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Star fruit, also called carambola (Averrhoa carambola), is a crisp, juicy tropical fruit that forms a five-pointed star when sliced. One medium star fruit has only about 28 calories and supplies about 35% of the Daily Value for vitamin C, according to USDA data. It also carries a serious caution: star fruit contains oxalate and a nerve toxin called caramboxin, and published case reports link it to kidney injury and neurological symptoms, mostly in people who already have kidney disease. Below are the USDA star fruit nutrition facts, the realistic star fruit benefits, and what the medical literature says about star fruit toxicity.
Peptide Labs does not sell star fruit or star fruit products. This article is general nutrition information, not medical advice.
Key Takeaways
- One medium star fruit (91 g) has about 28 calories, 2.5 grams of fiber and 35% of the Daily Value for vitamin C in USDA data.
- A cup of cubes has about 41 calories and 5.3 grams of natural sugar, among the lowest of common fruits.
- Star fruit contains oxalate and caramboxin; case reports link it to acute kidney injury, hiccups, confusion and seizures.
- About 7 in 10 published cases involved people with existing kidney problems, but cases also occurred in people with normal kidney function, often after concentrated juice or eating on an empty stomach.
- If you have kidney disease or are on dialysis, ask your kidney care team before eating any star fruit.
Star fruit nutrition per fruit and per cup
The table uses the USDA FoodData Central SR Legacy entry for raw carambola (FDC 171715), converted to USDA’s portion weights for one medium fruit about 3.6 inches long (91 grams) and one cup of cubes (132 grams). The percent Daily Value (%DV) uses the FDA Daily Values printed on Nutrition Facts labels.
| Nutrient (raw star fruit) | 1 medium (91 g) | % DV | 1 cup cubes (132 g) | % DV |
|---|---|---|---|---|
| Calories | 28 | Not applicable | 41 | Not applicable |
| Carbohydrate | 6.1 g | 2% | 8.9 g | 3% |
| Fiber | 2.5 g | 9% | 3.7 g | 13% |
| Total sugars | 3.6 g | No DV | 5.3 g | No DV |
| Protein | 0.9 g | 2% | 1.4 g | 3% |
| Vitamin C | 31 mg | 35% | 45 mg | 50% |
| Copper | 0.13 mg | 14% | 0.18 mg | 20% |
| Potassium | 121 mg | 3% | 176 mg | 4% |
| Folate | 11 mcg DFE | 3% | 16 mcg DFE | 4% |
| Magnesium | 9 mg | 2% | 13 mg | 3% |
Star fruit is about 91% water in USDA data, which explains the low calorie count. Its nutrient highlights are vitamin C and copper, a trace mineral, with a useful amount of fiber for so few calories. It is lower in vitamin C than strawberries or kiwi per serving, as our guide to vitamin C sources shows, but it is still a meaningful contributor.
Star fruit compared with other fruits
On sugar and calories, star fruit sits at the low end with berries, which is why it often appears on low-sugar lists; our guide to fruit sugar levels covers that comparison in detail. The table compares a typical serving of each fruit.
| Fruit (USDA FDC ID) | Serving | Calories | Total sugars | Fiber | Vitamin C (% DV) |
|---|---|---|---|---|---|
| Star fruit (171715) | 1 cup cubes, 132 g | 41 | 5.3 g | 3.7 g | 45 mg (50%) |
| Strawberries (167762) | 1 cup whole, 144 g | 46 | 7.0 g | 2.9 g | 85 mg (94%) |
| Green kiwi (168153) | 1 fruit, 69 g | 42 | 6.2 g | 2.1 g | 64 mg (71%) |
| Pineapple (169124) | 1 cup chunks, 165 g | 83 | 16.3 g | 2.3 g | 79 mg (88%) |
| Apple with skin (171688) | 1 medium, 182 g | 95 | 18.9 g | 4.4 g | 8 mg (9%) |
| Jackfruit (174687) | 1 cup sliced, 165 g | 157 | 31.5 g | 2.5 g | 23 mg (25%) |
For more detail on the comparison fruits, see our guides to strawberries and kiwi, and our sibling guide to jackfruit, a far sweeter and more filling tropical fruit.
Star fruit and kidney disease: the key caution
Star fruit is one of the few everyday fruits with a well-documented toxicity problem. Two substances are involved. The first is oxalate (oxalic acid), which can form crystals in the kidney tubules. The second is caramboxin, a molecule identified in 2013 by Brazilian researchers in a study published in Angewandte Chemie, who described it as the compound behind the neurological symptoms seen in people with chronic kidney disease who ate star fruit. Caramboxin acts on glutamate receptors and blocks calming GABA signals in the brain, which shifts the nervous system toward overexcitation.
- 2021 review of 136 cases: a narrative review of 10 case series and 28 case reports found that 94 of 136 people (69%) had kidney impairment before eating star fruit. Kidney biopsies showed acute oxalate nephropathy, and neurological effects ranged from persistent hiccups to prolonged seizures. Dialysis improved outcomes for the neurological symptoms.
- Normal kidney function does not rule it out: about 3 in 10 people in that review did not have known kidney problems. The first two cases of acute oxalate nephropathy, reported from Taiwan in 2001, followed large quantities of sour carambola juice; both people needed dialysis before their kidney function recovered about 4 weeks later.
- Concentrated juice and home remedies: a 2018 Sri Lankan case series described three people with diabetes who developed acute kidney injury after using star fruit as a remedy, and a 2022 case described a 78-year-old man without prior kidney disease who drank homemade concentrated juice for a week. The 2018 authors said star fruit should be discouraged as a diabetes remedy.
- Risk factors named in the reports: eating star fruit or drinking the juice on an empty stomach or while dehydrated, and pure fresh or lightly diluted sour juice, which contains more oxalate than commercial juice made by pickling and dilution.
Symptoms described in star fruit toxicity reports include hiccups, nausea, vomiting, abdominal or back pain, weakness, confusion and seizures, sometimes starting within hours. Anyone with these symptoms after eating star fruit needs emergency care, and should tell the care team about the star fruit.
Who should be careful with star fruit
- People with kidney disease or on dialysis: most published cases involved reduced kidney function, so ask your nephrologist or kidney dietitian before eating any star fruit or star fruit juice.
- People told to limit oxalate: if a clinician has advised a lower-oxalate eating pattern, ask before eating star fruit; our oxalates guide explains what oxalate is.
- Anyone using star fruit as a remedy: concentrated juice made at home appears repeatedly in the case reports. Star fruit is a food, not a blood sugar remedy; talk to your clinician about diabetes care.
- Everyone else: the reported cases are rare compared with how widely star fruit is eaten, but eating it with a meal and staying hydrated matches the risk factors the case authors describe.
Star fruit benefits: a realistic view
Human research on star fruit as a food is thin. Many online star fruit benefits lists draw on lab and animal studies of leaf or fruit extracts, which do not show what eating the fruit does in people, and the case literature shows that heavy use as a remedy carries real risk. What the USDA data do support is that star fruit is low in calories and sugar, provides fiber, vitamin C and copper, and adds water and crunch to fruit salads. Fruits like this fit an eating pattern rich in plants, and if you are eating smaller portions on a GLP-1 medicine, our GLP-1 diet guide covers how low-calorie fruits fit in. For people without kidney concerns, star fruit can simply be one fruit among many.
Frequently Asked Questions
What does star fruit taste like?
Sweet varieties taste mildly sweet and tart, somewhere between apple, grape and citrus. Sour varieties are much more acidic and are the type most often used for juice.
How many calories are in a star fruit?
About 28 calories in one medium star fruit and about 41 in a cup of cubes, in USDA data.
Is star fruit bad for your kidneys?
It can be. Star fruit contains oxalate and caramboxin, and case reports link it to acute kidney injury, mostly in people with existing kidney disease. If you have kidney disease, ask your kidney care team before eating any.
What are the symptoms of star fruit toxicity?
Reported symptoms include hiccups, nausea, vomiting, weakness, confusion and seizures. Seek emergency care and mention the star fruit.
Is carambola the same as star fruit?
Yes. Carambola is another name for star fruit, Averrhoa carambola.
What are the main star fruit benefits?
USDA data show star fruit is low in calories and sugar and provides vitamin C, fiber and copper. Human research on other health effects is limited.
Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before starting a supplement, especially if you take medicines, are pregnant, have kidney disease or have a food allergy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed October 2026.
Related guides: Jackfruit: USDA Jackfruit Nutrition, Meat Substitute Facts and Allergy, Oxalates: High Oxalate Foods, Low Oxalate Foods and Kidney Stones, Low Sugar Fruits: USDA Sugar per Serving, From Lowest to Highest.