Scientific Name(s): Actinidia chinensis Planchon.
Common Name(s): China gooseberry, Chinese gooseberry, Kiwi fruit, kiwi fruit extract, Tara fig, Tengligen
A. chinensis, the plant source of kiwi fruit, is native to China and Taiwan, but cultivation is widespread throughout the world. Major producers include New Zealand, the United States (California), and Italy, but a considerable harvest is obtained from several other countries, including France, Israel, and Spain. The Hayward variety is the most commonly grown commercial cultivar because of its superior hardiness and long shelf life, but several other varieties, including one bearing a yellow-fleshed fruit, are cultivated. The plant is a vigorous, deciduous climber that grows to about 9 m in height, tolerating full sun or semishade. The scented flowers are pollinated by insects and appear in summer. Individual flowers are dioecious, with male or female flowers on separate plants. The egg-shaped fruit has a furry, brown skin, and firm, translucent, emerald-green flesh with numerous small, edible, black seeds at the center. When ripe, the fruit is very juicy with an acidic flavor, often described as a mixture of strawberry and pineapple. "Tara fig" (Actinidia arguta) is a related American species grown domestically.1, 2, 3, 4
The fruit was originally known as the Chinese gooseberry, but after aggressive marketing by New Zealand fruit growers, it became known as the kiwi fruit, partly because of its resemblance to the small, brown, flightless bird. It has been used in China as the basis for flavorful wine and has a long tradition of use as a beverage. Kiwi juice has been used in some cultures as a traditional meat tenderizer. Other reported traditional uses include treatment of urinary calculi and use as a diuretic, febrifuge, and sedative.2, 3, 4
The main protein component of kiwi fruit is actinidin, a thiol-protease. It accounts for about 50% of the soluble protein content of the fruit and is also its major allergen. The gene for actinidin has been sequenced. The proteolytic activity of actinidin is similar, but not identical, to that of papain. A glycoprotein inhibitor specific for pectin methylesterase has been isolated from the fruit; it is ineffective against other polysaccharide-degrading enzymes, such as polygalacturonase and amylase.5, 6, 7, 8, 9, 10
The aroma profile and the aroma-active components of kiwi fruit have been extensively investigated.8 More than 80 compounds have been identified in the volatile fraction of kiwi fruit; about 35 components appear to contribute to the aroma of kiwi fruit puree. The composition of the volatile fraction changes rapidly as the fruit matures from fresh, mature, to overripe, with a decrease in C6 compounds such as hexanal, hexenol, and ethyl butyrate, and an increase in terpene esters. The major compounds isolated from fresh puree include 3-methyl-2-butanone, 3-hydroxy-2-butanone, (E)-2-hexenal, ethyl 3-hydroxybutyrate, phenylethyl alcohol, alpha-terpineol, and geraniol. None of the flavor compounds are unique to kiwi fruit.11, 12
Several antimicrobial compounds have been isolated from kiwi fruit. Seven phytoalexins were isolated from a methanol extract of the unripe fruit previously wounded and inoculated with fungus. The isolated antimicrobial agents included a novel triterpene phytoalexin named actinidic acid, as well as arjunolic acid, asiatic acid, and 23-hydroxytormentic acid. A single-chain, antifungal, thaumatin-like protein, thought to be the only defense protein present in kiwi fruit, also has been identified. Kiwi fruit has high concentrations of ascorbic acid, carotenoids, folate, potassium, magnesium, and copper.4, 13, 14 Isoflavones and vitamin E are also present.4, 15
Uses and Pharmacology
A thaumatin-like antifungal protein isolated from kiwi fruit showed modest activity against Botrytis cinerea and weaker inhibitory activity against Mycosphaerella arachidicola, Coprinus comatus, and Physalospora piricola.14
Kiwi fruit was found to have the highest concentration of ascorbic acid of a group of commonly eaten fruits and vegetables in an in vitro investigation of the antioxidant power.27 One kiwi fruit contains about 100 mg vitamin C, or equivalent to the recommended US daily intake. A study comparing the carotenoid content of a variety of food showed a higher proportion of lutein plus zeaxanthin (the major carotenoids in the human eye) in kiwi fruit than in spinach (54 and 47 mole%, respectively).28 In vitro and in vivo studies have been conducted to demonstrate the antioxidant activity of kiwi fruit.29, 30 In contrast to animal studies, human steady-state and pharmacokinetic bioavailability studies found no difference in bioavailability between vitamin C from a synthetic chewable tablet or eating skinless kiwi fruit.44, 45
The plant roots are used in traditional Chinese medicine and contain tripenoids with demonstrated weak inhibitory effects in vitro against the growth of several human cancer cell lines.17
Studies have been conducted in hypercholesterolemic mice fed preparations containing kiwi fruit and hawthorn, with positive results.18
Among healthy volunteers, platelet aggregation and plasma triglyceride levels were reduced after 28 days of fruit consumption. No effects on high-density lipoprotein or low-density lipoprotein cholesterol were observed.19, 20
There are no animal data supporting the use of kiwi fruit for improved GI function. Mice with inflammatory bowel disease fed kiwi fruit have been studied; however, effects on GI function were not reported.21
The fiber content of kiwi fruit is suggested to be about 3.5 g per 100 g of fruit.4, 22 A small, unblind clinical trial evaluated the effect of kiwi fruit on colon transit time and defecation frequency in healthy adults and in those with irritable bowel syndrome. Improved bowel function with kiwi fruit consumption compared with placebo was observed.23 Further small studies support anecdotal reports of laxative effects of kiwi fruit.22, 24
Limited preliminary clinical studies suggest consumption of kiwi fruit may assist in upregulating the immune system.20 A small study of elderly patients found kiwi fruit consumption reduced the severity and duration of symptoms associated with upper respiratory tract infections. Indicators of immune function (natural killer cell activity and phagocytosis) did not differ from those of the comparator banana group.26
Clinical trials are lacking to inform therapeutic dosing.
One kiwi fruit contains about 100 mg vitamin C (approximately the recommended US daily intake) and considerable quantities of the carotenoids lutein and xanthine.27 In humans, bioavailability of vitamin C from consuming skinless kiwi fruit was found to be equal to that of a synthetic chewable vitamin C tablet.44, 45
Pregnancy / Lactation
GRAS when used as food. Safety and efficacy for dosages higher than those found in foods is unproven and should be avoided.
None well documented.
The serotonin concentration of the fruit is approximately twice that of tomatoes and one-third that of bananas. Therefore, ingestion of kiwi fruit can increase urinary excretion of 5-hydroxyindoleacetic acid and may interfere with laboratory analyses for this serotonin by-product.31
Allergy to kiwi fruit and the vine is well documented in the literature, and includes oral allergy syndrome, contact dermatitis, Kounis coronary syndrome, and anaphylaxis. Trace amounts of kiwi fruit have been responsible for some of these reactions.32, 33, 34, 35, 36, 37, 46 Although acute pancreatitis in the course of an allergic reaction to a food substance is rare, a case report describes a patient with repeated attacks of acute pancreatitis secondary to kiwi fruit ingestion.38
Cross-reactivity of kiwi fruit with several other allergens, including birch and meadow fescue grass pollens, latex, avocado, and banana has been reported.39, 40, 41, 42 The major allergen appears to be the proteolytic enzyme, actinidin. Industrial heating and homogenizing techniques appear to diminish the likelihood of allergic reactions.43
Consumption of relatively large quantities of kiwi fruit may result in diarrhea.20
Information is lacking.
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