Is HMF in Honey Toxic to Humans? A Deeper Look at the Facts

December 28, 2025 •

4 min read

According to the Codex Alimentarius Commission, the maximum permitted level of HMF in most honeys is 40 mg/kg, suggesting that at normal concentrations, the compound is not considered a significant health threat to humans. Despite this, concerns about the safety of hydroxymethylfurfural (HMF) in honey persist, fueled by misleading information about heating honey and potential toxicity.

Quick Summary

Hydroxymethylfurfural (HMF) naturally forms in honey during storage and heating, serving as a quality indicator. The compound is not inherently toxic in the low concentrations found in properly stored and processed honey. Studies on HMF's potential negative effects are often based on extremely high doses or indirect metabolic byproducts in animal models, not typical human consumption from honey.

Key Points

HMF is a natural compound: Hydroxymethylfurfural (HMF) forms naturally in honey from the breakdown of sugars, especially fructose, when exposed to heat or stored for a long time.
Not a health risk at normal levels: The low levels of HMF typically found in commercially available honey do not pose a toxic risk to humans.
HMF is a quality indicator: The concentration of HMF in honey is primarily used as an indicator of freshness and to detect overheating or improper storage.
Human metabolism neutralizes HMF: The human body efficiently metabolizes and excretes HMF, preventing the accumulation of its potentially harmful byproducts.
Higher HMF in other foods: Many other common food items, like roasted coffee, baked goods, and dried fruits, contain far higher concentrations of HMF than honey, which are consumed without concern.
Storage affects HMF levels: Storing honey at high temperatures or for extended periods will increase its HMF content.

What is HMF and Why Does It Form in Honey?

Hydroxymethylfurfural (HMF) is an organic compound that develops naturally in carbohydrate-rich foods, including honey. It is a result of the degradation of fructose and glucose—the primary sugars in honey—in an acidic environment, particularly when exposed to heat or stored for extended periods. This process is part of the Maillard reaction, which is also responsible for browning and flavor changes in many cooked foods.

Fresh honey contains little to no HMF. Therefore, its presence and quantity serve as a reliable indicator of the honey’s history, signaling if it has been overheated during processing, improperly stored at high temperatures, or aged for a long time.

Factors Influencing HMF Levels in Honey

The concentration of HMF in honey is a dynamic value influenced by several key factors:

Heat Treatment: The higher the temperature and the longer the heating duration, the faster HMF forms. Overheating, often done to prevent crystallization or to filter honey, can significantly elevate HMF levels.
Storage Temperature and Duration: Storing honey at higher temperatures accelerates the chemical reactions that produce HMF. Honeys stored at room temperature (20-25°C) for a year can show drastically increased HMF concentrations compared to those stored at cooler temperatures (4-5°C).
Floral Source: The specific floral origin of honey can influence its pH and sugar composition, which in turn affects the rate of HMF formation. Some varieties may naturally produce HMF faster than others.
pH and Acidity: The acidic nature of honey acts as a catalyst for HMF production. Honeys with lower pH values can contribute to faster HMF formation.

The Misconception of HMF Toxicity from Honey

The claim that heated honey becomes toxic is a widespread myth. Concerns about HMF toxicity are often based on out-of-context or misconstrued scientific findings. While HMF has shown some mutagenic and genotoxic effects in in vitro (cell culture) or high-dose animal studies, these conditions do not reflect normal human consumption of honey. The key distinction lies in the concentration and metabolism of HMF.

HMF Toxicity in Animal vs. Human Metabolism

Research shows that HMF is readily absorbed through the human digestive tract and efficiently metabolized into different compounds that are then excreted in the urine within 24 to 48 hours. However, some animal studies show that HMF can be converted into a different metabolite, 5-sulfoxymethylfurfural (SMF), which is not as easily excreted and is considered a genotoxic agent. Crucially, research has shown that this conversion does not seem to happen in humans to a significant degree, meaning the genotoxic metabolite does not accumulate.

Comparison Table: HMF in Honey vs. Other Foods


Food Item	Typical HMF Levels (mg/kg)	Context and Comments
Fresh Honey	Typically < 15	Very low levels, indicating fresh product.
European Standard Honey	≤ 40	A regulatory quality standard, not a toxicity limit.
Tropical Honey	≤ 80	Acknowledges faster natural HMF formation in warmer climates.
Toast/Baked Goods	Up to 180	HMF forms readily during baking; part of the browning process.
Roasted Coffee	Up to 2900 or more	A major source of dietary HMF; significantly higher than honey.
Dried Fruits (e.g., prunes)	Up to 240+	HMF forms during dehydration and long storage.

The table clearly demonstrates that HMF levels in everyday processed foods like coffee and bread can far exceed the regulatory maximum for honey, yet these foods are consumed safely. The international standard for honey quality (Codex Alimentarius) sets the HMF limit to ensure freshness and proper handling, not because typical levels pose a toxic risk to humans.

The Dual Nature of HMF: Adverse and Beneficial Effects

It's important to recognize the nuance in the scientific community's understanding of HMF, which includes both potential adverse effects at high concentrations and some reported beneficial properties.

Potential Detrimental Effects (at high concentrations):

Organotoxicity: High concentrations have shown cytotoxic effects on certain cells in lab settings.
Genotoxicity: Conversion into the metabolite SMF has shown genotoxic potential in animal models, though this conversion is minimal in humans.

Potential Beneficial Effects (at lower concentrations):

Antioxidant Properties: Studies have shown HMF can act as an antioxidant, helping to protect cells from damage caused by free radicals.
Anti-inflammatory Effects: Research has indicated HMF may possess anti-inflammatory properties.
Anti-allergic Effects: Some studies suggest HMF could have anti-allergic potential by inhibiting the release of certain compounds involved in allergic reactions.

Conclusion: Navigating the HMF Issue with Knowledge

The fear surrounding HMF toxicity in honey is largely misplaced and based on a misunderstanding of how the compound is formed, its typical concentrations, and how the human body processes it. While high concentrations of HMF have shown adverse effects in specific laboratory settings, the levels found in properly handled and stored honey are well within safe limits established by international food safety bodies like the Codex Alimentarius Commission. The average person is exposed to significantly higher levels of HMF from everyday foods like coffee, bread, and dried fruits without ill effect.

Ultimately, HMF serves as a valuable quality indicator for honey. By understanding what influences its levels—namely heat and storage duration—consumers can make informed choices. To minimize HMF intake and enjoy the freshest, highest-quality honey, simply buy from reputable sources and store your honey in a cool, dark place. The idea that honey becomes toxic when heated is a myth that deserves to be dispelled by these scientific facts.

Authoritative Source

For a comprehensive review of the toxicology and health effects of HMF, one can consult the review article published in BMC Chemistry.

Frequently Asked Questions

No, the notion that heating honey makes it toxic is a myth. Heating honey does increase its HMF content, but the resulting levels are still well within the safe range for human consumption, especially when compared to other common foods.

Yes, HMF is safe to consume at the levels typically found in food. It is found in many heat-processed foods, including coffee, bread, and caramel. Most concerns about HMF toxicity are based on studies using extremely high doses in laboratory animals, which do not reflect dietary intake.

International standards set by the Codex Alimentarius Commission generally limit HMF content in most honey to 40 mg/kg. For honeys from tropical regions, where heat exposure is more likely, the limit is often set higher at 80 mg/kg.

HMF is a quality parameter because its concentration directly indicates how much a honey has been subjected to heat and prolonged storage. Low HMF levels signal freshness and careful handling, while high levels suggest the honey is older or was overheated during processing.

Fresh, raw honey typically has very low to non-detectable levels of HMF. Over time, however, even raw honey will naturally develop HMF, though at a slower rate than honey that has been heat-treated.

Scientific studies have investigated and identified some potential beneficial properties of HMF at lower concentrations, including antioxidative, anti-inflammatory, and anti-allergic effects. However, these are often observed in preclinical settings and more research is needed.

To minimize HMF intake from honey, purchase honey from reputable sources that emphasize fresh and minimally processed products. Store honey in a cool, dark place to slow the natural formation of HMF over time.