Star Fruit (Carambola): Nutrition, Benefits and Kidney Warning

Star fruit, or carambola (Averrhoa carambola), is the waxy, yellow-green fruit that falls into perfect five-pointed stars when you slice it. It’s native to Southeast Asia and is now grown across the tropics, including Florida, Hawaii, Brazil, India and Malaysia. The whole fruit is edible, skin included, and it tastes like a cross between apple, grape and citrus, ranging from sweet to quite sour depending on the variety.

This guide covers star fruit nutrition, its health benefits, the serious kidney warning, and how to choose and eat it safely. For more tropical fruits, see our fruit guides.

Star fruit nutrition facts

Star fruit is mostly water, which keeps it very low in calories and sugar. Its main nutrient is vitamin C. The table below uses USDA values for raw star fruit.

Source: USDA FoodData Central — Carambola (starfruit), raw (SR Legacy, FDC ID 171715). % Daily Value (DV) uses FDA values for a 2,000-calorie diet.

One medium star fruit gives about 31 mg of vitamin C, roughly a third of the daily value, plus 2.5 grams of fiber, for just 28 calories and under 4 grams of sugar. That makes it one of the lowest-sugar tropical fruits you can buy, with fewer calories than an apple of the same weight.

A cup of cubed star fruit (132 g) has about 41 calories, 45 mg of vitamin C and 3.7 grams of fiber. It’s also a modest source of copper, which helps your body make red blood cells and use iron.

Health benefits

For people with healthy kidneys, star fruit’s benefits come from its nutrients and its low calorie count. Each finding below carries an evidence label, explained in our editorial policy.

Vitamin C for immunity and skin Strong evidence

Vitamin C supports your immune system, helps wounds heal and is needed to make collagen for skin, cartilage and blood vessels. It also boosts absorption of iron from plant foods such as beans and leafy greens, so star fruit is a good addition to a plant-based meal.

Fiber for digestion Strong evidence

Most of star fruit’s fiber is insoluble, the kind that adds bulk to stool and helps keep you regular. Diets rich in fiber from fruit, vegetables and whole grains are linked to lower risks of heart disease, type 2 diabetes and bowel cancer.

Weight management Moderate evidence

Fruits that are high in water and fiber and low in calories, like star fruit, help you feel full on fewer calories. Swapping sweets or chips for fruit is a simple way to lower your overall calorie intake.

Antioxidants Limited evidence

Star fruit contains polyphenols, including proanthocyanidins and epicatechin, which show antioxidant activity in the lab. Whether eating star fruit gives meaningful antioxidant benefits in people hasn’t been studied.

Cholesterol and blood sugar Limited evidence

Some animal studies report that star fruit fiber or extracts lowered cholesterol or blood sugar. These effects haven’t been tested in human trials, so they’re not a reason to eat it.

The kidney warning: who must avoid star fruit

Star fruit is unusual among everyday fruits because it can be dangerous to a specific group of people. Healthy kidneys filter out its toxins. When the kidneys don’t work well, those toxins build up in the body and can reach the brain.

The main culprit is caramboxin, a toxin identified in 2013 that acts on glutamate receptors in the brain and overstimulates nerve cells. Star fruit is also very high in oxalate, which can form crystals that block and damage the tiny tubes in the kidneys. Sour varieties contain more oxalate than sweet ones.

Symptoms can start within hours of eating star fruit or drinking its juice, and in some cases after eating just one or two fruits. There’s no known safe amount for people with reduced kidney function.

Get emergency help if you or someone with kidney disease develops hiccups that won’t stop, vomiting, confusion, weakness, numbness or seizures after eating star fruit. Tell the medical team about the star fruit, as doctors may not think to ask. See also our medical disclaimer.

Is star fruit safe for healthy people?

For people with normal kidney function, eating a star fruit or two as part of a varied diet is considered safe. Problems in healthy people are rare and have generally involved unusually large amounts.

Case reports describe acute kidney injury, sometimes with nerve symptoms, in people with previously normal kidneys who ate a very large number of star fruits or drank large amounts of concentrated star fruit juice, often on an empty stomach or while dehydrated. In one 2020 case report, a 51-year-old man developed kidney injury and weakness after eating more than 50 star fruits. Most of these people recovered, but some needed dialysis.

To keep risk low:

• Stick to one or two fruits at a time, not several in a row.
• Eat star fruit with or after a meal rather than on an empty stomach.
• Avoid drinking large amounts of pure star fruit juice, which concentrates the oxalate.
• Drink enough water, especially in hot weather or after exercise.
• Choose sweeter varieties if you eat it often, as they contain less oxalate.

Star fruit and medicines

Lab studies suggest star fruit may block some of the same liver enzymes as grapefruit, which help the body break down many medicines. That could, in theory, raise levels of certain drugs in your blood. This hasn’t been well studied in people, but if your medicine comes with a grapefruit warning, it’s sensible to ask your pharmacist about star fruit too.

How to choose and eat star fruit

• Choosing: look for firm, shiny fruit that’s mostly yellow with only a hint of green. Brown edges on the ridges are normal on ripe fruit. Avoid fruit with soft, brown patches.
• Ripening: green star fruit will ripen at room temperature in a few days. Once ripe, refrigerate it and eat it within about a week.
• Preparing: rinse it, trim off the dark edge of each ridge if you like, then slice it crosswise into stars. Pick out the small seeds.
• Eating: eat it raw, add slices to fruit salads and green salads, or use it as a garnish for drinks and desserts.
• Cooking: in Southeast Asia and India, sour star fruit is cooked into chutneys, pickles, jams and curries.

In the US, most star fruit comes from Florida and Hawaii, with imports from Central America and Asia filling the gaps. Florida fruit is in season from late summer through winter, which is when it’s cheapest and tastiest. Because the fruit bruises easily along its ridges, it’s often picked slightly green and shipped to ripen at home. A ripe star fruit smells lightly floral; if it has no scent and is still mostly green, give it a few more days on the counter.

Looking for other low-calorie, high-vitamin C fruits that suit everyone, including people with kidney disease who are allowed fruit? Ask your dietitian about apples, berries and pineapple, which are lower in potassium and oxalate.

More guides you may find useful: low-sugar fruits.

Star fruit FAQ