The Right Chemistry: The colourful history of food dyes


As early as 1500 BC, Homer in his Iliad described the use of saffron prepared from the stigma of the Crocus sativus flower to colour food.

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Do they affect children’s behaviour? Are they carcinogenic? Should they be banned? Those are questions that have been raised about a family of chemicals commonly referred to as “food dyes.” There are some contentious issues here to be sure. But one aspect of these additives is not contentious. They have a colourful history!

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As early as 1500 BC, Homer in his Iliad described the use of saffron prepared from the stigma of the Crocus sativus flower to colour food, a practice also adopted by the ancient Egyptians. Since the Egyptians were very familiar with numerous mineral pigments, such as iron and lead oxides, and also knew how to extract red dyes from madder root or the crushed bodies of kermes insects, it is likely that some of these colourants found their way into food.

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It wasn’t until the Middle Ages that the first controversy about food colouring cropped up. Bread made from refined white flour came to be favoured over coarse, dark bread because it looked to be more “pure.” White bread was more expensive to produce, so some bakers took the short route and added chalk (calcium carbonate) or lime (calcium oxide) to dark bread to lighten it. This did not go down well with King Edward I (1272-1307) who introduced the first law dealing with food adulteration. “If any default shall be found in the bread of a baker,” the king decreed, “let him be put upon the pillory and remain there at least one hour in the day.”

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Nevertheless, profits from the whitening of bread were seductive enough for the prospect of being pilloried for an hour not to be enough of a deterrent. The public was blissfully unaware of being deceived until 1820 when German chemist Friedrich Accum who had settled in England published his Treatise on Adulteration of Food and Culinary Poisons. By this time, bakers had expanded their repertoire and were also adding alum (potassium aluminum sulphate) to bread, but they were not the only ones to engage in adulteration. Milk was commonly tinged yellow with lead chromate, and candy makers coloured their sweets with copper, mercury and lead compounds. Accum went as far as publishing the names of those selling the toxic products, but his exposé was drowned out by a public smear campaign against him organized by the adulteraters.

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A new twist in the thread of the history of food dyes, one that would lead to controversies that dominate to this day, was the discovery in 1856 of the first synthetic dye by William Henry Perkin. Prior to Perkin’s accidental discovery of mauve in a futile quest to synthesize quinine, anyone wishing to colour food was forced to rely on nature’s palette. The key to Perkin’s synthesis was the use of aniline derived from coal tar, a waste product of the production of coal gas and coke. Chemists were quick to capitalize, and soon produced a whole range of “coal-tar colours” that were embraced by the food industry since they were cheap to produce, were free of the acute toxicity of metal salts, and produced vibrant colours with very small doses. By the turn of the century, some 80 synthetic dyes were used to colour food in a totally unregulated fashion.

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Then came a pivotal moment. Harvey Wiley was appointed chief of the Bureau of Chemistry at the U.S. Department of Agriculture, the forerunner of the Food and Drug Administration. Wiley was disturbed by the lack of regulations with respect to substances added to food and became a champion of reform. He was the force behind the passage of the 1906 Pure Food and Drug Act that for the first time imposed criminal penalties on selling “adulterated” food. Dyes were of particular concern because of their ability to conceal damage and make inferior foods more appealing. Wiley commissioned a study of the food dyes being used and concluded that only seven of these were safe. Over the years, some of these were eliminated and others were added as more and more research came to light. The difficulty of establishing safety is highlighted by the different lists of approved colour additives in Europe, Canada and the United States

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Red dye No. 2, also known as “amaranth,” was one of the synthetic dyes approved by Wiley and became a favourite of the food industry. Then in the 1950s, the first sign of trouble appeared when a study reported breast tumours in female rats fed the dye. In response, the FDA ordered followup studies in rats and mice. The results were not corroborated, but then came word that a couple of Russian studies had found intestinal tumours in rats. Even though experts judged these to be of poor quality and unreliable, FDA ordered another test on rats that seemed to indicate an increase in tumours in females. Critics claimed the experiment had been bungled, but still, enough confusion had been created for FDA to remove Red No. 2 from the market. Although this dye was never used by M&Ms, the company decided to remove the red candies out of concern that the public would choose to avoid all red dyes. This triggered a ridiculous conspiracy meme that the red M&Ms had aphrodisiac properties and that workers were stealing them for their nocturnal pleasures.

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A current concern is about another red dye, this time Red No. 3, or “erythrosine,” also one that was originally approved by Harvey Wiley, and consequently the 1906 legislation. It was also approved “provisionally” in cosmetics until the 1990s, when studies showed that rats fed large doses developed thyroid tumours. This caused the dye to be then banned from cosmetics, but curiously it was allowed in foods because of a quirkiness in FDA procedures that makes it difficult to ban a substance that is on a “permanently,” rather than a “provisionally,” approved list.

The Center for Science in the Public Interest (CSPI) in the United States has filed a petition with FDA to initiate procedures to ban Red No. 3 because of the cancer connection. CSPI also points out, correctly, that accumulating evidence affirms that synthetic dyes can cause behavioural problems in some children and suggests replacement by natural dyes derived from the likes of paprika, cabbage, turmeric and beets. Many companies are already doing this, which is commendable since synthetic dyes serve only a cosmetic purpose. So, why take any chance, even if the evidence of risk is inconclusive? Avoiding dyed foods is not a bad idea in any case, given that dyes are usually found in processed foods of questionable nutritional quality. Maybe seeing red when it comes to synthetic reds is justified.

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Joe Schwarcz is director of McGill University’s Office for Science & Society ( He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.


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