Lychees and Ackee Fruits: Toxins and Their Effects

Lychees are tropical fruits with a pleasant fragrance and a sweet flavour. Ackees are the national fruit of Jamaica and have a slightly savoury taste. Both fruits are very popular in some parts of the world. In addition, both can be dangerous when they are unripe.

The lychee and ackee plants belong to the soapberry family, or the Sapindaceae, and contain similar toxins. In specific circumstances, unripe lychees can cause hypoglycemia (low blood sugar) and a dangerous brain dysfunction that may be deadly. Ackee fruits that are not ripe can cause severe vomiting and other unpleasant symptoms. The illness is sometimes fatal, especially if it’s not treated.

Lychees and ackee fruits are both available in North America, at least in some places and at some times of the year, either in fresh or canned form. They can be an enjoyable addition to the diet. Care is needed when choosing and preparing them, however, especially in the case of ackee fruits.

The lychee or litchi plant is an evergreen flowering tree that is native to China. Its scientific name is Litchi chinensis. The small fruits are round, ovoid, or heart-shaped and are borne in clusters. The fruits have a maximum length of around two inches. Most are smaller than this, however. The outer rind of the fruit is usually red, orange-red, or pink and has a bumpy appearance. There are yellow patches on some lychees. One variety has yellow-green fruits.

The inner flesh of a lychee is white, smooth, and translucent. A brown seed is located in the middle of the flesh. Some fruits have unusually small seeds, which is considered to be a desirable feature by both growers and eaters. The flesh is technically called the aril and is the only part of the fruit that is edible. An aril is a covering that partially or completely surrounds a seed. It’s sometimes produced by the seed itself and is frequently fleshy.

Raw lychees are an excellent source of vitamin C and a good source of copper. They also contain a useful amount of vitamin B6 and potassium. Their taste and nutrients make them a great fruit to eat. It’s important that they’re ripe, however, at least until we have a better understanding of the fruit’s potential toxicity. Unripe lychees are completely green in colour.

Ever since the 1990s, investigators have been seeking an explanation for the puzzling deaths of Indian children after eating lychees. Various theories have appeared. These include poisoning by pesticides, a viral infection due to animal droppings on the fruit, and heavy metal poisoning.

A major analysis that linked the problem to lychee toxins was published in early 2017. The analysis was based on poisonings that occurred in 2014 in an area containing many orchards with lychee trees. The poisonings took place from May to July, which is the lychee season, and were absent during the rest of the year. The affected children visited the orchards and ate lots of lychees.

After eating unripe fruit, the children went to bed without exhibiting any symptoms. During the night, however, some of them woke up crying. This was followed by seizures, coma, and often death, even when the children were taken to a hospital. The children had low blood sugar and encephalopathy, or brain dysfunction.

The researchers discovered that many of the affected children—especially those that died—didn’t eat evening meals or ate only small ones. The investigators say that most of the children came from poor socioeconomic backgrounds. It’s possible that hunger was the reason for the willingness of some children to eat unripe lychees. The researchers found that many of the children ate so many lychees that they didn’t want an evening meal even when it was available, however. The combination of eating a large number of lychees without eating an adequate amount of other food produced the most serious symptoms.

Unripe lychees contain two toxins—methylenecyclopropyl glycine or MCPG and hypoglycin A. These are related chemicals with similar but not identical structures. The investigators found metabolites of the toxins in many of the children that ate the unripe fruit. A metabolite is a substance produced in the body from the chemical in question.

Humans eating a satisfactory diet are normally able to regulate their blood sugar level (or blood glucose level) within a narrow range. The sugar is used by cells as an energy source. Excess glucose from the diet is stored in the liver as glycogen. If someone hasn’t eaten for a while, glycogen is broken down to produce glucose. A constant blood sugar level is necessary for normal brain function.

According to the researchers, young children have a limited ability to store glycogen in their liver. As a result, when they haven’t eaten for a while they need to convert fatty acids to glucose. The lychee toxins interfere with this process. Therefore after eating a sufficient number of unripe lychees children may experience hypoglycemia. In some cases the blood sugar level becomes very low during the night. This harms the brain and is responsible for the dangerous and distressing symptoms of lychee poisoning.

The investigators say that the solution to the lychee problem is for parents to warn their children about eating the fruit and to ensure that the children get a good evening meal. The food should help to prevent the blood sugar from dropping during the night. Hopefully parents can afford to provide the meal. The number of deaths has decreased significantly since the recommendation was made, but children are still dying. The scientists also recommended that children taken to a hospital after being poisoned receive “rapid glucose correction”.

Like the lychee plant, the ackee plant (Blighia sapida) is an evergreen tree that produces flowers and fruits. It’s native to West Africa. The fruit is large and is red, orange, or yellow in colour. The edible part of the fruit is the cream or pale yellow flesh or aril round the seeds. The aril is often referred to as simply “ackee”.

Ackee and saltfish is the national dish of Jamaica and is a popular meal. The cooked ackee is a rich yellow colour and looks a lot like scrambled eggs. Its taste is reportedly quite mild, but some people love it. Some say that it has a nutty flavour while others say that it tastes a bit like cheese. It’s very important to eat only ripe ackee fruits and to eat only the properly prepared aril.

Ackee poisoning is also known as Jamaican vomiting illness. It appears in both adults and children. Children are more likely to die from the illness. It’s important that people of all ages get medical treatment for the condition. The toxin in the fruit is hypoglycin A.

Some of the symptoms of the illness are the same as ones found in lychee poisoning. There are differences between the two conditions, however. As the alternate name for the illness suggests, severe vomiting is a dominant symptom of ackee poisoning. Vomiting occurred in some of the children investigated in the lychee poisoning analysis, but not in most of them.

Some common symptoms of ackee poisoning are listed below. Hypoglycemia is also a characteristic of the disorder. It’s thought that poor nutrition may make symptoms worse.

  • Stomach discomfort begins several hours after eating the unripe fruit.
  • Vomiting begins suddenly.
  • The person may experience sweating, rapid breathing, rapid heartbeat, headache, numbness, tingling, and weakness.
  • A disturbed mental state may develop.
  • A second bout of vomiting sometimes occurs.
  • Seizures and coma may follow this vomiting.

I’ve eaten lychees, which are available in stores and restaurants during the summer where I live. I haven’t eaten ackee, however, and have never seen it in the stores. If it was available I wouldn’t eat it unless I could prepare it myself or unless I was confident that it was prepared by someone who knew how to deal with the fruit.

Unripe fruit contains a high level of hypoglycin A and is very poisonous. Ripe fruit still contains hypoglycin A, but the level is much lower. Hypoglycin is a water soluble chemical. If the ackee is washed and then cooked in water, the amount of toxin should fall to a safe level. Experts in dealing with the fruit give the following advice for making ackee safe to eat.

  • The fruit should never be forced open to get to the edible part. Instead, someone wishing to eat ackee should wait until a fruit is fully ripe and opens on its own before picking it.
  • The aril should be removed and the seeds and rind safely disposed of so that children and pets can’t reach them.
  • If a pink membrane sticks to the aril, this should peeled away.
  • The aril should then be rinsed with water and the water discarded.
  • The washed aril should be boiled in water until tender.
  • The cooking water must be discarded.
  • Many people like to stir-fry the ackee with other food at this point.

Canned lychees are available throughout the year where I live. Canned ackee is available in some places. This may sound like a safer product than the fresh fruit and would certainly be easier to use. The canned product is periodically banned in the United States when the FDA (Food and Drug Administration) finds too much hypoglycin A in a particular brand, however. If I was thinking of buying canned ackee I would do some research about the product and its manufacturer first.

Exploring foods from other parts of the world is often an enjoyable activity. It’s important to learn how experts prepare a food that is new to us, however. Their knowledge has enabled them to stay safe while eating the food and can do the same for us.

Unripe lychees seem to be dangerous only under certain conditions; unripe ackees seem to be dangerous for many of us. Both fruits can be interesting additions to the diet but need to be treated with respect.

Information about Litchi chinensis from the Missouri Botanical Garden

Nutrients in raw lychees from SELFNutritionData

“Association of Acute Toxic Encephalopathy With Litchi Consumption” in 2014 from The Lancet

Acute encephalitis syndrome in Indian children after eating lychees in mid 2019 from The Guardian

Blighia sapida facts from the Missouri Botanical Garden

Ackee fruit toxicity from Medscape