There is a toxin in lychee fruit that can be harmful, but is it harmful only under certain circumstances?
Lychee fruits have been widely used in many cultures for the folk medicine treatment of everything from farting to testicular swelling. (Arsenic, mercury, and lead are also included in many “traditional” remedies.) Lychees have also apparently “been shown to exhibit numerous health benefits,” but the studies cited include ones like this: “Protective Effect of a Litchi [Lychee]…-Flower-Water-Extract on Cardiovascular Health in a High-Fat/Cholesterol-Dietary Hamsters.” What are we supposed to get from that? We don’t eat lychee flowers…and we aren’t hamsters. Hard to argue with this, though: “Flavor is sweet, fragrant, and delicious,” which is why I love them so much. I then saw this: “A child-killing toxin emerges from shadows. Scientists link mystery deaths…to the consumption of lychees.”
In Vietnam, it’s called “nightmare” encephalitis. There were unexplained outbreaks in children coinciding with lychee harvesting. Children go to bed feeling fine, but they wake up the next morning “seriously ill with brain function derangement and seizures”—if they wake up at all. The same in India, killing up to nearly two out of three kids affected in some places. We’re talking about thousands of kids, so it became “one of the most pressing public health emergencies in India.” It was one of the “three long-standing mystery diseases listed in Wikipedia” and remained a mystery for more than two decades.
All clinical samples were negative for known brain viruses. So, some investigators thought it was caused by an unknown virus, while others thought it might have been due to the pesticides used in the orchards. All we knew was that it seemed to coincide with the lychee harvest. So, might the fruits have attracted fruit bats, then mosquitos could have fed on the infected bats and transferred some new virus from bats to people? Maybe, but why would toddlers and babies be mostly spared? Mosquitoes bite infants, too.
So, were kids swapping spit with the fruit bats by eating half-eaten fruits? “The investigators noted colonies of fruit-eating bats and the tendency of children eating fruits to fall to the ground and suggested the possibility of a bat virus (through saliva contamination on fruits) as a cause of the disease.” Or maybe it was because it was summertime, and they were all just getting heat stroke? Maybe, but why weren’t the pesticides or the heat affecting adults, too?
One of the clues that finally helped investigators tease out the mystery was that the children consistently had low blood sugars—in some cases, fatally low blood sugars. That kind of sounds like “Jamaican vomiting sickness.” Two children “were perfectly well” when they went to bed, but, by “the next morning, they started to vomit and were weak,” then unconscious, then both dead within 48 hours. That was all due to eating unripe ackee fruit, which contains a toxin known as hypoglycin, which prevents our liver from churning out blood sugar all night long to keep our brains alive while we sleep. Ackee is a member of the soapberry family, just like the lychee is. Aha!
As I discuss in my video Lychee Fruit and Hypoglycin: How Many Are Too Many?, Muzaffarpur is a leading lychee producer, and experts at the National Center for Litchi claim they “completely refuted” the lychee link. Nevertheless, independent researchers found it: Lychee fruit contains methylene cyclopropyl-glycine, nearly the same hypoglycin toxin “present in ackee fruits, popular in Jamaica.”
So, in the setting of malnourished children who already have depleted energy stores in their livers “(due to missed meals and poverty-related starvation),” low blood sugar sets in, and, due to the excessive consumption of lychee fruits, the production of new energy is blocked, and the trouble starts. “It is a social tragedy that children have to die in the 21st century due to…hypoglycemia [low blood sugar], which is an easily treatable condition and involves minimal costs.” It’s just as tragic that hungry children are forced to binge on lychees falling on the ground to get a meal. It’s like something out of Grapes of Wrath.
The happy ending, though, is that rather than just focusing on better treatments, local public health workers instead sought to treat the cause by educating people “that no child should go to bed at night without eating a cooked meal and for parents to restrict children eating litchis in the evening to none or very few.” Thankfully, “by applying these recommendations, the disease incidence had been dramatically reduced and death almost completely prevented.” In hindsight, it appears China had already started warning citizens about the dangers of lychees a decade earlier, but word had apparently not gotten around.
What are the implications in the West? In the United States, the Food and Drug Administration tried to protect people against poisoning with this toxin (which is not destroyed by heating) by mandating that canned ackee fruits coming into the country test below a certain level, but there are no such regulations when it comes to importing lychees. “Fortunately, the high cost of these imported fruits and the likelihood that [they] would be eaten in small quantities by well-nourished consumers, suggests there is little reason for concern in the USA.” That’s quite an assumption. Small quantities? You don’t know how I eat lychees. I used to sneak big bags of them—pounds of them—into movie theaters to snack on during the film. How many are too many to eat?
In a series of a few hundred poisoning cases, people reported eating 300 grams to a kilogram of lychee fruits. Each lychee is about 10 grams, so that’s 30 to 100 fruits. Most of the cases were children, though, so we can probably safely say 30 to 100 lychees are too many at one time for kids. What about adults? In a self-experiment, a researcher ate some lychees and measured the hypoglycin levels in his blood and urine, which stayed below the levels seen in the affected children. He ate 5 grams of canned lychee for each kilogram of his body weight, equivalent to about 45 lychee for the average American male, and didn’t suffer any ill symptoms.
What a fascinating story! A lot of research went into just this one topic, but it was all news to me, so I wanted to share it with you.
In general, Is Canned Fruit as Healthy? And, given the sugar content, How Much Fruit Is Too Much? Check out the videos to find out.
