Snopes.com, the estimable rumor-investigating site, recently reprinted a piece titled "Star Fruit Can Kill" that has circulated on the Internet since at least May of 2008. The piece asserts that a kidney patient in Malaysia went into a coma and died after eating carambola, popularly known as star fruit due to the star-shaped cross sections it forms when sliced. It also states that other kidney patients have died of the same cause, and "the risk of death is high if you are having kidney ailments!"
As it turns out, while some details of the piece cited were indeed hyperbole there is some evidence that kidney patients can be "intoxicated" and even die as the result of ingesting carambola. A report titled "Intoxication by star fruit (Averrhoa carambola) in 32 uraemic patients: treatment and outcome" in the journal Nephrology Dialysis Transplantation, published in 2003, cited several deaths of kidney patients (meaning people who are on supportive or dialysis treatment) associated with star fruit ingestion. The culprit is believed to be a neurotoxin and a high level of oxalic acid, though this is far from certain, and some nutritionists believe the danger of carambola, even to kidney patients, has been overblown.