Since 2015, the European Commission has been on the trail of adulterated honeys. Now, Europe is studying banning a sweetener made from Chinese-sourced honeys due to its grayanotoxin content, the toxic component of so-called “crazy honeys”. In high doses it affects the central nervous system and produces confusion, agitation, delirium and amnesia. It can also cause a cholinergic syndrome whose effects, very similar to those produced by ingesting the fly swatter mushroom Amanita muscaria, have been well known for thousands of years.
Honey made by honey bees from European species such as Rhododendron luteum and R. ponticum (known as rhododendrons or azaleas) has been used more than once during wartime. Gauls, Lombards, Saxons and Britons placed beehives with toxic honey along the roads that Roman soldiers passed. Some, after consuming the sweet and seemingly innocuous food in excess, were knocked out by sudden colic.
The poisonous honey from around Trebizond (Turkey) was famous in the time of Pliny, who gave an account of it in his Natural History (XXI: XLV: 77). In his Geography (12.3.18), Strabo narrates how the heptacomites, "absolutely savage peoples" who "inhabited the Turkish mountains and lived perched on trees and assaulted walkers", ended more than two thousand years ago with three maniples (almost five hundred soldiers) of Pompey's army. They did this by placing bowls of crazy honey on the roads. Later, "when the soldiers drank the mixture and lost consciousness, they attacked and eliminated them easily."
More famous is the episode of poisoning suffered by the Greek mercenaries (the Expedition of Ten Thousand) who, almost 25 centuries ago, invaded Persia recruited by Cyrus the Younger. In the Anabasis (Book IV: 16), Xenophon, who was part of the expedition as a general, related the effects that the ingestion of R. ponticum honey had produced on the expeditionaries:
“What was most astonishing was seeing the many hives that were there. And all the soldiers who ate from the combs had their souls turned, and they threw up and down, and none of them could stand. Those who ate the least became similar to drunk and those who least seemed attacked by madness or dead.
Why are there toxic honeys?
Multitudes of plants produce toxic nectar. Remember that bees make honey with floral nectar, which is the reward that plants give to their pollinators. What, then, is the biological rationale for producing toxic nectar? Why does a plant pump substances potentially harmful to its messengers into its flowers?
Although there are many studies on this phenomenon, the exact reasons are still unknown. Still, the researchers have some hypotheses.
1. Pollinator fidelity hypothesis. Many bees are more resistant to toxic alkaloids in nectar than some lepidoptera (butterflies). Perhaps some plants introduce toxic compounds into their nectar to deter inefficient pollinators. This would lead to greater specialization among toxin-immune pollinating insects.
2. The nectar thief hypothesis, emerged thanks to the study of the American catalpas, trees with a powerful arsenal of poisonous substances that are lethal to almost all herbivores. This idea is similar to the previous one, only it extends to all nectar- stealing organisms that escape with the sweet unpolonized loot. Thus, it would be a defensive response of the plant.
3. Microbial hypothesis. Sugary nectar can be a breeding ground for microbes, and plants may pump toxic compounds into their nectar to keep it aseptic.
4. Finally, it could be that the toxic nectar does not have any benefit for the plant. Perhaps it is the result of the genetic selection of defense compounds in other parts of the plant desired by herbivores, which would be expressed in nectar. It would be one more example of pleiotropy, the phenomenon whereby a single gene is responsible for distinct and unrelated phenotypic effects.
So where does science take us with these hypotheses? Does the data support any of them? This is where things get cloudy as if one had ingested crazy honey. The evidence that supports the different hypotheses is scarce. Simply put, it is still too early to tell whether toxic nectar is an adaptive evolution or not. It is necessary to go deeper into the subject. If you are ever looking for a doctoral thesis project, this is a great opportunity. In the meantime, do yourself a favor and avoid crazy honey.
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