What are the Side Effects of E172 Food Additive?

January 9, 2026 •

4 min read

While E172, a common food coloring derived from iron oxides, is largely considered safe for human consumption within regulated limits, scientific bodies have identified some areas of concern. Primarily used to add color to a variety of foods, the safety of E172 has been under re-evaluation, especially regarding the presence of nanoscale particles and potential contaminants.

Quick Summary

This article discusses the current understanding of E172 food additive safety, exploring potential side effects, the role of nanoparticles, regulatory considerations, and recent re-evaluations of iron oxide pigments. It details the minimal risks for most consumers versus potential dangers of excessive intake.

Key Points

Low Absorption: Iron oxides (E172) are generally not absorbed by the intestinal tract in significant amounts, with most being excreted from the body.
Nanoparticle Concerns: Research indicates that E172 may contain nanoparticles, which could be absorbed more readily and have potential cytotoxic effects on cells, though this area requires more study.
Contamination Risk: Some sources suggest E172 may be contaminated with other metals, like aluminum, which is linked to its own health concerns, although maximum limits are set by regulators.
Safety Re-evaluation: EFSA has previously noted a lack of sufficient toxicological data for a complete safety assessment of E172, particularly concerning nanoparticle effects.
Excessive Iron Overload: The primary risk from iron comes from excessive intake of supplements, not from E172 food coloring, which can lead to serious health issues like hemochromatosis.
Minimizing Exposure: Reducing consumption of processed foods that rely on artificial colorants like E172 is a practical way for concerned individuals to limit their intake.

What is E172 and How is it Used in Food?

E172 is the European Union's designation for a group of food colorants known as iron oxides and iron hydroxides. These mineral-based pigments come in various shades, including black (E172(i)), red (E172(ii)), and yellow (E172(iii)), which can be used alone or mixed to create orange and brown tones. Historically derived from natural sources, the versions used in industrial food production today are synthetically produced from iron powder to ensure purity and consistency.

Iron oxides are prized for their stability, including their resistance to heat and light, making them ideal for a wide range of applications. You can find E172 in the coatings of many products, including:

Meat pastes and processed meats
Confectionery, desserts, and cake packets
Cheese rinds and sausage casings
Colored pastas
Black olives, which are often green olives artificially colored

Regulation and Safety Assessments of E172

Regulatory bodies worldwide, such as the European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA), have long considered E172 safe for use as a food additive within specified maximum levels. However, assessments are ongoing as new research emerges, particularly concerning nanoscale components. For example, a 2015 EFSA re-evaluation concluded that an adequate safety assessment was not possible due to a lack of sufficient toxicological data, especially concerning genotoxicity and reproductive effects of iron oxide nanoparticles.

Are There Side Effects of E172 Food Additive? A Closer Look at the Research

For the average consumer ingesting E172 within regulated limits, evidence of harmful side effects is scarce. The iron compounds are generally not absorbed by the intestinal mucosa and are mostly excreted. However, several potential issues have been flagged by recent research and regulatory concerns.

Nanoparticle Absorption and Cellular Effects

One of the most significant modern concerns surrounding E172 involves the presence of nanoparticles, which are significantly smaller and may behave differently in the body than larger particles. Studies have shown that iron oxide nanoparticles can cross the gastrointestinal barrier more effectively than larger forms, potentially leading to absorption and deposition in organs. A study on human neuroblastoma cells found that nanoscale E172 could induce moderate cytotoxicity and cell death, though this was an in-vitro study and its direct implications for human health are still under investigation.

Oxidative Stress: Research suggests that the toxicity of iron oxide nanoparticles may be mediated by oxidative stress and mitochondrial dysfunction in cells, potentially caused by the generation of reactive oxygen species.
Intestinal Permeability: The ability of nanoparticles to permeate the intestinal barrier could potentially impact gut health and overall systemic effects, though more research is needed to understand the long-term impact on the microbiome.

Potential Contaminants

Some forms of E172 may contain contaminants like aluminum, which could have its own associated health risks. Research suggests aluminum may influence female sex hormones, potentially impairing reproductive function, and could disrupt the gut microbiome and immune system. Concerns have also been raised about other toxic elements, such as cadmium and lead, which could be present as impurities, necessitating revised maximum limits.

Comparison: Risks of E172 (Iron Oxide) vs. Excessive Iron Overload


Aspect	E172 (as a Food Additive)	Excessive Iron Overload (from Supplements/Diet)
Source	Synthetically produced iron oxides for coloring purposes.	High intake of iron from supplements or iron-rich foods.
Absorption	Generally poorly absorbed by the intestinal tract.	Readily absorbed, potentially leading to systemic buildup.
Acute Risks	Negligible risk in regulated food doses. Inhalation of industrial dust is a different matter.	Can cause severe gastrointestinal distress, vomiting, diarrhea, and abdominal pain.
Chronic Risks	Primarily related to nanoparticle effects or contaminants; long-term studies are limited.	Can lead to hemochromatosis, with risks of liver damage, heart problems, and diabetes.
Risk Group	Potential concerns for individuals with high exposure or specific sensitivities.	High risk for children with accidental overdose and individuals with genetic predispositions.

What the Consumer Should Know

For most people, the consumption of E172 within legal limits is unlikely to cause adverse effects, particularly given its low absorption rate. However, individuals seeking to minimize their exposure can reduce their intake of highly processed foods and seek out products with "cleaner" labels. Given the recent re-evaluations and inconclusive data on nanoparticles, a cautious approach is warranted, particularly for vulnerable populations like children.

For those interested in cleaner eating, a great resource is the Environmental Working Group (EWG) [https://www.ewg.org/foodscores/explore-ingredients/].

Conclusion: A Nuanced View on E172

While many health and safety organizations consider E172 to be safe when consumed in regulated amounts, the scientific landscape is evolving. Concerns regarding the nanoscale particles within the additive and potential impurities like aluminum have prompted further investigation by regulatory bodies like EFSA. While the risk of acute side effects from food consumption is minimal for most adults, individuals concerned about long-term or unknown effects may choose to limit their intake of heavily processed foods containing E172. Ultimately, staying informed about food additives and making conscious dietary choices is the most proactive approach to personal health.

Frequently Asked Questions

E172 is the food additive designation for iron oxides and iron hydroxides, which are used as mineral-based coloring agents.

While iron oxides occur naturally, the E172 used in food production is typically synthesized from iron powder to ensure consistency and purity.

Yes, E172 is generally considered safe for consumption by regulatory bodies like the FDA and EFSA when used within regulated limits.

E172 is used in a wide range of processed foods, including meat and fish pastes, confectionery, desserts, and artificially colored items like some black olives and cheese rinds.

The primary modern concerns relate to potential health effects of nanoscale particles within the additive and the possibility of contamination with other heavy metals.

E172 is largely not absorbed by the intestines and is unlikely to cause direct digestive issues for most people; concerns about gut microbiome changes are theoretical and related to potential contaminants.

To avoid E172, it is best to reduce the consumption of highly processed and artificially colored foods and to check ingredient labels for the specific E-number or 'iron oxides'.