colors apparently fulfill a human need. "Color is the most important product-specific sensory cue in determining people's expectations regarding the likely taste and aroma of food and beverages," says Oxford psychologist Charles Spence, summarizing their effect in a review article .

The power of these expectations is demonstrated by a classic experiment conducted by American researchers: They gave test subjects sugar water that always tasted of cherry flavor, but which they sometimes colored red, sometimes orange, and sometimes green. While the testers always correctly identified the flavor of the red drink, one in five believed they also tasted orange in the orange version. With the green drink, a quarter of the test subjects incorrectly guessed the flavor of lime.

German-speaking participants would probably have been more likely to think of woodruff. This shows that our color and taste expectations are often shaped less by the colors and aromas of natural examples than by culturally acquired associations. The industry has recognized that eating is a visual experience. No wonder they're trying to play to this trope.

And this has been the case ever since: Even the ancient Egyptians used the golden-yellow coloring saffron to make food look more appetizing; in South America, the red dye carmine, extracted from cactus scale insects, was known from a similarly early stage. It can still be found today as E 120 in sweets, beverages, and sausages, as well as in lipstick and other red cosmetics. This isn't just a concern for vegans, as real carmine is still made from these insects. Even those allergic to carmine sometimes react severely to the substance.

This disproves two common misconceptions about the health effects of food colorings. One is the notion that natural substances are automatically harmless. The other is the assumption that substances with an E number are always synthetic (and therefore automatically more harmful; see the first misconception).

In fact, E numbers are assigned to all types of food additives—substances that serve to improve the shelf life, taste, texture, or appearance of food. The "E" stands for "Europe," because the now internationally used system was introduced by the European Economic Community in 1962. The numbers 100 to 180 are reserved for colorants.

These can be roughly divided into three categories: natural, nature-identical, and synthetic. Natural colors include the red pigment lycopene (E 160 d), which comes from tomato peels, and the carotenoids that give carrots their color (E 160a). Such natural substances can often be reproduced more easily and cheaply using organic chemistry—in which case they are considered "nature-identical." Finally, synthetic colors were developed entirely in the chemical laboratory and usually have no counterpart in nature.

The negative reputation of such substances can partly be understood in light of recent history: Starting in the mid-19th century, the fledgling chemical industry developed numerous dyes, primarily for textiles. Following the motto "What could possibly go wrong?", these dyes soon also began to beautify food.

The resulting, initially largely unregulated, color craze also included the use of natural but toxic minerals such as red lead oxide and mercury sulfide (cinnabar). This only changed after several spectacular series of deaths. Great Britain and Germany enacted the first legal regulations towards the end of the 19th century, and the USA followed a few years later.

Today, synthetic colorings are strictly regulated in industrialized countries. "If colorings are approved for use in food, they pose no risk to human health, provided they are used in accordance with the requirements of the Food Additives Ordinance," explains the Federal Food Safety and Veterinary Office (FSVO) with a solemn statement.

Consumer advocates' concerns remain regarding the remaining 40 or so approved colorings. How justified are they? The devil is in the details. This starts with the permissible daily intake (RDI) in milligrams per kilogram of body weight, which is considered safe and should not be exceeded with normal consumption.

"It's difficult to realistically estimate such intake levels in real life," says Lothar Aicher, a chemist at the Swiss Center for Applied Human Toxicology, which is affiliated with the universities of Basel, Geneva, and Lausanne. However, the biggest problem in assessing the risk of potential health effects is the often insufficient data from studies.

Example of behavioral problems caused by synthetic azo dyes: The suspicion essentially goes back to a study conducted by the University of Southampton in 2007. In this study, three- and eight-year-old children showed slightly increased hyperactive behavior when they consumed a drink containing six synthetic azo dyes every day for six weeks.

Experts and the European Food Safety Authority (EFSA) struggled to evaluate the results due to the study's limited effect and methodological weaknesses: An initial EFSA opinion in 2008 concluded that there was insufficient evidence to suspect a potential risk. Since 2010, despite little change in the data, the authority has required the warning "May impair activity and attention in children" on products containing one of the incriminated "Southampton Six" dyes.

Some azo dyes are also suspected of being carcinogenic. "When broken down by bacteria in the intestines, certain amines can actually form, which in turn are suspected of causing cancer," says Aicher. However, the evidence for the currently approved dyes in this group is uncertain: "There are indications. And the discussion is ongoing. But the data is still very contradictory."

However, in the case of colorings, the so-called precautionary principle applies, i.e., the rule "In case of doubt, err on the side of the accused," says Aicher. "After all, food colorings are primarily a marketing tool." And for most of the colorings, no matter how slightly suspect, there are safer alternatives.

The toxicologist certainly believes it's worth taking a closer look. But he also warns against excessive concern: "When it comes to Aperol Spritz, you should definitely first consider your alcohol and sugar consumption. The evidence for harmful effects is pretty clear."

An article from the « NZZ am Sonntag »