Food Attack ! Starfruits

Star fruit is the fruit of Averrhoa carambola, a perennial tree in the family Oxalidaceae. It was originated from South Asia, distributed all over S.E.Asia, the South Pacific, parts of East Asia, and tropical America.

The fruit starts out green, and goes to yellow as it ripens, though it can be eaten at both stags. The flesh is crunchy, slightly tart, acidic, sweet taste, reminiscent of pineapples, apples and sometimes kiwi fruit.

Health Benefits

Star fruit is rich in antioxidants and vitamin C and low in sugar, sodium and acid.

Regular consumption of the fruit is believes to help regulate blood pressure, reduce cholesterol levels and lower risk of cardiovascular problems.

Health Risks

However, people with kidney problem are not advised to consume the fruit. Star fruit contains oxalic acid which can combine with minerals to form tiny crystals known as oxalates. A problematic kidney may not be able to efficiently excrete the oxalate, of which may get lodged in the stomach, kidneys and bladder as ‘stones’. ( 80% of kidney stones derive from calcium oxalate ).

Bonding of calcium, iron, sodium, magnesium or potassium will deprive the body of the essential minerals. However, the some researches confirm that nutrient deprivation by oxalic acid is relatively small.

Clinical symptoms and outcomes of uraemic patients ingesting star fruit are quite variable and may progress to death. The most common symptoms are persistent and intractable hiccups, vomiting, variable degrees of disturbed consciousness, decreased muscle power, limb numbness, paresis, insomnia, parenthesis, and even seizures. Patients with severe intoxication who were not treated with peritoneal dialysis may not survive.(1)

To avoid acute oxalate nephropathy, pure sour star fruit juice should not be consumed in large amount, especially on an empty stomach or in a dehydrated state.(2)

Source :

1. Miguel et al, Intoxication by Star fruit in 32 Uraemic Patients, Nephrol Dial Transplant (2003) 18:120-125

2. Chen CL, Fang HC, Chou KJ, Wang JS, Chung HM. Acute Oxalate Nephropathy after Ingestion of Star Fruit. Am J Kidney Dis. 2001 Feb;37(2):418-22.

What is Oxalic Acid ?

Oxalic acid is an organic compound with molecular formula C₂H₂O₄. It s relatively strong acid, about 3,000 times stronger than vinegar. Oxalic acid is colorless, organic compound that occurs naturally in plants, animals and in humans. It is an important element, even essential, to maintain and to stimulate peristaltic motion.

How Many is Star Fruit Enough ?

A low oxalate diet should provide less than 50mg oxalate per day. In general, oxalic acid is found in higher concentrations in dark-green leafy vegetables such as spinach and beetroot. Tea, chocolate and other cocoa products have more oxalic acid even compare to star fruit.

It is certainly one shouldn’t avoid eating vegetable just because the present of small amount of oxalic acid. The amount of oxalic acid is too small to do harm to our body.

How Many Star Fruit is Fatal ?

In humans, oxalic acid has an oral LD_Lo of 0.6g/kg. LD_Lo is the lowest dosage per unit bodyweight of a substance known to have resulted in fatality in a particular animal species.

Star fruit contains some 958mg/100g of oxalic acid. Meaning that limit per day for an average man of 60kg body weight is 4 medium size star fruit.

Puerto Rican technologist found the oxalic acid content of ripe star fruit to average 5g/1liter of juice. Again, a simple calculation shows that an average man of 60kg body weight needs to drink 7.2liter of pure star fruit juice to get himself killed. 7.2liter of pure star fruit is certainly an exorbitant amount !