NutriDex

The Supplement Research Compendium
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Starfruit (Carambola)

Averrhoa carambola

Crisp tropical star, safe only with healthy kidneys

Preliminary evidence 🍎Fruits

✚ Updated · How we grade evidence

Evidence tier
Preliminary
Research weight
Citations
10 verified / 10
Classification
Fruits
❝
What the evidence says. Early or small human trials; promising but not yet conclusive.

Nutrition per serving 1 medium (91 g)

91gSERVING
  • Water 83.2 g92%
  • Sugars 3.6 g4%
  • Fibre 2.5 g3%
  • Protein 1 g1%
  • Fat 0.3 g0%
What's in one serving, by weight — average composition (USDA).
Vitamin C35%Fiber9%Copper14%Potassium3%Folate3%Pantothenic acid7%
One serving as % of the adult daily requirement (FDA Daily Values). The bold outer ring = 100% of a day's needs.
28 kcal0.95 g protein2.5 g fiber0.3 g fat
NutrientPer serving% daily value
Vitamin C31 mg35%
Fiber2.5 g9%
Copper0.13 mg14%
Potassium121 mg3%
Folate11 mcg3%
Pantothenic acid0.36 mg7%
Magnesium9 mg2%
Sugars3.6 g0%

Composition data: USDA FoodData Central ↗

What is Starfruit (Carambola)?

Starfruit (Carambola) (Averrhoa carambola) is a fruit used for low-calorie, high-water fruit useful for weight-conscious and hydration-focused diets. NutriDex grades the human evidence as Preliminary. Starfruit is a low-calorie, water-dense tropical fruit that delivers a useful dose of vitamin C (about a third of the Daily Value per fruit) and insoluble fiber, plus a broad mix of flavonoids and phenolic acids with antioxidant activity in laboratory assays. The most robust human evidence about starfruit, however, concerns harm rather than benefit: dozens of case reports and case series document severe nephrotoxicity and neurotoxicity—intractable hiccups, vomiting, confusion, seizures, status epilepticus, and death—after ingestion by people with chronic kidney disease, and occasionally those with normal or only mildly impaired renal function. A 2013 chemistry study isolated caramboxin, a phenylalanine-like toxin that activates glutamatergic (AMPA/kainate) receptors and inhibits the GABAergic system, explaining the neurological effects, while high soluble oxalate drives oxalate nephropathy. The widely cited metabolic and anti-diabetic \"benefits\" come almost exclusively from in-vitro and rodent experiments; there are essentially no controlled human trials confirming any therapeutic effect. Overall the weight of human evidence is preliminary for benefits and clearer for risk. For most people with healthy kidneys, normal culinary amounts are considered safe and nutritious. Anyone with reduced kidney function or on dialysis should avoid it completely.

Purported Benefits

✓Low-calorie, high-water fruit useful for weight-conscious and hydration-focused diets
✓Meaningful vitamin C contribution (about a third of the Daily Value per fruit) supporting antioxidant defense and collagen synthesis
✓Dietary fiber (largely insoluble) that may aid satiety and bowel regularity
✓Rich source of polyphenols and flavonoids with antioxidant activity in lab models
✓Preclinically studied anti-hyperglycemic and anti-hyperlipidemic actions (animal/in-vitro only)
✓Traditionally used as a cooling, thirst-quenching food in tropical cuisines

Dosing & Compounds

Typical Dose
1 medium fruit (~91 g) or ~100 g sliced; avoid entirely in chronic kidney disease
Active Compounds
Vitamin C (L-ascorbic acid)Soluble oxalate / oxalic acid (anti-nutrient and nephrotoxin)Caramboxin (phenylalanine-like excitatory neurotoxin)Flavonoid glycosides (apigenin C-glycosides, quercetin, rutin)Proanthocyanidins / condensed tanninsBenzoquinone derivatives (e.g. 2-dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione)Insoluble dietary fiber (cellulose, lignin)Gallic acid and other phenolic acidsPotassium and copper

Safety & Cautions

CONTRAINDICATED in chronic kidney disease, end-stage renal disease, and dialysis patients—even a single fruit or glass of juice can trigger hiccups, vomiting, confusion, seizures, status epilepticus, and death (caramboxin neurotoxin plus oxalate nephropathy). Toxicity has also been reported with normal-to-moderate renal function, especially when consumed on an empty stomach, dehydrated, or in large quantity/concentrated juice. High oxalate content poses a kidney-stone risk in susceptible individuals and can cause acute oxalate nephropathy. Like grapefruit, starfruit inhibits CYP3A4 and can raise blood levels of interacting drugs (e.g. statins, certain calcium-channel blockers). If neurological symptoms appear after ingestion in a renal patient, urgent hemodialysis/hemofiltration is the recommended treatment. Educational only — always check with your doctor or pharmacist before combining Starfruit (Carambola) with any medicine.

Key Studies ★ 10 studies

Narrative review Yasawardene 2021 ✓ Full text
Narrative review of human reports (28 case reports plus 10 case series; 136 individuals): 69.1% had prior renal impairment; renal histology showed acute oxalate nephropathy, and neurotoxicity ranged from hiccups to status epilepticus, improving with hemodialysis.
Mechanistic review Yasawardene 2020 ✓ Full text
Mechanistic mini-review: nephrotoxicity attributed to oxalate deposition causing acute tubular necrosis and interstitial nephritis, while caramboxin drives CNS excitation via glutamate-receptor activation and GABA inhibition.
Phytochemistry/pharmacology review Luan 2021 ✓ Full text
Comprehensive review cataloguing ~132 isolated compounds (flavonoids, benzoquinones, glycosides) and antioxidant, anti-hyperglycemic, anti-hyperlipidemic and neuroprotective activities, while noting evidence is almost entirely in-vitro/animal with a gap in clinical and safety data.
Review de Oliveira 2015 ✓ Full text
Review concluding that star fruit neurotoxicity in chronic kidney disease is driven by caramboxin inhibiting the GABAergic system, producing effects from hiccups and confusion to seizures and death, and arguing for multidisciplinary patient warnings.
Case report Caetano 2017 ✓ Full text
Hemodialysis patient developed intractable hiccups, myoclonus and tonic-clonic seizures after bilimbi (Averrhoa bilimbi), a related Oxalidaceae fruit, supporting a shared caramboxin/oxalate neurotoxic mechanism with star fruit.
Case report Auxiliadora-Martins 2010 ✓ Full text
Fatal case of severe encephalopathy with nausea, vomiting, intractable hiccups, confusion and seizures after star fruit juice in chronic renal failure; patient died despite hemodialysis, highlighting under-recognition by intensivists.
Case report Chen 2010 ✓ PubMed
67-year-old with only moderate renal insufficiency developed hiccups, coma and seizures with a reversible occipital lesion (PRES) two hours after eating one fresh star fruit, reversing after emergency hemodialysis.
Case series Moyses Neto 2003 ✓ Full text
Series of 32 uremic patients intoxicated by star fruit: intractable hiccups in 93.75%, vomiting 68.7%, disturbed consciousness 65.6%, seizures 21.8%; prompt daily hemodialysis led to recovery while peritoneal dialysis/supportive care alone was often fatal.
Case report Signate 2008 ✓ PubMed
Two patients with previously unknown chronic renal insufficiency developed intractable hiccups, status epilepticus and cortical/thalamic MRI lesions after star fruit; both improved with continuous hemofiltration.
Chemical isolation / mechanistic study Garcia-Cairasco 2013 ✓ Full text
Isolated and characterized caramboxin, a phenylalanine-like neurotoxin from star fruit that activates glutamatergic AMPA/kainate receptors and inhibits the GABAergic system, explaining the seizures seen in intoxication.
10 sources cited · 10 verified Search all studies on PubMed ↗

Common questions about Starfruit (Carambola)

What is Starfruit (Carambola) used for?

Starfruit (Carambola) is most often taken for Low-calorie, high-water fruit useful for weight-conscious and hydration-focused diets, Meaningful vitamin C contribution (about a third of the Daily Value per fruit) supporting antioxidant defense and collagen synthesis, Dietary fiber (largely insoluble) that may aid satiety and bowel regularity, Rich source of polyphenols and flavonoids with antioxidant activity in lab models. Crisp tropical star, safe only with healthy kidneys

Does Starfruit (Carambola) work — what does the evidence say?

Preliminary evidence. Early or small human trials; promising but not yet conclusive. Starfruit is a low-calorie, water-dense tropical fruit that delivers a useful dose of vitamin C (about a third of the Daily Value per fruit) and insoluble fiber, plus a broad mix of flavonoids and phenolic acids with antioxidant activity in laboratory assays. The most robust human evidence about starfruit, however, concerns harm rather than benefit: dozens of case reports and case series document severe nephrotoxicity and neurotoxicity—intractable hiccups, vomiting, confusion, seizures, status epilepticus, and death—after ingestion by people with chronic kidney disease, and occasionally those with normal or only mildly impaired renal function. A 2013 chemistry study isolated caramboxin, a phenylalanine-like toxin that activates glutamatergic (AMPA/kainate) receptors and inhibits the GABAergic system, explaining the neurological effects, while high soluble oxalate drives oxalate nephropathy. The widely cited metabolic and anti-diabetic \"benefits\" come almost exclusively from in-vitro and rodent experiments; there are essentially no controlled human trials confirming any therapeutic effect. Overall the weight of human evidence is preliminary for benefits and clearer for risk. For most people with healthy kidneys, normal culinary amounts are considered safe and nutritious. Anyone with reduced kidney function or on dialysis should avoid it completely.

What is the typical dose of Starfruit (Carambola)?

1 medium fruit (~91 g) or ~100 g sliced; avoid entirely in chronic kidney disease

Is Starfruit (Carambola) safe? Any cautions or side effects?

CONTRAINDICATED in chronic kidney disease, end-stage renal disease, and dialysis patients—even a single fruit or glass of juice can trigger hiccups, vomiting, confusion, seizures, status epilepticus, and death (caramboxin neurotoxin plus oxalate nephropathy). Toxicity has also been reported with normal-to-moderate renal function, especially when consumed on an empty stomach, dehydrated, or in large quantity/concentrated juice. High oxalate content poses a kidney-stone risk in susceptible individuals and can cause acute oxalate nephropathy. Like grapefruit, starfruit inhibits CYP3A4 and can raise blood levels of interacting drugs (e.g. statins, certain calcium-channel blockers). If neurological symptoms appear after ingestion in a renal patient, urgent hemodialysis/hemofiltration is the recommended treatment.

How many studies support Starfruit (Carambola)?

NutriDex cites 10 sources for Starfruit (Carambola), graded "Preliminary".

Cite this page
APA

Peh, D. (2026). Starfruit (Carambola) (Averrhoa carambola): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/starfruit-carambola

BibTeX
@misc{nutridex_starfruit_carambola,
  author       = {Peh, Daryl},
  title        = {Starfruit (Carambola) (Averrhoa carambola): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/starfruit-carambola},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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