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Lychee fruits have evidently been widely used in many cultures for the folk medicine treatment of everything from farts to testicular swelling. Yeah, but arsenic, mercury, and lead are also included in many “traditional” remedies; so, how much is that really telling us? But lychees have been apparently shown to exhibit numerous health benefits. Yeah, but they cite studies like this. The protective effect of a lychee flower extract on cardiovascular health in a high-fat fed hamster. What are you supposed to do with that? You don’t even eat the flowers. Oh, and you’re not a hamster. Hard to argue with this, though: a flavor that is sweet, fragrant, and delicious, which is why I love them so much. But then, I saw papers like this: “A child-killing toxin emerges from shadows. Scientists link mystery deaths… to the consumption of lychees.”
In Vietnam, it was called “nightmare” encephalitis—unexplained outbreaks in children coinciding with lychee harvesting. Children go to bed fine, but they wake up the next morning seriously ill with brain function derangement and seizures, or they don’t wake up at all. The same thing in India, killing up to nearly two out of three kids affected in some places. And we’re talking thousands of kids, becoming one of the most pressing public health emergencies in the country. It was evidently one of the three long-standing mystery diseases on Wikipedia, remaining a mystery for more than two decades.
All clinical samples were negative for known brain viruses. So, some investigators thought it was caused by some unknown virus; others thought it might have been the pesticides used in the orchards. All we knew is that it seemed to coincide with the lychee harvest. So, maybe the fruit was attracting fruit bats, and then, the mosquitos were transferring some new virus from bats to people. Okay, but then why would toddlers be spared? Mosquitoes bite infants, too.
So, maybe kids were swapping spit with the fruit bats eating half-eaten fruits? Or, maybe it was just because it was summertime, and they were all just getting heat stroke? Okay, then why wasn’t the heat or pesticides affecting adults?
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.” Perfectly well when they went to bed, but by the next morning, sick, then unconscious, and then, both dead within 48 hours. This is all thanks to eating unripe ackee fruit, which contains a toxin known as hypoglycin, that prevents your liver from churning out blood sugar all night long to keep your brain alive while you sleep. And ackee is a member of the soapberry family, just like lychees. Aha!
But Muzaffarpur is a leading lychee producer, and experts at the National Lychee Center claimed they “completely refuted” the lychee link. But independent researchers found it. Lychee fruit contains methylene cyclopropyl-glycine, a.k.a. the exact same hypoglycin toxin.
So, in the setting of malnourished children who already start out with depleted energy stores in their livers (due to going to bed hungry and general malnutrition), low blood sugar sets in, and due to the excessive lychee consumption, the production of new energy is blocked, and the trouble starts. It’s a social tragedy that children are dying in the 21st century due to low blood sugar, which could be easily corrected. And 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, public health workers sought instead to treat the cause by educating folks that “no child should go to bed at night without eating a cooked meal, and for parents to restrict children eating lychees in the evening to none or very few”. And thankfully, by applying these recommendations, the disease incidence had been dramatically reduced. In hindsight, it appears China was already warning citizens about the dangers of lychees a decade earlier, but word had apparently just not gotten around.
What are the implications in the West? In the U.S., the FDA 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, [they figure] 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.” Small quantities? You don’t know how I eat lychees. I used to sneak into movie theaters with big bags of them—pounds of them—because they were just so much fun to peel and eat. How many is too many?
In a series of a few hundred poisoning cases, people reported eating 300 grams to a kilo. Each lychee is about 10 grams; so, that’s 30 to 100 fruit. Most of the cases were in children; so, we can probably safely say 30 to 100 lychees is too many at a time for kids. What about adults? In a self-experiment, a researcher just downed some lychees and measured the hypoglycin levels in his blood and urine. Based on how much was in the fruit, how much he ended up peeing out, and the urine levels found in victims, one can roughly calculate that adults shouldn’t eat more than 200 fresh lychees at a time, or about 10 cans worth.
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