This link claims that above 42 degrees centigrade, the all-important ‘medicinal’ molecular structure of honey is changed irrevocably, making it indigestible and, in a sense, toxic.
Is this true?
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Surprisingly: yes, heating honey can be of a certain concern.
The article linked to above is based on ayurvedic principles which do not compare well in their reasoning with modern scientific thinking:
First, Ayurveda claims that heating honey to 104°F/ 40°C or above causes a negative chemical change that causes it to become bitter. This makes it undesirable to use from a culinary perspective in comparison with other natural sweeteners like unrefined cane sugar or fruit.
In addition, Ayurvedic dietary principles warn that consuming honey that has been cooked, baked or added to hot liquids contributes to ill health over time. The reason is because honey that is cooked becomes like glue. The molecules then tend to adhere to mucous membranes in the digestive tract producing toxins, called ama. The literal meaning of ama is undigested food or toxins stuck within the digestive tract. It is considered to be the root cause of most ill health in Ayurveda with heated honey one of the most difficult forms to detoxify.
Charaka, the ancient sage of Ayurveda, wrote over 500 years ago that “nothing is so troublesome as ama caused by the improper intake of honey.”
Dr. Krishna, an Ayurvedic practitioner for over two decades explains further that even raw honey should not be mixed with hot or spicy foods as this will by default make it “hot”. In addition, he advises against using raw honey in a hot environment where you are already warm and possibly overheated. At this point, we’ve established that the ancient system of Ayurveda considers uncooked honey to be nectar and cooked honey as poison. But, what does modern science have to say on the subject?
That is indeed an interesting question. Some concepts in the above reasoning should be regarded as very weak reasoning. It could nevertheless be accidentally right, based on empirical evidence and just getting in wrong in the pre-scientific explanation? Meanwhile, the producers of honey, have a clear message:
Is Heated Honey Toxic?
First, let’s assuage the most serious concern – no, heating honey will not turn it toxic and kill you. Heating up raw honey will change the makeup of the honey, and potentially weaken or destroy enzymes, vitamins, minerals, etc (more on this in a second) but it will not give you a horrible disease or poison you. Yes, this is something that we’re asked.
Keeping it close to raw is great for your body, but heating it isn’t going to kill you.
But that heat denatures the enzymes present in honey and destroys some vitamins should not come at a surprise. Heated protein is consumed in large amounts and the protein coming from cooked eggs or fried meat is not a concern for coctivores like humans.
What is the reason for valid concern then? A small degradation of enzymes and vitamins doesn't sound scary.
Honey and ghee are the two food substances used widely in our diet. In Ayurveda, it is quoted that heated honey and honey mixed with equal amount of ghee produce deleterious effects. […] There was a significant rise in hydroxymethyl furfuraldehyde (HMF) in 60º and 140°C heated honey samples. The browning and total antioxidant of honey mixed ghee samples was significantly higher when compared to ghee samples. […] The study revealed that the heated honey mixed with ghee produces HMF which may cause deleterious effects.
Hydroxymethylfurfural (HMF) is a by-product of thermal degradation of glucose and fructose. In this study, the effects of high HMF content of honey on biochemical parameters of rats were investigated. Experiments were conducted with 40 Wistar albino male rats, each weighing 250-350 g and covered a period of 5 weeks. The animals were divided into five groups. The first group was served as control group. HMF was injected subcutaneously at a dose of 200 mg/kg rat b.w. to the animals in group 2. Group 3 was fed with honey that contains 10 mg HMF/kg honey. In group 4 and 5, there were honeys that contain significantly high HMF content due to long storage period (181 mg HMF/kg honey) and heat process (140 mg HMF/kg honey). At the end of the feeding process, biochemical blood parameters of rats were investigated. It was observed that there were no differences among the glucose, triglyceride, HDL cholesterol, uric acid, Na, GGT, and ALP parameters of the groups. On the other hand, significant differences were observed among the cholesterol, LDL, BUN, creatinine, Ca, P, Mg, K, Cl, total bilirubin, LDH, CPK, AST, ALT, total protein, and pseudocholinesterase values of the rats. The highest adverse effects were obtained from group HMF, and it was followed by groups SH (stored honey) and HH (heated honey). It can be concluded that high HMF content of honey may affect the human health adversely; thus, HMF in honey must be controlled by beekeepers.
That is indeed a bit disconcerting. HMF is present in honey from the start and increases with age as well as with the application of heat. This substance is suspected to be a carcinogenic agent. But how much of this substance actually forms in the intended application of honey as sweetener in tea?
The effect of heating at various temperatures (30, 40, 50, 60, 70 and 80 °C) on dynamic viscosity, colour, 5-hydroxymethylfurfural (5-HMF) concentration and diastase activity of raw rape honey were assessed. […] Heating for 15 min between 50 °C and 80 °C did not significantly degrade the quality of the honey, but, slightly enhanced formation of 5-HMF and reduced the diastase activity.
Heating honey may not be ideal, and it does spoil a little over time. In relation to the question it has to be noted that all hexose saccharides, and especially fructose as found in table sugar, can degrade in the same way.
All of this has to be put into perspective: a table spoon of honey in a cup of tea will not reach a high enough temperature for long enough to really become so toxic in a meaningful dose to be of any real concern in that regard.