Star Fruit is harmful for kidney patients, but it is safe for healthy persons.

Safety use of Star Fruit Juices.

Averrhoa carambola or Star fruit is a seasonal fruit, originally from Sri Lanka (formerly Ceylon) and the Moluccas Islands, Indonesian people recognize Star fruit as Belimbing, it has been cultivated in southeast Asia and Malaysia for many centuries. Averrhoa carambola belongs to the Oxalidaceae family, It is also found in southern China, Taiwan, India, Philippines, Australia, Central America, Africa and Brazil, in the tropical and subtropical areas. It is served either as freshly sliced fruits, as a naturally fresh beverages or as an industrialized juices, and sometime used in restaurants for decorative purposes throughout the world.

Star fruits are an excellent source of Vitamin C, naturally sodium and cholesterol free, it is low in fat, it contains high oxalic acid (see below), an average of 0.50 gram per 100 ml of juice. Star fruits contain a neurotoxin, which is not present in other fruits, affecting the brain and nerves, the various star fruit subspecies contain different neurotoxin that is suspected to accumulate in blood, cross the blood-brain barrier. In healthy persons, the kidneys filter it out, excreted it from the blood quickly and thus they do not suffer from its effect when a reasonable portion of the fruit is consumed, but in kidney patients, patients with renal failure condition, it cannot be removed and worsens their condition, So it is highly advisable:

• for kidney patients (renal failure patients) to avoid eating star fruit, while,
• for people with normal kidneys have no problem with the star fruit intoxication, but do beware of over consumption.

Cases on Star Fruit intoxications:

There have been reports of hiccup, confusion, and occasional fatal outcomes in uraemic patients after ingestion of star fruit. a Neurotoxin from star fruit has been implicated, although the exact nature of this toxic substance has not been identified. A group of seven patients is described from the dialysis centers at Queen Mary and Tung Wah Hospitals 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. The close temporal relationship of ingestion of star fruit and onset of symptoms strongly suggests the existence of a causal relationship between the two. It is recommended that uraemic patients (kidney patients / renal failure patients) should totally abstain from star fruit due to these rare but potentially fatal complications.

It is said that these symptoms are caused by the oxalic acid and a kind of neurotoxin contained in the star fruit. However, the claim of oxalic acid being problematic, in this case is controversial as the other foods that contain higher level of oxalic acid such as spinach (note: USDA: Spinach (Spinacia oleracea L) contains 5.3 % to 11.6 % oxalic acid on a dry weight basis, but there are significant differences in oxalate concentration among varieties.) do not seem to cause the symptoms, oxalate is found in a lot of food and generally healthy people would have no problem with it. The Brazilian researchers Carolino et al. (2003) have proven that the AcTx, a neurotoxic compound found in star fruit, is the causal to the convulsion after ingestion, for people with normal kidneys, this compound can be excreted from the blood quickly and thus they do not suffer from its effect when a reasonable portion of the fruit is consumed. Chemical characterization of AcTx showed that this compound is a nonproteic molecule with a molecular weight less than 500, differing from oxalic acid. This neurotoxic fraction of star fruit may be considered a new tool for neurochemical and neuroethological research.

A service of the US National Library of Medicine and the National Institute of Health (pubmed), in a published article: “Neurotoxic effects of Carambola in rats: the role of oxalate”, stating that Star fruit contains neurotoxins and oxalate. Oxalate can lead to kidney stones, but it would take a large amounts and many years to lead to such condition.Pubmed gives a conclusion: Oxalate is a main constituent of carambola neurotoxicity, this finding suggests that patients with carambola intoxication should be treated for oxalate toxicosis.

What is Neurotoxin ?

A neurotoxin is a substance which inhibits the functions of neurons. Neurons are found throughout the brain and nervous systems, and the function of these unique cells is critical for a variety of tasks, ranging from autonomic nervous system jobs like swallowing to higher-level brain functions. Neurotoxins can work in a variety of ways, with the danger of exposure varying, depending on the neurotoxin involved and the dosage.

In some cases, neurotoxins simply severely damage neurons so that the neurons cannot function well. Other neurotoxins attack the signaling capability of neurons, by blocking releases of various chemicals or interfering with the methods of reception for such transmissions, and sometimes telling neurons to send false signals, furthermore, a neurotoxin may also destroy neurons altogether. The body actually generates some neurotoxins, many of the neurotransmitters produced to send messages across the nervous systems can be dangerous in high amounts, sometimes the body produces neurotoxins as it responds to a threat to the immune system.

Neurotoxins are also present in large numbers in the natural environment; some venomous animals produce neurotoxins, while heavy metals such as lead are also neurotoxins, there are also many plants that produce Neurotoxins.

Samples of Plants containing Neurotoxin:

1. Conium maculatum (Poison hemlock): coniine a neurotoxic alkaloid.
2. Karwinskia humboldtiana (Buckthorn, coyotillo, tullidora): Paralysis (demyelination of peripheral nerves).
3. Atropa belladonna (Solanaceae family): atropine, scopolamine.
4. Strychnos family (curare): respiratory failure.

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