What Are the Benefits of Star Fruit?

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Story at-a-glance -

  • Star fruit, also known as carambola, is a tropical fruit native to Asia that is so-named because a star is revealed when this curious-looking oblong fruit is cut crosswise
  • This waxy green-yellow fruit is entirely edible and contains beneficial amounts of vitamin C, B vitamins, and antioxidant flavonoids such as epicatechin, gallic acid and quercetin
  • Star fruit preparations containing the fruit and leaves have long been used in Ayurvedic medicine for the treatment of diarrhea, fever, hemorrhoids, skin diseases, vomiting, worm infestations and other conditions
  • While star fruit is well tolerated by most people, due to its unique composition, you will want to avoid it if you take prescription drugs or have a kidney disorder

By Dr. Mercola

Star fruit is an exotic tropical fruit that you can easily grow in your yard if you live in a warm climate such as Florida, like I do. Don't lose heart if you live in a cooler climate because you can grow a star fruit dwarf variety in containers as discussed in the featured video.

One of the beautiful things about star fruit is its productivity. I get about nine to 10 harvests a year off my tree. I enjoy its tart, sour flavor, which can be described as a combination of apple, grape and citrus. Despite its curious oblong shape, there are a multitude of health benefits hidden beneath its thin waxy skin. Once you realize how good star fruit is for you, you might just want to try eating it.

What Is Star Fruit?

Star fruit (Averrhoa carambola), also known as carambola, is a tropical fruit native to Asia and is commonly found in countries such as India, Indonesia, Malaysia, the Philippines, Sri Lanka and Vietnam.1 It also can be grown in warmer climates elsewhere in the world. The fruit is so-named because a star is revealed when it is cut crosswise.

The fruit itself is firm and yellow to green in color. Its outer skin is slightly waxy, but entirely edible. Star fruit flesh is crunchy, fiberless and incredibly juicy, with a texture similar to grapes. Ripe star fruits are sweet, but not overwhelmingly so due to their tart, sour flavor. They are also known for their oxalic acid odor, which varies from strong to mild depending on the star fruit variety.

Star Fruit Nutrition Facts

According to the U.S. Department of Agriculture National Nutrient Database,2 star fruit is low in calories and a good source of vitamin C and B vitamins. Star fruit also contains small amounts of important minerals such as magnesium, phosphorus and potassium, as well as trace amounts of iron and zinc. The fruit along with its waxy peel provides 3 grams (g) of dietary fiber, which helps promote healthy digestion and prevent absorption of dietary low-density lipoprotein (LDL) cholesterol in your gut.

The vitamin C in star fruit acts as a powerful natural antioxidant and one serving provides 34.4 milligrams (mg), or 57 percent, of your daily requirement for this vitamin. Vitamin C also supports your body's immune system and protects against harmful, inflammation-causing free radicals. Furthermore, star fruit is rich in antioxidant flavonoids such as epicatechin, gallic acid and quercetin.3

Star Fruit Nutrition Facts

Serving Size: 3.5 ounces (100 g), raw
  Amt. Per
Serving
% Daily
Value*
Calories 31  
Calories from Fat 3  
Total Fat 0 g 1%
Saturated Fat 0 g 0%
Trans Fat    
Cholesterol 0 mg 0%
Sodium 2 mg 0%
Total Carbohydrates 7 g 2%
Dietary Fiber 3 g 11%
Sugar 4 g  
Protein 1 g  
Vitamin A 1% Vitamin C 57%
Calcium 0% Iron 0%

*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie intake.

Health Benefits of Star Fruit

Star fruit has been used medicinally for thousands of years, particularly in developing regions where people are more apt to rely on plant-based remedies for the treatment of health problems. According to a review on star fruit featured in the International Journal of Pharma Research & Review in 2013,4 it has been used widely in Ayurvedic medicine.

The study authors, representing BCDA College of Pharmacy & Technology in West Bengal, India, suggest star fruit preparations containing the fruit and leaves have been used in the treatment of "skin diseases, pruritus (itchy skin), worm infestations, diarrhea, vomiting, hemorrhoids, intermittent fever, excess perspiration and general debility. It is also used in traditional medicines in countries such as India, China, Philippines [and] Brazil for various ailments."5

Because star fruit is widely available in India and has a long history of medicinal use in that country, the research team was well-acquainted with star fruit's usefulness. They noted:6

"The phytoconstituents reported to be present in the plant are mainly flavonoids, alkaloids, tannins and saponins … Various parts of the plant have been explored, [suggesting] antioxidant activity, analgesic activity, anti-inflammatory activity, hypoglycemic activity, hepatoprotective activity, antimicrobial activity and anti-ulcer activity. So, from the current review of literature and the ayurvedic texts, it can be concluded that [star fruit has a] high medicinal value."

According to the Ayur Times, star fruit is embraced within Ayurvedic medicine. Below are some of star fruit's purported medicinal uses:7

Boiled star fruit flowers are believed to be useful in the treatment of dermatitis, fever and malaria

Crushed star fruit leaves are reportedly applied externally to treat chickenpox and ringworm

Star fruit juice or tea prepared from the leaves has been shown to reduce blood pressure and blood sugar levels

Star fruit leaf extract is said to provide relief from angina and gastritis

Star fruit roots are suggested for headache and muscle pain relief, whereas powdered seeds are thought to be useful for soothing asthma attacks

The fruit, or a decoction of crushed starfruit seeds, is believed to increase breast milk production in lactating women

The ripe fruit or fruit juice has supposed antidiarrheal effects and is believed to stimulate your appetite

Additionally, a 2011 study8 highlighted the anti-inflammatory properties of star fruit with respect to the treatment of skin disorders on lab mice. The study authors said their research does "support the popular use of [star fruit] as an anti-inflammatory agent and opens up new possibilities for its use in skin disorders."

How to Cut and Use Star Fruit

Due to its curious oblong shape, green-yellow coloring and the waxy feel of its skin, some people are confused about how to eat star fruit. Actually, the waxy layer is quite thin and completely edible. As demonstrated in the video above, once you wash the fruit, cutting it couldn't be easier. Follow these three easy steps:

  1. Use a sharp knife to remove the ends
  2. Trim away the unripe green edge along each side of the star
  3. Cut the star fruit crosswise in quarter-inch chunks

There are many ways to enjoy star fruit.9,10 You can eat it raw, pair it with mint or infuse it into your drinking water. It's also a nutritious addition to shakes and smoothies. Due to its tart flavor, star fruit is popular in curries, desserts, chopped salads, fruit salads, jams, marmalades and savory dishes.

You may also find star fruit dried and sweetened as a candy, which I recommend you avoid due to its extremely high sugar content. Star fruit is also used as a garnish for cocktails. According to the horticulture and landscape architecture department at Indiana's Purdue University, star fruit has a wide variety of uses worldwide, including:11

Australians cook the sweeter type of green star fruit as a vegetable

Filipinos use star fruit juice as a seasoning

Chinese serve star fruit alongside fish and pack them in syrup for export

Hawaiians use juice from sour star fruit to make sorbet by combining it with boiling water, gelatin, lemon juice and sugar

Jamaicans sometimes dry ripe star fruit

Malaysians stew star fruit with cloves and sugar or combine it with apples

Thais slice green star fruit and boil it with shrimp, whereas they salt and pickle slightly underripe star fruits to make jam or other preserves

Cautions About Star Fruit

While star fruit is a nutrient-rich fruit known for its many health benefits, like any fruit I recommend you eat it only occasionally. Be sure to keep your total fructose intake below 25 g daily, including fructose from whole fruit. If you have diabetes, heart disease, high blood pressure or insulin resistance you should limit your daily intake of fructose to 15 g until your condition improves.

In addition to watching your fructose intake, keep in mind star fruit can be harmful, and even lethal, under certain conditions. The major cautions about star fruit are as follows:12

Allergies: Though uncommon, allergies to star fruit are possible, so be sure to try only a small amount on your first occasion of eating it. Certainly, if you experience digestive upset, diarrhea, nausea or vomiting after eating star fruit, you will want to avoid it in the future.

Drug interactions: Star fruit is one of several fruits — grapefruit, pomelo and Seville orange are others — flagged for its potential to interfere with your body's ability to metabolize certain drugs.13 Because this inhibitory action can be dangerous, particularly if you are taking multiple prescriptions, be sure to check with your doctor before consuming star fruit if you have concerns about potential drug-related effects.

Kidney stones: While generally safe for most people, the U.S. National Kidney Foundation says star fruit, due to its very high concentration of oxalic acid, cannot be safely processed if you suffer from kidney disease.14 Oxalic acid contributes to the formation of kidney stones.

A 2015 study15 suggests you avoid eating star fruit if you suffer from chronic kidney disease or are on dialysis. Researchers noted even individuals with healthy kidneys should take care to not overconsume star fruit given the possibility of developing kidney problems from excessive or prolonged consumption.

Toxicity: Certain compounds in star fruit are known to be dangerous, and even deadly, unless your kidneys process them out of your body. If after eating star fruit you experience confusion, headaches, nausea or seizures, you may be suffering from acute star fruit toxicity. Because star fruit toxicity can be life-threatening, you should seek medical attention immediately.

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