Synthetic food colourings represent a public health toxicity risk that could be done without. These substances are added to foods (including food supplements) and drugs for the sole purpose of changing their colour.
A recent study from Masaryk University in the Czech Republic, published in Toxics (Amchova et al., 2024), provides a scientific review of toxicological research conducted over the last ten years, following the completion of the reviews conducted by EFSA. (1)
Toxicity of 14 synthetic food colors
Researchers examined the post-2024 scientific literature on 14 synthetic food dyes. However, they did not analyze one of the most suspect substances, tartrazine.
‘The overwhelming amount of data recent studies on tartrazine toxicity require more space than this review can provide,’ say the authors of the study. Here are some notes on the matter.
Tartrazine, indigestible aperitifs
Tartrazine, known as E102 or FD&C Yellow 5 or CI19140, is a synthetic lemon yellow azo colourant authorized for use in foods. It is obtained from coal tar and is soluble in water.
Tartrazine may cause intolerances and allergic reactions and is associated with the onset of hyperactivity in children (risk to be reported on the label with ‘May have an adverse effect on activity and attention in children’), as first emerged 15 years ago and subsequently reiterated. (2)
More recent studies report, in animal experiments, damage to DNA in the colon, liver and kidneys, as well as damage to the testicle and embryotoxic and teratogenic effects, harmful effects on pancreatic enzymes and a harmful action on digestion. (3)
Aperitifs and limoncello with tartrazine
In developing countries, Tartrazine is often used as a low-cost substitute for saffron, a spice that costs almost as much as gold. (4)
On our markets was instead very widespread in sugary drinks for a long time. Today it is less present, but not disappeared. It is found, for example, in the ingredient lists of drinks:
– non-alcoholic, such as Cedrata Siti sold by Lidl or the majority of alcohol-free aperitifs, as emerged from our previous market survey. (5)
– alcoholic, such as the Sunrise Rum Lime Cocktail mix sold by Lidl and the Limoncello Pallini.
14 dyes under investigation
The 14 azo dyes ‘reviewed’ by Czech researchers are themselves problematic, in many cases.
1) E104, quinoline yellow
Quinoline yellow is linked to several adverse health effects, (in primis) on children’s behavior. Its presence requires a warning on the label ‘May have an adverse effect on activity and attention in children’. It is present in various non-alcoholic drinks, such as the aforementioned aperitifs.
EFSA (2009) drastically reduced the Tolerable Daily Intake (TDI), from 10 mg to 0,5 mg/kg of body weight, noting an average exposure to this substance well above the daily threshold indicated, both for children (13,1 mg/kg) and for adults (8,1 mg/kg). (6)
A further estimate exposure to 6 of the 28 food categories where the colour E104 is authorised has led EFSA (2015) to evaluate an average daily exposure of children lower than the TDI, 0,40 mg/kg, although they remain the most exposed population group. (7)
1.1) E104, toxicity
Studies post 2014 highlight that – in addition to the influence on ADHD (attention deficit hyperactivity disorder) – quinoline yellow
– induces changes in protein conformation and the formation of protein aggregates, conditions related to Alzheimer’s and Parkinson’s
– may have the potential for endocrine disruption, resulting in hormonal imbalance
– is suspected in several studies to have a mutagenic potential. Hypothesis rejected by EFSA, but still open.
‘Overall, ongoing research on the potential health risks associated with Quinoline Yellow indicates that this topic is far from concluded and that future studies will be needed to reach a final consensus on its use as a food additive.’, conclude the authors of the study.
2) E110, sunset yellow
The orange dye Sunset Yellow FCF (E 110) is widely used in foods and drugs.
Already known as a possible source of allergy and associated with ADHD, this dye in the last 10 years, in animal studies, has been linked to
– teratogenicity (fetal damage). Zebrafish embryos exposed to the dye showed morphological deformities and increased mortality due to cell apoptosis in the cardiac region. Toxic effects on the liver and kidneys emerged in a similar experiment on chicken embryos. In the latter, another study found an interruption in the development of the immune system.
A study in human germ cells (involved in reproduction) found a mutagenic effect of exposure to 200 μg/mL of sunset yellow dye.
– genotoxicity. DNA abnormalities have emerged in meristematic cells (such as stem cells in animals) of Brassica campestris L., a plant similar to rapeseed.
Similar effects had already emerged in a study on the exposure of human lymphocytes to the dye sunset yellow, where chromosomal aberrations were highlighted.
Further confirmation comes from a study on female rats exposed for 12 weeks to the colorant sunset yellow together with the preservative sodium benzoate at doses ranging from 5 to 200 mg/kg of body weight per day.
The ADI (acceptable daily intake, or TDI) set by EFSA in 2014 is not much lower: 4 mg/kg
– hepatotoxicity. This risk emerged in a study on rats exposed for 30 days to a high dose (25-75 mg/kg/day) of a mixture of sunset yellow, tartrazine and metanil yellow, a colorant for external use, banned in food for its neurotoxic effects. Similar results emerged from the exposure of guinea pigs to 2,5 mg/kg/day of sunset yellow for 30 days
– intestinal inflammation. A dose of 2 μg/mL of Sunset Yellow altered the differentiation of small intestinal epithelial cells, with inflammatory effects. The same effect was observed in a test on guinea pigs treated with 40 mg/kg/day of dye for a week
– hematological changes. Guinea pigs exposed to a combination of sunset yellow and sodium benzoate for 12 weeks showed a decrease in hemoglobin, red blood cell count, and white blood cell count. The doses were very close to the ADIs: 5 mg/kg and 10 mg/kg for benzoate.
‘Overall, the current ADI appears to be a safe limit based on the available evidence, although higher doses may induce multiple toxic effects‘, note the authors of the study.
3) E122, azorubine, carmoisine
Red colouring E122 falls squarely among the food additives to avoid. The most recent studies highlight its toxicity at various levels.
A pro-inflammatory effect emerges in several studies. The red-orange combination of azorubine and sunset yellow (E110) tested for 30 days on rats at doses from 5 to 300 mg/kg, for example, altered the inflammatory biomarkers of the guinea pigs. (8)
A skin rash recurrent drug-induced fever is documented in a child treated with a paracetamol-based syrup containing this (useless) dye. (9)
doses of azorubine close to the ADI/TDI (4 mg/kg) caused an increase in cell apoptosis. Higher doses, however, showed a negative effect on the fertility of male mice. An experiment on zebrafish larvae then highlighted chromosomal aberrations.
‘Overall, despite the low intake as a food additive, Azorubine may pose a health problem. Therefore, its use must be carefully monitored and authorities will soon evaluate new evidence,’ conclude the authors of the study.
4) E123, amaranth red
Amaranth red E123 is the colorant of aperitifs. It is used in alcoholic beverages and non-alcoholic bitters, as well as in fish eggs.
In the United States it has been banned since 1976 due to its potential risks to human health. In the EU, however, in 2009 the ADI was reduced to 0,15 mg/kg body weight per day.
It is confirmed that this dye penetrates several organs (lungs, heart and liver, but not the brain) and fetuses. No evidence of genotoxicity or carcinogenicity was found. However, a teratogenic effect (harmful to the fetus) was found in tests on zebrafish embryos, with exposure to the substance exceeding the ADI.
‘Evaluation and control regulatory information for this colorant are necessary to assess its potential risks for consumers’, the authors of the study comment.
5) E124, Ponceau 4R, cochineal Red A
The red cochineal is strongly suspected of developmental toxicity, as well as promoting ADHD. This evidence and the high estimated consumption especially among children and adolescents have convinced EFSA to reduce the ADI for E124 from 4 mg/kg to 0,7 mg/kg of body weight. (10)
The toxicity of this dye is still a subject of research.
The mix with other additives, in animal studies, has allowed E124 to be associated with a potential mutagenic effect and alteration of the thickness of the duodenal wall.
A prenatal study on zebrafish, however, showed developmental toxicity in terms of alterations in cardiovascular function. Heart rate increased by 32% in young fish.
An allergic reaction was detected in a test on just 19 children.
An in vitro experiment finally reveals a pro-inflammatory potential of E124, particularly related to asthma.
‘Both EFSA and JECFA published their assessments more than a decade ago ; therefore, further evaluations are necessary,’ the authors of the study note.
6) E127, erythrosine, the fake red of cherries
Preserved cherries are the only food in which the use of the red colouring E127 is authorised.
Erythrosine is associated with the development of thyroid cancer cells. The evidence emerged in a study on mice, which leaves its equivalence in humans questionable. EFSA re-evaluated the substance in 2011 and set an ADI of 0,1 mg/kgbw/day. (11)
Further studies on this dye they highlight:
– potential damage to living cells in both in vitro and in vivo models at very low concentrations
– damage to testicular tissue, impairment of non-spatial memory retention as well as increased anxiety-like behavior in animal models treated with a mixture of erythrosine and tartrazine at doses exceeding the ADI
– neural tube damage in chicken embryos treated with low doses of the additive.
7) E129, allura red
The red allura ‘requires continuous monitoring’ because it can be harmful to health even at the acceptable daily intake (ADI, or TDI) established by EFSA in 2009 at 7 mg/kgbw/day.
The scientific evidence, in animal studies, associates exposure to Allura Red with:
– aberrations in liver and kidneys, after administration of the ADI dose for 4 weeks
– neurotoxicity, in terms of impairment of spatial memory
– allergies, intolerances and hypersensitivity
– triggering effect of autoimmune diseases (colitis in mice after apoptosis of intestinal epithelial cells).
It is authorized in canned red fruits, canned meat, pre-cooked shellfish, alcoholic bitters and other foods.
8) E131, patent blue
The Patent Blue may induce allergic reactions or anaphylaxis when used as a contrast medium in surgical procedures.
Used as a food coloring, however, is suspected of causing allergies. However, a clinical study with the administration of a small dose (2,5 mg) of E131 to 9 children did not confirm the suspicions.
EFSA (2013) reduced the TDI from 15 to 5 mg/kg/day, due to adverse haematological effects that occur after chronic intake of high doses.
9) E132, indigo carmine or indigotine
The colouring E132 appears safe at the acceptable daily intake (ADI) defined by EFSA as 5 mg/kg/day.
Recent studies in vitro indicate cytotoxic effects when high doses are administered.
‘There is probably a very low risk when indigo carmine is used as a food coloring; however, its possible toxicity warrants further research’, conclude the authors of the study.
10) E133, brilliant blue FCF
The TDI of the colourant E133 was confirmed by EFSA in 2010 at 6 mg/kg/day. However, at this dose some studies identify health risks.
The brilliant blue FCF appears to have cytotoxic and genotoxic potential on human blood lymphocytes (Kus et al., 2015). (12)
DNA damage in spermatozoa were induced by higher concentrations of brilliant blue (200 and 500 μg/mL). In vitro experiments finally show an increase in tumor cell growth.
Brilliant Blue is also associated with toxicity for fetal development. Furthermore, as already seen for Ponceau 4 R, in a study on zebrafish embryos it increased the heart rate by 10%.
Hematological and immune alterations also emerged at the whole-body level when rats were exposed to oral administration of 1,2 mg/kg for 90 days (the ADI is 6 mg).
11) E142, green S
The TDI of the colorant E142 has been stable at 5 mg/kg/day since 1974. However, data on genotoxicity are scarce.
The authors of the study under review found no relevant clinical, preclinical or in vitro studies to evaluate the toxicity of Green S in humans.
12) E155, brown HT
This brown dye is used without limits in the stamp printed on unprocessed meats and pre-cooked shellfish. It is also added to other foods with limits.
It doesn’t fit among the azo dyes related to ADHD. However, there are concerns that the ADI (1,5 mg/kgbw/day) may be exceeded by children and the elderly.
Studies on the toxicity of E155 (Brown HT) are scarce.
‘For this review, we found no recent clinical, preclinical or in vitro studies relevant to the evaluation of the toxicity of Brown HT in humans’, the researchers say.
13) E151, brilliant black PN
The brilliant black is considered safe at the ADI set by EFSA at 5 mg/kgbw. The Authority itself considers it unlikely that this threshold will be exceeded in all population groups.
It is employed in fish and shellfish products, as well as in dark lumpfish roe.
14) E180, litholrubine BK
The Red Lithol Rubine BK is an azo dye of petrochemical origin. It is generally used in cosmetics. Food use is limited to the coloring of edible cheese rinds.
The latest revaluation of E180 by EFSA dates back to 2010, the ADI is 1,5 mg/kgbw/day. Allergies have been reported, but no serious evidence of toxicity.
Limits based on exceeded data
At ten years old According to the latest reviews, the opinions on the toxicity of synthetic food colours, as well as the estimates of population exposure and the ADIs or TDIs – i.e. the maximum permitted doses – deserve to be updated to include new evidence, the Czech researchers stress.
Customers in the meantime, should try to reduce their consumption of synthetic dyes and protect children even from the small amounts present in sweets, snacks and other ultra-processed foods.
Marta Strinati
Footnotes
(1) Amchova P, Siska F, Ruda-Kucerova J. Food Safety and Health Concerns of Synthetic Food Colors: An Update. Toxics. 2024 Jun 27 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11280921/
(2) Marta Strinati, Dario Dongo. Synthetic food colorings aggravate neurobehavioral abnormalities in children. GIFT (Great Italian Food Trade). 25.5.21
(3) Ameur FZ, Mehedi N, Soler Rivas C, Gonzalez A, Kheroua O, Saidi D. Effect of tartrazine on digestive enzymatic activities: in vivo and in vitro studies. Toxicol Res. 2019 Nov 21;36(2):159-166. doi: 10.1007/s43188-019-00023-3. PMID: 32257928; PMCID: PMC7099100. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7099100/
(4) Dario Dongo, Alessandra Mei. Saffron, an innovative system for indoor cultivation from Israel. GIFT (Great Italian Food Trade). 18.12.22 https://
(5) Marta Strinati. Non-alcoholic aperitifs, our test on 11 products. GIFT (Great Italian Food Trade).
(6) Aguilar, F., et al. “Scientific opinion on the re-evaluation of quinoline yellow (E 104) as a food additive.” EFSA JOURNAL 1329 (2009): 1-40.
(7) European Food Safety Authority. “Refined exposure assessment for Quinoline Yellow (E 104).” EFSA Journal 13.3 (2015): 4070.
(8) Khan IS, Ali S, Dar KB, Murtaza M, Ali MN, Ganie SA, Dar SA. Toxicological analysis of synthetic dye orange red on expression of NFκB-mediated inflammatory markers in Wistar rats. Drug Chem Toxicol. 2022 Nov;45(6):2626-2636. doi: 10.1080/01480545.2021.1979579. Epub 2021 Sep 24. PMID: 34555984
(9) Panachiyil GM, Babu T., Sebastian J., Doddaiah N. A Pediatric Case Report of Fixed Drug Eruption Related to Carmoisine Colorant Present in Paracetamol Syrup. Indian J. Pharmacol. 2019;51:279–281. doi: 10.4103/ijp.IJP_29_19.
(10) EFSA Panel on Food Additives and Nutrient Sources Added to Food. “Scientific Opinion on the re‐evaluation of Ponceau 4R (E 124) as a food additive.” EFSA Journal 7.11 (2009): 1328. https://www.efsa.europa.eu/en/efsajournal/pub/1328
(11) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). “Scientific Opinion on the re‐evaluation of Erythrosine (E 127) as a food additive.” EFSA Journal 9.1 (2011): 1854. https://efsa.onlinelibrary.wiley.com/doi/abs/10.2903/j.efsa.2011.1854
(12) Kus E, Eroglu HE. Genotoxic and cytotoxic effects of Sunset Yellow and Brilliant Blue, colorant food additives, on human blood lymphocytes. Pak J Pharm Sci. 2015 Jan;28(1):227-30. PMID: 25553699.
Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".
