Introduction 

Antioxidants are significant in achieving healthy and glowing skin. The potent compounds of antioxidants are essential in neutralising free radicals and external pollution, supporting the skin barrier. Among many foods rich in antioxidants, star fruit, also known as Carambola, is one of the strong contenders for providing nutrients for healthy skin. Filled with nutrients and a diverse array of antioxidants, star fruit has the potential to enhance skin vitality.¹ So, let’s dive deep into how star fruit provides antioxidant properties to attain healthy skin. 

Understanding antioxidants 

Our skin faces external environmental factors such as UV radiation, pollution, and chemical damage that produce free radicals and reactive oxygen species (ROS). This phenomenon is called oxidative stress. Excessive oxidative stress can lead to the deterioration of the skin barrier, extrinsic skin damage and ageing. Other lifestyle factors such as inadequate nutrition, mental and physical stress, intake of alcohol, and overeating also contribute to poor skin health. Among these factors, 80% of the skin damage is caused by UV radiation and subsequent production of ROS and oxidative stress.²

The skin has various exogenous and endogenous antioxidant defence mechanisms to combat oxidative stress and neutralise the molecules. Therefore, antioxidants protect the skin barrier and improve skin vitality. Moreover, they can also provide a wide range of benefits, such as reduced inflammation, increased collagen production and improved skin texture.³

Star fruit: A nutrient powerhouse

Star fruit, also known as the Carambola, belongs to Averrhoa Carambola. The fruit has 5-6 ridges and derives its name from its unique shape resembling a star when sliced in cross-section. The star fruit is native to Southeast Asia but is now cultivated in tropical regions worldwide. The texture is crispy, and it has a sweet and tangy flavour.⁴ 

Nutritional composition of star fruit 

According to FoodData Central, star fruit is low in calories but high in dietary fibre, making it a healthy fruit. It is also a rich source of vitamins, minerals, and antioxidants, such as vitamin C and gallic acid; and beta-carotene. 

100 g of star fruit contains:

• 31 calories
• 1.04 g of protein
• 6.73 g of carbohydrate
• 2.8 g of fibre
• 3 mg of calcium
• 10 mg of magnesium
• 133 mg of potassium
• 2 mg of sodium
• 34.4 mg of vitamin C
• 12 mg of phosphorus
• 25 µg of beta carotene

Benefits of antioxidant-rich star fruit for skin 

Skin hydration and moisture retention

One of the primary benefits of incorporating antioxidant-rich star fruit into your skincare routine is its ability to promote skin hydration and moisture retention. The high water content of star fruit, coupled with antioxidants like vitamin C, is beneficial in maintaining the skin's optimal hydration. The skin barrier performs its protective functions better when it is appropriately moistened, and the hydro-lipid layer is balanced. Moreover, hydrated skin is more resilient and prone to dryness and flakiness while giving a radiant and healthy skin appearance.⁵

Reduction of oxidative stress and premature ageing

The antioxidants in star fruit are a crucial major contributing factor in skin cancers and ageing.² Antioxidants in star fruit can neutralise free radicals, thereby reducing oxidative stress and protecting skin cells from damage. Therefore, they can also prevent the formation of fine lines, wrinkles, and other signs of ageing. Moreover, star fruit extract is emerging as the new ingredient for skin-care products targeting to achieve a youthful and revitalised complexion.

Promotion of collagen synthesis for skin elasticity

Vitamin C, a prominent antioxidant in star fruit, is known for its role in collagen synthesis. Collagen is a protein that maintains skin elasticity and firmness. With ageing, collagen production slowly declines, leading to sagging and loss of skin elasticity. Vitamin C in star fruit promotes the transcription of collagen synthesis and is commonly used in skin-care products to improve skin elasticity in young and aged skin.⁶ 

Improvement of overall skin tone and texture

Antioxidant-rich star fruit can improve overall skin tone and texture. The combination of vitamins, minerals, and antioxidants in star fruit helps brighten the complexion, reduce uneven skin tone, and enhance the skin's texture. Due to the anti-inflammatory properties of vitamin C, it is also helpful in wound healing and reducing skin redness.⁶ Star fruit can be a valuable ally in achieving a radiant and smooth skin surface, whether consumed as part of a balanced diet or applied topically in skincare routines.

Incorporating star fruit into your skincare routine

There are various ways to incorporate star fruit into a balanced diet or skincare routine to obtain the beneficial effects of antioxidants and achieve a healthy and glowing complexion. 

Inclusion of star fruit in the diet for internal benefits

Before ingesting a star fruit, first check the colour of the fruit. Ripe star fruits are yellow, the more vibrant the colour, the sweeter the fruit. Firstly, wash the fruit with clean water to remove dirt and contaminants. The skin is also edible, and only the tiny seeds in the middle need to be removed. Then, cut the fruit into thin slices and remove the edges. The fruit can be eaten as it is or made into juices. Star fruit can be mixed with other nutrient-rich fruits, such as oranges and berries, and added to smoothies to boost antioxidants. It can also be put into salads and dishes for a unique taste.

DIY star fruit face masks and skincare recipes

To create DIY face masks, mash star fruit into a paste and apply it on the skin for 15-20 minutes before rinsing. The antioxidants in the star fruit can provide hydration and rejuvenate the skin. Another way of incorporating star fruit into skincare is mixing the fruit extract with water and using it as a toner. This toner can be applied to the skin with a cotton pad to hydrate and prepare the skin for subsequent skincare steps. 

Commercial skincare products featuring star fruit extract

Many skincare products contain star fruit extract. These can include cleansers, moisturisers, toners, and serums, which provide the beneficial properties of antioxidants. Sheet masks with star fruit extract provide overnight hydration to promote skin vitality. Since antioxidants in star fruit are effective against UV radiation, star fruit extract is also a common ingredient in sunscreen. 

Precautions and considerations 

Although star fruit is delicious and beneficial for skin health, overeating or unripe fruit can have side effects on the body. A case of oral allergy syndrome was reported after eating a star fruit.⁷ This can manifest in the mouth, throat or lips as itching or swelling after eating. Therefore, individuals with a previous food allergy history should consult a doctor before eating the fruit. The condition of the fruit needs to be checked before ingestion. It is best to be eaten when ripe. Unripe star fruit is green and can taste sour, potentially irritating the mouth and throat. Moreover, the seed in the centre of star fruit is not recommended to be eaten. So, please make sure to remove it before eating. 

Since star fruit is a rich source of oxalate, ingesting a large amount can cause kidney stones and kidney injury.⁸ Therefore, patients with kidney disease should not eat star fruit. Individuals with an active medication should consult with the health care providers before the ingestion of star fruit due to its potential interaction with the drugs. In addition, pregnant or nursing individuals should seek advice from their healthcare provider before introducing significant changes to their diet, including incorporating star fruit. While it is generally safe, individual health conditions and considerations may vary. Patients with diabetes, liver conditions, or other chronic health issues also should consult with a doctor before eating star fruit. The fruit's natural sugars and oxalate content may need to be monitored for specific medical conditions.

Summary 

Starfruit contains many nutrients and antioxidants, including vitamin C and beta-carotene. Since the skin barrier is continuously attacked by external pollutants such as UV radiation and free radicals, oxidative stress is produced. Antioxidants are crucial for combating oxidative stress and protecting the skin. They are essential in maintaining the skin's vitality and slowing ageing. Ingestion of star fruit can provide a variety of antioxidant properties for the skin and achieve a healthy complexion.2 There are many ways to eat star fruit, either by itself or by making it into delicious smoothies with other fruits. It is also an active ingredient in many skincare products, such as sunscreen, to protect against UV radiation. Although it is, star fruit should be eaten cautiously by individuals with a previous drug or medical history.