Related species: Bilimbi (Averrhoa bilimbi L.)

 

Food
A food, which may result in allergy symptoms in sensitised individuals.

The fruit comes from a tree growing up to 12 metres. This tree has been cultivated in Southeast Asia and Malaysia for hundreds of years, and now is also found in many places in the New World with appropriate climates. The fruit, ovate to ellipsoid and 6 to 13cm in length, has a yellowish or greenish, waxy, translucent skin. Slices cut in cross-section are star-shaped, with five corners. The flesh is yellow, translucent, crisp and very juicy. There may be up to 12 flat, thin, brown seeds. There are 2 distinct classes of Carambola: the smaller, very sour type, richly flavored, with more oxalic acid; and the larger, "sweet" type, mild-flavored, with less oxalic acid.

 

Environment
Ripe Carambolas are eaten out of hand, sliced and served in salads, or used as garnish. Their juice is very popular in the East. They are also cooked in puddings, tarts, stews and curries. The sweeter type may be cooked green as a vegetable. They can serve as the main ingredient of sherbet, seasoning, jelly, or relish. The fruits may be stewed, dried, canned, pickled or candied.

 

Medicinally, the fruit is used against haemorrhages, fevers, diarrhoea, eye afflictions, eczema, and kidney, liver and bladder complaints. There are, however, health risks from the oxalic acid in fully ripe Carambolas: see under Other reactions.

 

The acidic types of Carambola are used to clean and polish metal, especially brass, as they dissolve tarnish and rust. The juice is also used as a stain remover. Unripe fruits serve as a mordant in dyeing.

 

Allergens
No allergens from this food have yet been characterised.

Potential Cross-Reactivity

No cross-reactivity has been reported to date.

Carambola may rarely induce symptoms of food allergy in sensitised individuals.

 

Other reactions
Six patients in a dialysis programme were apparently intoxicated by ingestion of 2-3 fruits or 150-200 ml of the juice and developed a variety of symptoms ranging from insomnia and hiccups to agitation, mental confusion and (in one case) death. The effects were believed to come from an excitatory neurotoxin in the fruit (1). A recent study concluded that oxalate is a main contributor to Carambola neurotoxicity, rather than an excitatory neurotoxin. Carambola contains a large quantity of oxalate, which can induce depression of cerebral function and cause seizures (2).

 

There have been other reports of hiccup, confusion, and occasional fatal outcomes in uraemic patients after ingestion of Star fruit. A group of 7 patients is described who developed symptoms including hiccup, confusion, vomiting, impaired consciousness, muscle twitching and hyperkalaemia shortly after ingestion of Star fruit. Symptoms of most patients resolved after intensified dialysis or spontaneously, and no mortality was observed (3).

 

Further support for oxalate as the cause of the adverse effects seen is reported in 2 other cases, where patients developed nausea, vomiting, abdominal pain, and backache within hours of ingesting large quantities of sour Carambola juice; then acute renal failure followed. Both patients needed hemodialysis for oliguric acute renal failure, and pathologic examinations showed typical changes of acute oxalate nephropathy. Renal function recovered 4 weeks later without specific treatment. Sour Carambola juice is a popular beverage in Taiwan, but commercial juice usually is prepared by pickling and dilution processes that reduce oxalate content markedly, whereas pure fresh or semi-fresh juice for traditional remedies, as had been used in the above cases, contains high quantities of oxalate. An empty stomach and a dehydrated state may pose additional risks for development of renal injury (4).

 

Compiled by Dr Harris Steinman, harris@zingsolutions.com