Star Fruit-Induced Chronic Kidney Disease

Star fruit (Averrhoa carambola) is also known as carambola. It is the fruit of a species of tree that is native to tropical Southeast Asia. Nowadays, the tree is cultivated throughout tropical areas of the world.

The yellow fruit has distinctive ridges running down its sides. When cut in cross-section, the parts resembles a star, giving it the name of star fruit. The entire fruit is edible. It is usually consumened raw. It can also be cooked or made into relishes, preserves, garnish, and juices.

But star fruit has a bit of a dark side because it contains minute amounts of caramboxin (CBX), a potent neuroxin[1]. Individuals who already have some types of kidney disease are susceptible to adverse mild to severe neurological effects including intoxication, hiccups, vomiting, asthenia (abnormal physical weakness or lack of energy), mental confusion, seizures, coma, and death after eating star fruit.

Caramboxin has been identified as the neurotoxin responsible for these effects. It is a non-proteinogenic amino acid that stimulates the glutamate receptors in neurons. Its chemical structure is similar to the amino acid phenylalanine. Caramboxin is an agonist of both NMDA and AMPA glutamatergic ionotropic receptors with potent excitatory, convulsant, and neurodegenerative properties[1].

A possible interaction between caramboxin and oxalic acid, both present in starfruit can lead to both neurotoxic and nephrotoxic effects.

Consuming large amounts of starfruit or its juice on an empty stomach is not recommended, even for individuals with normal kidney function[2].

We propose to call this Chronic Kidney Disease of non-Traditional causes (CKDnT): Star Fruit-Induced Chronic Kidney Disease.

[1] Garcia-Cairasco et al: Elucidating the neurotoxicity of the star fruit in Angewandte Chemie - 2009
[2] Moyses Neto et al: Star fruit: simultaneous neurotoxic and nephrotoxic effects in people with previously normal renal function in NDT Plus – 2009. See here.