Ackee Fruit Toxicity

Updated: Apr 23, 2015
  • Author: Dave A Holson, MD, MBBS, MPH; Chief Editor: Timothy E Corden, MD  more...
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Overview

Background

Ackee, the national fruit of Jamaica, is a food staple in many Jamaican diets. The fruit is rich in essential fatty acids, vitamin A, zinc, and protein. [1, 2] Consumption of unripe ackee fruit, however, can lead to potentially fatal toxicity, known as Jamaican vomiting sickness.

The word "ackee" originated from the Twi language. The ackee tree is a tropical evergreen tree that can grow as tall as 40 feet. Its leaves are broad and pinnate; its approximately 10-cm wide, 100-g fruit may be colored anywhere from straw to bright red. The fruit splits open while still on the tree to reveal three glassy black seeds surrounded by a thick, oily, yellow aril. (See the images below.)The fruit should be allowed to open and ripen naturally on the tree.

Freshly picked Ackee fruit Freshly picked Ackee fruit
Black seeds surrounded by a thick, oily, yellow ar Black seeds surrounded by a thick, oily, yellow aril (edible portion).

The ackee tree is indigenous to West Africa, where it is called ankye or ishin. Thomas Clarke, Jamaica's first botanist, introduced the plant to the island in 1778. However, the ackee tree, Blighia sapida, was named after the infamous Captain William Bligh who took the breadfruit tree to the West Indies. The tree also grows in other West Indian Islands such as Cuba, Haiti and Barbados, in Central America, and in Southern Florida. [3]

An association between ackee poisoning and Jamaican vomiting sickness was first noted in 1875 and documented in 1904. In 1937, Jordan and Burrows found a water-soluble toxic material in the seed and pods of the ackee fruit. In 1954, Hassal et al were the first to isolate two toxic compounds in their crystalline form. These compounds were called hypoglycin A and hypoglycin B because of their hypoglycemic activity.

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Pathophysiology

Two toxic water-soluble substances can be extracted from the fruit. The first toxin, hypoglycin A, is L-α -amino-β -[methylene cyclopropyl]propionic acid. Hypoglycin B is a γ -L-glutamyl derivative of hypoglycin A and is less toxic than hypoglycin A. Hypoglycin A, but not hypoglycin B, can be found in the aril of the fruit. The unripe fruit has a much higher concentration of hypoglycin A (approximately 20 times) than that of the ripe aril. Both components are found in the seeds. Therefore, the seeds and the membrane at the base of the seed mantle are always poisonous.

Hypoglycin A, which is now simply called hypoglycin, is metabolized by means of transamination and oxidative decarboxylation to methylene cyclopropyl acetic acid (MCPA). MCPA forms nonmetabolizable carnitine and coenzyme A (CoA) esters, thereby depressing tissue levels of these cofactors and making them less available for other biochemical reactions. Hypoglycemia results because both CoA and carnitine are necessary cofactors for long-chain fatty acid oxidation and because oxidation is a requisite for active gluconeogenesis. MCPA also inhibits the dehydrogenation of several acyl-CoA dehydrogenases, including butyryl CoA, glutaryl CoA, and isovaleryl CoA. As a result of the inhibition of butyryl CoA dehydrogenase, the oxidation of long-chain fatty acids stops at the level of hexanoyl CoA and butyryl CoA. This effect leads to the decreased production of nicotinamide adenine dinucleotide (NADH) and acetyl CoA.

Because NADH and acetyl CoA are required as a cofactor of 3-phosphoglyceraldehyde phosphate dehydrogenase and as an activator of pyruvate carboxylase, respectively, their diminished concentration contributes to the inhibition of gluconeogenesis. The inhibition of glutaryl CoA dehydrogenase results in the accumulation of glutaryl CoA, which could inhibit transmitochondrial malate transport, a rate-limiting step in the early phase of gluconeogenesis, and consequently suppress gluconeogenesis. Altered levels of circulating insulin do not cause hypoglycemia associated with hypoglycin action.

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Epidemiology

Frequency

United States

Ackee is illegal in the United States; therefore, underreporting may occur. To date, 2 cases of ackee poisoning have been reported in the United States. The first was in Ohio in a Jamaican woman who presented with Jamaican vomiting sickness after a meal of ackee fruit. The second was in Connecticut in a young Jamaican man who presented with cholestatic jaundice secondary to the chronic ingestion of ackee fruit.

International

The epidemiology of ackee poisoning has not been well characterized, and the true incidence and mortality rate are believed to be underreported. At the request of the Jamaican Ministry of Health (JMH), the Centers for Disease Control and Prevention (CDC) identified 38 cases of Jamaican vomiting sickness and 6 deaths from 1989-1991. This problem is endemic in Jamaica; 271 cases have been reported to the JMH since 1980.

In 1998, an unexplained outbreak of epidemic fatal encephalopathy (EFE) occurred in Burkina Faso in West Africa. The only factor associated with EFE was the presence of ackee trees within 100 m of the households. The consumption of unripe ackee fruit possibly caused this epidemic.

In late 2000, the CDC provided technical support to the Ministry of Health in Haiti during an outbreak of ackee poisoning in the northern region of that country. [4, 5] More than 100 cases of acute illness and death were reported.

From 1998-2001, reports detailed 16 deaths of children in Surinam along the River Maroni, which separates Surinam and French Guyana. The deaths were subsequently linked to ackee fruit poisoning as result of the misuse of the plant by Maroon witch doctors to "cure" some pathologies especially acute forms of diarrhea in children. [6]

Mortality/Morbidity

Before treatments were developed, the mortality rate was as high as 80%. No deaths from ackee fruit poisoning have been reported in the United States. In Jamaica, 6 deaths were reported in 1989-1991. A link between ackee fruit poisoning and unexplained deaths of preschool children in West Africa has been postulated.

Race

Ackee is consumed mostly in West Africa and Jamaica; therefore, most cases have occurred in blacks.

Sex

No difference in the sex distribution is noted.

Age

In Jamaica, the annual rate of ackee poisoning is 2 cases per 100,000 persons younger than 15 years and 0.4 case per 100,000 persons older than 15 years.

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