Nutritional Benefits Of Star Fruit For Overall Health

Introduction to star fruit 

The star fruit plant, also known as Averrhoa carambola, is a plant that grows naturally in South and South-East Asia (namely in India, Bangladesh, Philippines, Indonesia, Malaysia, Vietnam, and Sri Lanka).¹ Though it is also widely consumed in the United States, Australia, and the South Pacific Islands. The taste of the fruit varies from very sour to sweet depending on how ripe the fruit is and whether it is of the sweet variety (with 5% sugar content) or of the tart variety (with 1% acid content).² The fruit is yellow in appearance (when ripe and green when unripe) and when sliced it has a 5-point star like appearance hence the name.³ It is also commonly used in traditional Chinese medicine and in Ayurvedic remedies, though there is not a lot of scientific backing for such uses. Additionally, it can also be used to clean utensils as it is able to remove rust.³

Nutritional profile of star fruit 

Star fruits are rich in naturally occurring vitamins and minerals, which contribute to the various health benefits associated with their consumption. Though star fruit should be consumed in moderation, there is some debate over how much star fruit can be consumed before the health benefits are outweighed by the potential neurotoxic and nephrotoxic effects.

Rich source of vitamin C 

Star fruit is naturally rich in vitamin C, with an average content of around 25.8 mg of vitamin C per 100 g of star fruit consumed.³ The NHS recommends that the average adult (aged 19 to 64) requires around 40 g of vitamin C per day. This is not stored in the body and needs to be acquired through your diet. Vitamin C is required to maintain healthy bones, cartilage skin and blood vessels. It also contributes to healthy wound healing and to protect your cells.

Dietary fibre content 

Star fruit has a high amount of insoluble fibre per fruit (around 0.8g of fibre per fruit).² Insoluble dietary fibre is important as it can retain water content, which allows it to lower blood glucose levels by slowing down the absorption of carbohydrates. It also aids in smooth bowel movement. Additionally, it also contributes to lowering the body’s cholesterol levels.³ 

Antioxidant properties 

Starfruit has some antioxidants present, including vitamin C and gallic acid. It also contains proanthocyanidins (a chemical compound found in many fruits like cranberries and blueberries). This contributes to the removal of toxins from the body and helps to prevent oxidation damage from the toxins that may lead to cancer.³ 

Hypoglycemic effect 

The high insoluble fibre content in the star fruit contributes to the delay in the release of glucose from starch. This can contribute to the decrease in blood sugar levels. There have been several studies conducted with animal subjects to demonstrate the positive effect on blood sugar levels (Ferreira et al) and possible links to reducing blood sugar levels in diabetic patients. However, further clinical studies are required in this area to establish any possibilities for future treatments utilising star fruit.¹ 

Anti-inflammatory properties 

There is some limited evidence relating to star fruit having anti-inflammatory properties. In traditional medicine, it is used to treat skin conditions like eczema but there is little evidence to support this. However, a study by Cabrini et al showed some promising results; the study showed that ethanolic extracts from star fruit can gradually reduce inflammation and eczema in mice. ³ While further research is required into this area, it does show some potential in future treatment options for conditions like eczema.

Heart health benefits 

There is some limited evidence in regard to the star fruit being able to reduce blood pressure. A reduction in blood pressure can contribute to overall improved cardiovascular health, though there is not a lot of research conducted in this area. Most of the studies have shown potential, but as they were on animal subjects, the results cannot be directly applied to humans.¹

Minerals for bone health 

Starfruit is high in many different vitamins and minerals.² This includes

• Iron
• Vitamin B
• Vitamin C
• Oxalate 
• Potassium 

These minerals can increase the mineral bone density and potassium has been linked to better bone health by decreasing the risk of fractures and conditions such as osteoporosis.⁴

Weight management and digestive health 

The high fibre content and positive effects on blood sugar can contribute to weight loss when combined with a balanced diet and regular exercise. It has also been linked to the removal of cholesterol in the body.¹ Though star fruit alone is not responsible for weight loss. 

Though there is extremely limited research in this area, consuming star fruit in moderation can also be helpful for digestive health. The high fibre content is responsible for smooth bowel movements and can help you to reach the daily recommended amount of dietary fibre. However, excessive consumption of star fruit is not recommended due to possible associated health risks. 

Cautionary notes and considerations 

While star fruit has many health benefits, there are some concerns that need to be noted. It is recommended that individuals who suffer from chronic kidney disease or kidney failure should exercise caution regarding consuming star fruit as it has been known to be nephrotoxic (cause damage to the kidneys) and neurotoxic (cause damage to the brain and nervous system). 

The nephrotoxic properties of star fruit are thought to be from the high oxalate content, while the neurotoxic properties are from carambola.¹ As people with renal issues have impaired kidney function, they are unable to filter toxins from their diet. This means that consuming the star fruit or undiluted star fruit juice can lead to poisoning. Typical star fruit poisoning symptoms include:⁵ 

• Hiccups 
• Vomiting 
• Mental confusion 
• Nausea 
• Loss of consciousness 

This can be worsened by consuming star fruit in excessive amounts or by consuming it on an empty stomach. In some cases, it has been known to cause poisoning in those without any renal conditions, but this is not as common.⁵  

The best course of treatment for such poisoning is haemodialysis. Other forms of treatment do not significantly help with improving any of the above symptoms.⁶ 

Incorporating star fruit into the diet 

Star fruit can be described as sweet when ripe, with a texture similar to that of grapes. They can be consumed in numerous ways depending on local recipes. For example: 

• The fruit can be eaten whole since the peel is also edible and has some nutritional value.  
• In some parts of the world, it is common for it to be sliced and eaten with some spices or black salt as the sweet and salty flavour combination is quite popular in different regions.  
• Some recipes call for the star fruit to be cooked as a vegetable.  
• In some places, the star fruit is pickled or turned into a jam.  
• The sour variety of star fruit is popular for making cold drinks, and in some countries, it is sold as bottled juice.  

Summary

Star fruit is a popular fruit that is grown in tropical regions but enjoyed in many parts of the world. There is a surprising amount of health benefits associated with consuming star fruit. This is due to its nutritional content, which includes a high amount of insoluble fibre and high vitamin and mineral content. It has been used for a long time in traditional remedies in Ayurvedic and traditional Chinese medicine, but these claims have not been scientifically proven. However, the limited number of clinical studies that have been conducted does show the potential for star fruit to be used beneficially in medicine.

Starfruit has been shown to have some good antioxidant effects, anti-inflammatory properties, and a hypoglycaemic effect, amongst other health benefits. It is important to note that people with kidney disease are concerned about the consumption of star fruit. The impaired kidney functions in kidney disease make it difficult for the body to filter out any nephrotoxic and neurotoxic chemicals that are naturally present in the fruit. This has led to cases of poisoning that require dialysis to treat it.