Which foods have formaldehyde in them naturally?

January 12, 2026 •

4 min read

Trace amounts of formaldehyde occur naturally in living organisms, including the plants and animals we consume. Understanding which foods have formaldehyde is key to separating natural occurrences from illegal or industrial contamination, which is a major food safety concern in certain regions. This naturally present chemical is typically found at low, non-toxic levels and can even be reduced through proper food preparation.

Quick Summary

Formaldehyde is present naturally in trace amounts in many foods, including fresh fruit, vegetables, meat, and seafood. These low, naturally occurring levels are generally not a health concern. However, improper food preservation or industrial processes can add higher, potentially harmful concentrations. Factors like freezing and cooking can influence its levels.

Key Points

Natural Presence: Formaldehyde occurs naturally in many foods as a byproduct of metabolic processes.
Common Food Sources: Fruits (apples, bananas), vegetables (carrots, mushrooms), meat, and seafood are known to contain trace amounts.
Illegal Additive: In some regions, industrial formaldehyde (formalin) is illegally added to foods like fish to extend shelf life.
Effect of Storage: Freezing and cold storage can increase natural formaldehyde levels in some marine fish and crustaceans.
Cooking Reduces Levels: Formaldehyde is water-soluble and can dissipate with heat. Washing, soaking, and cooking food properly can help reduce its content.
Low Risk from Natural Levels: The low concentrations of natural formaldehyde found in food are not considered a health risk for most people.
Avoidance of Added Chemicals: Buying from reliable retailers and choosing fresh or unprocessed foods helps avoid exposure to illegally added preservatives.

Formaldehyde: A Naturally Occurring Chemical in Your Food

Formaldehyde is a naturally occurring chemical compound with the formula CH$_2$O. It is a product of metabolic processes in most living organisms, including plants, animals, and humans. As a result, it is a normal component of many foods we eat daily. The presence of formaldehyde in food can come from two main sources: natural metabolic processes or, in rare cases, as an illegal additive used as a preservative. For most consumers, the natural levels of formaldehyde in a balanced diet pose no health risk.

Which Fruits and Vegetables Have Formaldehyde?

Many fruits and vegetables contain naturally occurring formaldehyde as part of their metabolic breakdown. The concentration can vary depending on the specific food item, its age, and its ripeness. Some common examples include:

Fruits: Apples, bananas, pears, grapes, plums, and mangoes. Studies have shown pears to have higher levels, sometimes up to 60 mg/kg.
Vegetables: Carrots, cabbage, cauliflower, mushrooms, spinach, and tomatoes. Dried shiitake mushrooms, in particular, can contain significantly higher natural levels compared to raw ones.
Dried foods: Reconstituting dried foods, such as dried mushrooms, can help reduce the formaldehyde content, as it is water-soluble.

Formaldehyde in Meat and Seafood

Formaldehyde is a byproduct of metabolism and breakdown processes in both animals and fish. For example, in many marine and freshwater fish, a chemical called trimethylamine oxide (TMAO) breaks down into formaldehyde and dimethylamine after the organism dies. This breakdown is accelerated during frozen storage, causing formaldehyde to accumulate over time.

Seafood: Some fish, like Bombay duck, can naturally accumulate high levels of formaldehyde during cold storage, with levels reaching up to 400 mg/kg. Shrimp, squid, and cod also contain trace amounts.
Meat and Poultry: Fresh beef and poultry also contain low, naturally occurring levels of formaldehyde. The amounts typically found are considered safe and are much lower than in certain types of seafood.

Formaldehyde in Processed Foods and Beverages

While naturally present levels are generally low, some processing methods can either add formaldehyde or increase its concentration. Illegal practices, though monitored, can be a concern in certain regions.

Artificial Sweeteners: Aspartame, when broken down in acidic conditions, can release formaldehyde.
Smoked Meats: Cooking and smoking meats at high temperatures can generate volatile organic compounds, including formaldehyde.
Commercial Milk: Studies have found some commercial UHT and powdered milk products contain higher formaldehyde concentrations than fresh milk, potentially from processing, preservation, or packaging.

The Difference: Naturally Occurring vs. Added Formaldehyde

It is crucial to distinguish between naturally occurring, low-level formaldehyde and the potentially harmful, illegally added form. Regulating bodies like the European Food Safety Authority (EFSA) and the World Health Organization (WHO) have established guidelines for safe oral exposure levels, recognizing that natural dietary intake is not a health risk. However, the use of industrial-grade formaldehyde, or formalin, as a food preservative is strictly prohibited in most countries due to its toxicity.

Comparison of Formaldehyde Sources


Feature	Naturally Occurring Formaldehyde	Illegally Added Formaldehyde (Formin)
Source	Produced via natural metabolic processes in plants and animals.	Deliberately added as a preservative to extend shelf life.
Levels	Generally very low and non-toxic.	Can be present in higher, potentially harmful concentrations.
Health Risk	Not associated with adverse health effects at typical dietary levels.	Ingestion of high concentrations can cause severe health issues.
Regulatory Status	Not regulated as an additive since it's naturally present.	Its use in food is strictly prohibited in most countries.
Detection	Background levels can make detection of illegal addition difficult without analyzing related compounds.	Often detectable through lab tests and can sometimes be correlated with other chemical byproducts.

Reducing Formaldehyde in Food

While the natural levels are safe, consumers can take simple steps to minimize their intake, especially when dealing with processed or stored foods.

Tips for Reducing Formaldehyde:

Thorough Washing: As formaldehyde is water-soluble, washing fresh fruits and vegetables thoroughly can help remove surface traces.
Soaking Dried Goods: For dried products like mushrooms or vermicelli, soaking them in water and then discarding the water before cooking can be effective.
Proper Cooking: Heat can help dissipate formaldehyde from food. Cooking meats and fish thoroughly to the recommended internal temperature is a simple step.
Balanced Diet: Maintaining a balanced diet and avoiding over-reliance on a small range of processed foods helps to prevent excessive intake of any single chemical.

Conclusion

The presence of formaldehyde in various foods is a natural phenomenon resulting from the metabolic processes of living organisms. From fresh fruits and vegetables like apples and carrots to protein sources like meat and fish, trace amounts are common and generally harmless. However, it is important to distinguish this from the illegal and dangerous practice of using formaldehyde as a preservative in certain food items. By understanding which foods have formaldehyde and practicing proper food preparation, consumers can focus on eating a balanced diet while minimizing exposure to unnecessary chemicals.

This article is for informational purposes only and should not be considered medical advice. For further reading on food safety regulations, you can refer to the European Food Safety Authority (EFSA) guidelines.

Frequently Asked Questions

No, the low, naturally occurring levels of formaldehyde found in many foods are generally not considered dangerous. The human body naturally produces and metabolizes formaldehyde, and the amount from a typical diet is well within safe limits established by health organizations like the WHO.

Pears and apples are two examples of fruits with relatively significant levels of naturally occurring formaldehyde. According to studies, concentrations can vary, but these are part of the natural metabolic breakdown of the fruit.

Yes, cooking can help reduce formaldehyde levels. As the chemical is water-soluble and volatile with heat, methods like washing, soaking, and cooking food thoroughly can help to dissipate or remove it.

In some marine and freshwater fish, a naturally occurring chemical called trimethylamine oxide (TMAO) breaks down after death, producing formaldehyde. This accumulation is more pronounced during frozen storage and in certain species like Bombay duck.

It can be difficult to tell without laboratory testing, as it's naturally present. However, some signs in fish include unusually stiff flesh or a lack of the typical fishy odor, though relying on reputable sellers is the best prevention.

Some processed foods, like smoked meats or certain powdered milk products, can show higher levels due to processing or packaging methods. The breakdown of artificial sweeteners like aspartame can also release it.

Yes, it is perfectly safe. Consuming foods with naturally occurring formaldehyde is not a health risk. Your body's natural processes effectively manage these low levels, and a balanced diet ensures no excessive intake from any single source.

Dried shiitake mushrooms can contain higher concentrations of formaldehyde compared to their raw counterparts. Soaking them thoroughly before cooking is recommended to reduce this content.