How honey becomes toxic?

22.01.2019. 11:00

We have all heard about the benefits of including honey in our diet. Honey is full of minerals, vitamins, antioxidants, enzymes, sugars, and amino acids. Ancient civilizations even praised it. Switching from refined sugar to honey is a step that many take in order to improve their health and diet.

Modern science has confirmed the health benefits of consuming honey, especially raw honey. Here you can learn about the difference between regular and raw honey. However, have you heard about honey toxicity? Yes, we were as shocked as you are. In this article, we will explore the reasoning behind that statement and if it is true.  

How honey becomes toxic?

It is always recommended to look for raw (unheated) honey to reap the maximum benefits, and to avoid pasteurized (heated) honey. However, many of us use honey in baking, cooking, and put it in hot liquids such as tea or coffee.

Do you know what that does to honey? You guessed right, by heating the honey you pasteurize it. You make it just the thing you wanted to avoid; you might have made your honey toxic. Heating honey causes negative chemical changes which can contribute to bad health, especially to the digestive system. Information about the negative effects of heated honey can even be found in Ayurveda, a system of traditional diet and holistic healing.

Heated honey in Ayurveda

In Ayurveda honey is regarded as essential food and medicine. It is also considered the only acceptable sweetener for people trying to lose weight because it stimulates metabolism, while other sweeteners have the opposite effect.

Ayurveda recommends taking a cup of warm water with a bit of raw honey as the first thing in the morning. Doing that should stimulate metabolism throughout the day.

Even though honey is recommended because of many benefits, Ayurveda advises against heating honey for health-related and practical reasons. Ayurveda claims that heating honey to 40°C (104°F) or higher causes a negative chemical reaction which gives the honey a bitter taste.

Moreover, it claims that consumption of heated honey contributes to bad health over time. That might explain why honey toxic after heating belief might exist. The reasoning is that heated honey becomes like glue which sticks to the mucous membranes in the digestive tract and releases toxins.

What science says about honey toxicity?

Science confirms that heating honey changes it because heat eliminates many of its beneficial effects. The most noticeable change of heating honey is a loss of probiotics and enzymes.

There was research in 2010 which tested physicochemical characteristics and chemical constituents of heated honey and honey mixed with ghee.

The researchers evaluated the effect of consuming heated honey, ghee, honey mixed with ghee, and heated honey mixed with heated ghee. The test subjects were rats. The most problematic finding was that at only 60°C (140°F) there was a significant rise in hydroxymethyl furfuraldehyde, commonly known as HMF. HMF is derived from dehydration of certain sugars, which means that it is formed in early stages of caramelization. When the heated honey was mixed with ghee, the negative effects were more prominent. Such a result lead the researchers to conclude that the increase in HMF may act as a poison.

However, after rats have been fed a mixture of raw and heated honey with ghee, they have not shown a significant change in weight gain, food intake, and relative organ weights. Other research suggests that HMF may be toxic and carcinogenic in humans, but more research is needed. As a result of potential danger, many countries impose restrictions on maximum levels of HMF in beverages and food.

Bees don’t react well to heated honey

There is nothing unusual about bees eating honey as it is their winter food, but something happens when the honey is heated. Beekeepers who gave their bees heated honey have noticed that it can be deadly.

The reason for the bad effect of heated honey is probably due to the increase of HMF which might be toxic to bees. When you consider such honey toxic from heat effect, that makes you wonder what effect it has on humans, right?

A similar pattern can be observed when calves are fed pasteurized (heated) milk instead of raw milk. Calves fed pasteurized milk are underdeveloped, sick, and suffer organ damage which can result in death before they even reach adulthood.

Some beekeepers give their bees high-fructose corn syrup when they want their colonies to be quickly ready for pollination season, but they might be doing them more harm than good.  The HMF is the main reason why high-fructose corn syrup is not good for bees. Researchers have found that by heating corn syrup the levels of HMF rise, especially at temperatures higher than 48°C (120°F). Also, HMF levels rise with time so older corn syrup has more HMF than newer syrup.

The problem with HMF levels in corn syrup rising with heat is that the temperature inside the hive can be high enough to produce HMF. Unfortunately, bees won't hesitate to feast on the syrup if given to them even though it has a negative effect on bees. It is a responsibility of every beekeeper to take proper care of their bees. If you don’t have honey from your apiary to give to your bees it would be better to provide them with plain old sugar made into syrup.

Heat effects on honey

Note that the following effects of heating honey are based on heating raw honey, not honey that you can buy in your local grocery store. By observing what happens to honey under heat, we can try to determine is honey toxic.

#Antibacterial and antioxidant activity of honey

The factors responsible for antibacterial action in honey are hydrogen peroxide activity and non-peroxide activity. Peroxide activity of honey is affected by storage, light, and heat. Unfortunately, that means that if you buy raw honey which was kept in improper conditions you could lose up to 86% of peroxide ability to fight microbes.

Here it is important to mention Maillard reaction, a chemical reaction between an amino acid and a reducing sugar which usually requires heat (specifically heat above 140°C (285°F)). Many colors and flavors from food come from Maillard reactions. Some examples of that are browning of the bread into toast, caramel made from sugar and milk, the color of beer, etc. The Maillard reaction should not be confused with caramelization which is only pyrolysis of sugar.

Processing honey at high temperatures or prolonged storage trigger the Maillard reaction and recent studies have shown that antibacterial and antioxidant activities depend on the stages of the Maillard reaction. At the intermediate stage honey’s antibacterial activity is increased, but in the advanced stage it is decreased.

Previously mentioned HMF is a substance that appears in the initial stages of Maillard reactions because of dehydration of sugars, such as glucose and fructose, in the presence of amino acids. Low quantities of this substance are naturally found in foods containing sugar, such as caramel products, dried fruit, bread, instant coffee. Usually, fresh honey has a low amount of HMF (less than 17 HMF/kg of honey) but if heated at the temperature of 100±10°C HMF content increases to  330mg/kg of honey.

#Enzyme content

In 2000 R.C.Sharma published “Honey: processing and product development” where he explains that heating honey at 90°C for 8 hours pretty much destroys enzymes. Such prolonged heat, among others effects, causes changes in carbohydrates and destroys antimicrobial properties.

#Vitamins and minerals

Minerals are usually resistant to heat, but their content still decreases. The only mineral present in honey which resists heat is magnesium.

A study from 2011 showed that the bioavailability of minerals can be affected by Maillard products because they are able to interfere with mineral solubility. Also, a negative influence on phosphorus absorption was observed in male adolescents who had a diet rich with Maillard products.


A big impact of heat applied to honey is destruction or reduced bioavailability of essential amino acids which results in protein nutritional impairment. A study from 2002 showed that some amino acids are reduced by 50%, a significant impact.

Katrina Brudzynski went through an experiment in 2013 which revealed that storing honey for six months reduced protein content by 46.7%. The greatest drop in protein content happened during the first three months.

Heated honey toxic to bees, but what about us?

Based on the evidence we have shown seems that heated honey is entirely different food from honey in a raw state. However, keep in mind that you probably wouldn’t make your honey toxic unless it’s heated too much or for too long. So far scientists are still not sure what effect might heated honey have on a human body.

Until more research has been done, we can only speculate on possible negative effects. If you don’t want to possibly make honey toxic by using it in cooking, baking, or hot drinks you can substitute it with another natural sweetener such as maple syrup.

Consuming honey occasionally probably won't have any negative effect on your health, so you don’t have to avoid honey completely. However, if you are a daily consumer of honey, we would recommend that you try to avoid heating honey past 40°C (104°F).