IS HEATED HONEY TOXIC?

When I hear particularly strong statements like “heated honey becomes toxic,” something immediately triggers my critical thinking. Honey is mainly made of fructose and glucose, just like sugar, so if heated honey became toxic, then sugar should be toxic too.

The other day, after reading yet another message saying “be careful Elena, heated honey becomes toxic,” I decided to look into the issue more deeply.

There are many myths in nutrition. Beyond understanding whether they are true or not, I also like to understand where they come from. This myth about honey dates back around 2,000 years.

WHERE THE MYTH COMES FROM

“In Ayurveda, Charaka stated that heated honey and honey mixed in equal parts with ghee produce harmful effects in the body and may even cause death.” (1)

Charaka was an Indian physician and scholar who made a significant contribution to the field of Ayurveda. Ayurveda is a traditional system of medicine that originated in the Indian subcontinent. Charaka lived between 100 AD and 200 AD.

As much as I respect Ayurveda, it is still knowledge that dates back 2,000 years, and I believe it is not possible to ignore the scientific understanding humanity has gained since then.

This study (1) was carried out specifically to verify Charaka’s claims about the toxicity of honey and ghee.

When honey is heated, there is a significant increase in HMF (we will explain what this is shortly), both in raw and processed honey. The difference in the amount of HMF produced at 60°C and at 140°C is not very large. What is particularly interesting is the increase in total phenolic compounds and flavonoids in honey heated to 140°C. Antioxidant activity increases as honey is heated. But wait, wasn’t heated honey supposed to be toxic? As for honey and ghee, in this case too both HMF and antioxidants increase. So honey and ghee together are not a problem.

LET’S LOOK AT THE DETAILS

Honey does not become toxic when heated, however at temperatures of 45°C, 55°C and 65°C the antibacterial activity of honey is inhibited (2). Therefore, heating honey can compromise its ability to fight bacterial infections. On the other hand, prolonged heating at higher temperatures (50°C, 60°C and 70°C) can increase antioxidant activity (3). In addition, heating honey can induce the secretion of granulocyte colony-stimulating factor (G-CSF), which helps strengthen the immune system (3,4).

To be precise, higher temperatures can have a negative effect on enzymes naturally present in honey, such as glucose oxidase, which plays a role in its topical antibacterial action. However, this impact is largely irrelevant for internal use, as stomach acid will inactivate these enzymes anyway, regardless of temperature (6).

Important: the main therapeutic properties of honey are attributed to its polyphenol content. Polyphenols increase with temperature. This means we can safely add honey to hot drinks or use it for cakes, biscuits and other baked goods. There is absolutely no problem, on the contrary, its antioxidant power increases.

NUTRIENTS IN HONEY (7)

Macronutrients
The carbohydrate content ranges from 60 to 95% of its dry weight and includes mono-, di- and trisaccharides. The floral source plays a key role in determining this ratio. More than 20 different carbohydrates have been identified in honey. The main carbohydrate is fructose (28–40%), followed by glucose (20–35%), while disaccharides and trisaccharides account for about 5% and 1% respectively. Nerd note: the most commonly identified disaccharides are maltose, maltulose, turanose, sucrose and nigerose, while some trisaccharides such as erlose, centose, isomaltotriose, panose, psopanose and ketose are found in small amounts.

Protein content generally ranges from 0.2% to 0.5%, mainly in the form of enzymes and free amino acids. Total free amino acids range between 10 and 200 mg per 100 g of honey, with proline accounting for about 50% of the total.

Lipid content in most honey samples is negligible, around 0.002%. Plants and beeswax mainly contribute to the presence of lipid compounds such as palmitic, oleic, myristic and linoleic acids.

Micronutrients
The mineral and vitamin profile of honey varies depending on floral type and geographical origin and represents about 0.2–0.5% of its dry weight. Potassium and sodium account for about 80% of total minerals, while iron, copper and manganese are present in smaller amounts.

As for vitamins, studies have identified thiamine, riboflavin, pyridoxine, niacin and ascorbic acid in different honey samples, although in amounts that do not meet daily recommended intakes.

Enzymes
As for vitamins, studies have identified thiamine, riboflavin, pyridoxine, niacin and ascorbic acid in different honey samples, although in amounts that do not meet daily recommended intakes.

Polyphenols
Polyphenols in honey are believed to derive from plant nectar. Their quality and quantity depend on geographical area, floral source, climate conditions and bee species.

Polyphenols have attracted significant scientific interest as preventive agents against degenerative and chronic inflammatory diseases. The main therapeutic activities of honey are attributed to its polyphenol content, as they are the most abundant phytocompounds.

Honey polyphenols have high bioavailability compared to other foods due to the absence of
a complex food matrix and
the lack of food interactions.

Contaminants
Honey may contain contaminants such as pesticides, antibiotics, heavy metals and other toxic substances, which can be introduced accidentally through environmental exposure or beekeeping practices.

Pathogenic contamination by Clostridium botulinum has been considered a risk, especially for children under 12 months of age. For this reason, honey should be sterilized using gamma irradiation to reduce infection risk without losing its natural therapeutic properties.

WHAT IS HMF? (8)
HMF, or hydroxymethylfurfural, is a sugar dehydration product. It can form in foods containing sugars, especially after heating or cooking. Its formation has been widely studied because HMF was once considered potentially carcinogenic for humans. However, to date, toxicity results have been negative.

HMF is virtually absent in fresh foods but forms naturally in sugar-containing foods during thermal processes such as drying or baking. Along with other compounds responsible for flavor and color, HMF forms during the Maillard reaction and caramelization. It also forms slowly during storage. Acidic conditions favor HMF formation. HMF is a well-known component of baked goods. During bread toasting, levels increase from 14.8 mg/kg after 5 minutes to 2024.8 mg/kg after 60 minutes. It also forms during coffee roasting, reaching up to 769 mg/kg.

HMF is found in low amounts in honey, fruit juices and UHT milk. In these foods, as well as in vinegars, jams, alcoholic beverages and biscuits, HMF can be used as an indicator of excessive heat treatment. Fresh honey contains less than 15 mg/kg of HMF, depending on pH, temperature and age. Codex Alimentarius standards require honey to contain less than 40 mg/kg of HMF, except for tropical honeys, which must remain below 80 mg/kg.

Much higher levels of HMF are naturally found in coffee and dried fruit. Roasted coffee can contain between 300 and 2900 mg/kg of HMF, while dried plums may contain up to 2200 mg/kg. Dark beer contains around 13.3 mg/kg, while baked goods range between 4.1 and 151 mg/kg.

HMF levels vary widely depending on production technology and storage conditions. To assess dietary intake, consumption patterns must be considered. Coffee is the most relevant source, both in terms of HMF levels and amounts consumed.

HMF IN HONEY (9)
HMF forms from the decomposition of fructose in acidic conditions. Heat increases the rate of this reaction exponentially as temperature rises. HMF is naturally present in most honeys and usually increases with aging and heat treatment. Its accumulation varies depending on honey type.

It is important to note that HMF is not harmful at the levels found in foods. Many sugary products, such as jams and molasses, contain HMF levels 10 to 100 times higher than those found in honey.

Fresh, natural honey can show variable HMF levels, typically below 1 mg/kg, but these increase rapidly at ambient temperatures above 20°C. It is worth noting that temperatures inside a beehive can exceed 40°C during summer months, when honey production is at its peak. HMF in freshly extracted honey is usually below 10 mg/kg. Higher levels may indicate excessive heating during extraction.

Many countries set maximum limits for HMF. In the European Union, the maximum allowed level for table honey is 40 mg/kg.

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