In recent years, kiwi has transformed from a Chinese ornamental plant into a crop of global nutritional importance, thanks to growing consumer interest in superfoods and the potential of natural dietary supplements to improve health. The scientific literature has proven that kiwi is particularly rich in vitamin C with high bioavailability, making it an excellent food for improving health in several ways.
Numerous studies and meta-analyses have shown the effectiveness of kiwi in improving the digestive system, and particularly in relieving constipation. It contains a lot of fiber, substances that help store water in the body, and the proteolytic enzyme actinidin, which are known to improve the body's ability to digest protein. Experts recommend consuming kiwi to strengthen the immune system in the body.
There are two common types of kiwi in the world – yellow kiwi and green kiwi. Their cultivation is concentrated in China, New Zealand, Italy, and Greece, and these four countries together account for about 85% of global kiwi crop production as of 2022. The scientific world increasingly supports the role of kiwi as a "functional food," emphasizing the many physiological benefits of the fruit beyond basic nutrition.
The nutritional profile
Studies have shown that a small 100-gram serving of green kiwi contains about 65 calories and about 58.8 mg of vitamin C (peeled green kiwi, values vary depending on the variety and the peel). This small serving exceeds the recommended daily intake of vitamin C, proving that kiwi contains unexpectedly high concentrations of essential micronutrients.
Studies confirm that vitamin C derived from kiwi has high bioavailability, and the fruit contains about 2.1 grams of dietary fiber per 100 grams without the peel (and if you decide to eat the peel as well, then more). It contains about one-third soluble fiber and two-thirds insoluble fiber, a mixture with a particularly high water-holding capacity, which beneficially affects the functioning of the digestive system.
Kiwi additionally provides other key micronutrients, including potassium and folic acid, alongside vitamin E and vitamin K. Furthermore, biochemical studies and human trials have revealed that kiwi is a unique source of bioactive actinidin, a natural protease enzyme that remains active in the acidic environment of the stomach and is currently known to improve the digestion of proteins – and helps reduce bloating.
The benefits to the digestive system
The strongest clinical evidence shows the positive effects of kiwi on overall digestive system function. A 2024 systematic review and meta-analysis investigating the benefits of kiwi confirmed that the fruit significantly improves normal bowel activity in adults suffering from functional constipation.
Similarly, randomized controlled human trials have shown that consuming two kiwi fruits daily can effectively improve symptoms in patients with functional constipation, and in some trials, also irritable bowel syndrome (IBS).
Immune system health
Kiwi consumption can strengthen the immune system, mainly due to the high concentration of highly bioavailable vitamin C in the fruit. Daily consumption of kiwi will not necessarily reduce the incidence of various illnesses, but studies have demonstrated a significant reduction in the severity of head congestion and sore throat symptoms and in their duration following regular kiwi consumption. The study linked the observed benefit to a significant increase in plasma vitamin C levels of the participants following consistent kiwi consumption.
<br>Additional potential health benefits
The benefits of vitamin C and dietary fibers found in kiwi are well-documented, but studies in other areas show promising yet more preliminary findings in additional fields:
Antioxidant and anti-inflammatory effects
Beyond vitamin C, kiwi has varying concentrations of vitamin E, carotenoids, and polyphenols, which are powerful antioxidants that help protect cells from oxidative stress and DNA damage. Furthermore, preliminary findings indicate that frequent consumption of kiwi may help reduce low-grade inflammation, which is an underlying factor in many chronic diseases such as cardiovascular diseases and even certain types of cancer.
Improving sleep quality
Emerging research indicates that kiwi may help improve sleep quality, with one small study finding that consuming two kiwis an hour before bedtime consistently for 4 weeks reduced the time it takes to fall asleep by about 35%.8. Kiwi consumption was also linked to reduced wake time and increased total sleep time (about 13%), likely due to the antioxidant and serotonin content in the fruit.