Editor’s Note: Each month, HerbalEGram highlights a conventional food and
briefly explores its history, traditional uses, nutritional profile, and modern
medicinal research. We also feature a nutritious recipe for an easy-to-prepare
dish with each article to encourage readers to experience the extensive
benefits of these whole foods. With this series, we hope our readers will gain
a new appreciation for the foods they see at the supermarket and frequently
include in their diets.
The basic materials for this series were compiled
by dietetic interns from Texas State University in San Marcos and the
University of Texas at Austin through the American Botanical Council’s (ABC’s)
Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Perez, ABC Special
Projects Director Gayle Engels, and ABC Chief Science Officer Stefan Gafner, PhD,
for their contributions to this project.
By Hannah
Baumana and Rachel Powersb
a HerbalGram Associate Editor
b ABC Dietetics
Intern (Texas State, 2017)
Overview
Kiwifruit
(Actinidia deliciosa, Actinidiaceae),
also known by the less common name “Chinese gooseberry,” is one of 50 known species
within the genus Actinidia.1
These species are climbing, woody vines with large, heart-shaped leaves and
cream-colored flowers that bloom in the spring. The flowers are dioecious, with
male and female blossoms found in separate individuals. The kiwifruit matures
in early winter and typically has brown fuzzy skin. Depending on the species,
the flesh is either green or yellow, but all species are filled with small
black, edible seeds.1 While A.
deliciosa accounts for about 90% of kiwifruit in international trade, two
other species are cultivated and sold commercially: A. chinensis and A. arguta.2
Actinidia deliciosa is the common
green kiwifruit.3 The most common cultivar of A. chinensis is “Hort16A,” known by the brand name ZESPRI, or “gold
kiwifruit.”4 Actinidia arguta
is referred to as “baby kiwi” or “grape kiwi” due to the small size of its
fruits.2 Actinidia species
are native to southwestern China, but they are now cultivated in New Zealand,
the United States, Italy, France, Chile, and Japan.5
Phytochemicals and Constituents
Kiwifruit
provides fiber, potassium, folate, phosphorus, copper, and vitamins A, C, E,
and K.3,6 In fact, one kiwifruit provides more than the Recommended
Dietary Allowance (RDA) of vitamin C for adults and almost 35% of the RDA of
vitamin K. Vitamin C has numerous health benefits, including anticarcinogenic and
immune-regulating properties.3,7 In addition, it plays a role in the
formation of collagen, a major component of connective tissue, skin, and bones.
Vitamin C intake also has been shown to help mitigate a number of conditions,
including cardiovascular disease and inflammation.8 Vitamin E is an
antioxidant that stops the oxidation of low-density lipoprotein (LDL)
cholesterol and protects cell membranes against damage caused by reactive
oxygen species.9 Vitamin E also helps maintain the structure and
function of skeletal, cardiac, and smooth muscles. Vitamin K regulates blood
clotting, aids in the transfer of calcium through the body, and supports bone
health, reducing the risk of osteoporosis and bone fractures due to age.10
Kiwifruit
is also a good source of fiber, which contributes to its laxative effect.
Additionally, the lignins in cellulose (a form of dietary fiber) are believed
to have antimutagenic properties due to their ability to increase the adsorption
of aromatic amines in the gut, thus preventing them from entering the blood
stream. Aromatic amines can act as carcinogens after they have been metabolized
by the liver.3
One
of the interesting compounds present in kiwifruit is actinidin, an enzyme that
helps to hydrolyze proteins. Due to the actinidin content of kiwifruit, other
fruits and dairy products will soften or curdle upon prolonged contact with the
chopped fruit, so kiwifruit should be added at the last minute to fruit salads
and other mixed preparations. Actinidin has been shown to improve digestion by
assisting with protein digestion and digestive motility.11 Kiwifruit
contains numerous other bioactive compounds, including organic acids, plant pigments,
and polyphenols. The primary organic acid in kiwi is citric acid, but it also
contains malic, quinic, gallic, and oxalic acids. Organic acids provide the
fruits with significant antioxidant properties.
Some
of the plant pigments present in kiwifruit include carotenoids and
chlorophylls, and some cultivars also contain anthocyanins.11 The
carotenoids include beta-carotene, lutein, violaxanthin, and 9’-cis-neoxanthin.3
When compared with other commonly consumed fruits, kiwifruit is the richest
source of lutein, which is a carotenoid that is highly concentrated in the
macula of the eye and is associated with lowering risk of cataracts. All Actinidia species contain chlorophylls a
and b, but levels are much lower in the gold kiwi variety. Some kiwifruits also
contain anthocyanins, but they are not a significant component of the
antioxidant capacity of the fruit. Glutathione is another important antioxidant
present in kiwifruit, and it not only prevents oxidative damage of cells but
also helps to keep vitamins C and E in their active form, regenerating their
antioxidant capacities.11
Historical and Commercial Uses
Kiwifruit
is featured in Chinese literature dating back to the 15th century.12
The kiwifruit was originally called mi hou
tao, or “monkey peach,” because monkeys would eat the fruit in the wild.4
Traditionally, both the root and the fruit of A. chinensis were used in traditional Chinese medicine and are known as xiao yang tao. The root of A. chinensis contains antiangiogenic
phytochemicals including triterpenes, polyphenols, and anthraquinones, and it
has been noted in the Chinese pharmacopeia as being useful for treating many
diseases, such as stomach, rectal, and breast cancers, as well as hepatitis
viral infections.12-14 The fruit of A. chinensis was used as a juice to quench thirst, aid digestion,
clear heat, and reduce irritability, inflammation, and vomiting.3,14
Other
Actinidia species were used for their
therapeutic effects as well. Historically, A.
macrosperma was used to stimulate the immune system and A. polygama was used as an
anti-inflammatory agent and to counteract allergies due to its anti-asthmatic
effect.3,15
Modern Research
Clinical
trials for kiwifruit primarily have focused on its effects on the digestive,
immune, and cardiovascular systems. Preliminary research has also investigated
the antioxidant properties of kiwifruit and its possible inhibitory effect on
cancerous cell growth.
Gastrointestinal System
Clinically,
kiwifruit has been shown to have a laxative effect. Daily consumption of the
fruit improved the frequency and ease of bowel movements and improved stool
bulk and softness in healthy older adults.3 In another study,
researchers found that daily kiwifruit intake relieved symptoms in subjects
suffering from chronic constipation, with no reports of adverse effects like
diarrhea.3 Additionally, a trial in healthy subjects who were not
experiencing constipation found no adverse gastrointestinal effects from daily
consumption of kiwifruit.16
These
gastrointestinal benefits are attributed to the lubricating effects of kiwifruit’s
pectin and the enzyme actinidin, which combine with the enzymes in the stomach
and the small intestine to improve digestion.4 The pectin and fiber present in kiwifruits also
function as prebiotics. Prebiotics help to modify the composition of the
bacterial flora in the gut so that healthy bacteria are stimulated and harmful
bacteria are suppressed. An in vitro study looked at the prebiotic effect of
the pectin present in kiwifruit compared to other prebiotics like inulin, guar
gum, and citrus pectin. The pectin in kiwifruit was more effective than these
prebiotics in reducing the intestinal adhesion of harmful bacteria and
increasing the adhesion of beneficial bacteria.17 In a mouse study on irritable bowel disease (IBD),
extracts of both green and golden kiwifruit were administered, resulting in a
potent anti-inflammatory effect. These results indicate that further research
should be done exploring the medicinal properties of kiwifruits in the
treatment of IBD.18
Antibacterial and Immunological Activity
In an
in vitro study, essential oil from A.
macrosperma produced inhibitory effects against a number of common
bacteria, including Escherichia coli
and Staphylococcus aureus, as well as
three common fungal species.3 In a mouse study, kiwifruit extract
was shown to alter innate and acquired immunity when the mice were injected
with cholera and diphtheria/tetanus vaccines.15 This could have
implications for improving immunity in vaccinated individuals, particularly
children and other high-risk populations.
Other
animal studies have shown that extracts of A.
arguta may have anti-allergenic effects, implying a potential for the use
of kiwi extracts as therapies for allergy conditions like bronchial asthma or eczema.3
A human trial observed the effects of daily intake of golden kiwifruit on both older
adults (older than 65 years) and young children (ages 2-5) in relation to cold
and flu-like illnesses. For the adults, those who ate four kiwifruits daily had
symptoms for fewer days over the course of a cold than the adults who ate two
bananas (Musa acuminata, Musaceae)
daily. In the preschool children, the odds of getting a cold or the flu
decreased by almost half in the children who ate two kiwifruits daily instead
of one banana.4
Cardiovascular System
There
is some evidence that kiwifruit may have the ability to affect risk factors for
cardiovascular disease, like blood pressure, plasma triglycerides, and platelet
aggregation. A human study showed that eating two to three kiwifruits per day
reduced triglyceride levels by 15% and reduced platelet aggregation response by
18% compared to control.19 Multiple studies have shown that daily
kiwi consumption improves not only triglyceride levels, but also the ratio of
total cholesterol to high-density lipoprotein (HDL) cholesterol. One clinical
trial studied male smokers who ate three kiwis per day for eight weeks. The patients
had significantly reduced blood pressure and angiotensin-converting enzyme
(ACE) activity (a component of the blood pressure-regulation process),
especially those with hypertension. A number of in vitro studies support the
claim that kiwifruit reduces platelet aggregation, but clinical trials are
conflicting and more human studies are needed to confirm this effect.4
Antioxidant and Cytotoxic Properties
The
vitamin and phytochemical composition of kiwifruit give it powerful antioxidant
properties. An in vivo study showed that kiwifruit juice ingestion increased
plasma antioxidant capacity within 30 minutes and that these levels were
sustained for up to 90 minutes. Though this was not a long-term study, this may
have implications for kiwifruit’s ability to fight oxidative stress.3
Similar findings were established through two human studies in the United
Kingdom, which showed that kiwifruit consumption improved antioxidant status of
both the plasma and lymphocytes of participants. One of these studies also
showed that kiwifruit seemed to stimulate DNA repair. A pilot study was
performed to extrapolate on this possibility and the results showed that kiwi aided
DNA repair for an average of 13 hours after ingestion.7
Though
vitamin C is known for its antioxidant power, it also has a synergistic effect
on iron absorption. In a study of young women with mild anemia (iron
deficiency), participants who consumed two golden kiwifruits with an
iron-fortified cereal daily had significantly improved iron levels compared to
participants who ate the cereal with a banana. The vitamin C content, along
with the carotenoids lutein and zeaxanthin present in kiwifruits, are likely
responsible for this outcome.4
There
is a great deal of investigation into the role of antioxidants and other
phytochemicals in the prevention of cancerous cell growth, but despite
kiwifruit’s history of use in traditional Chinese medicine, there are few
clinical trials establishing the connection of the fruit and its constituents
with cancer prevention or treatment. In vitro studies have shown that extracts of
Actinidia species may be toxic to
cancer cells. Additionally, mice studies have shown that kiwifruit juice
inhibits growth of sarcoma cells.12 Another
mouse study showed that catechin in the stems of A. arguta and the juice of A.
deliciosa increased bone marrow proliferation, which may have implications
for reducing the adverse effects of chemotherapy treatments. There has also
been evidence suggesting that the prebiotic effect of fiber found in foods may
change the bacteria in the colon, providing protection against colon cancer.3
Consumer Considerations
Though
it is poorly understood, there is an allergy risk associated with the fruits of
Actinidia species. Allergic reactions
can range from mild itching of the throat, mouth, and lips, and swelling to
anaphylaxis, though it is more common for reactions to be mild. The more severe
reactions typically occur in children.4 The prevalence of allergies
to Actinidia fruits may vary
geographically; in France, Finland, and Sweden, kiwifruit is one of the top ten
most common allergens.16 Allergies to kiwifruit are often
cross-reactive with other common allergens such as pollens, rye (Secale cereale, Poaceae), hazelnut (Corylus avellana, Betulaceae), chestnut
(Castanea spp., Fagaceae), banana,
and avocado (Persea americana,
Lauraceae). Heat treatment and industrial homogenization have been shown to
greatly reduce the allergic reactivity of green kiwi. These treatments are
often performed on processed products like beverages and jams.20
Kiwifruit
contains oxalate, which is from the salt of oxalic acid. Oxalates can cause
oral irritation in some individuals, and they can be risky for individuals with
a history of calcium oxalate-containing kidney stones. Oxalate in high
concentrations can also reduce the bioavailability of calcium, magnesium, and
iron in the body.3 Though kiwifruit contains more than 10 mg of
oxalate per serving (enough to be considered high levels), it would require
daily consumption of large quantities of kiwifruit for the levels of oxalates
in the body to become dangerous. Additionally, oxalate content decreases during
storage.16
Nutrient Profile21
Macronutrient Profile: (Per one fruit
[approx. 69 grams])
42 calories
0.8 g
protein
10.1
g carbohydrate
0.4 g
fat
Secondary Metabolites: (Per one fruit
[approx. 69 grams])
Excellent source of:
Vitamin
C: 64 mg (106.7% DV)
Vitamin
K: 27.8 mcg (34.8% DV)
Good source of:
Dietary
Fiber: 2.1 g (8.4% DV)
Potassium:
215 mg (6.1% DV)
Vitamin
E: 1 mg (5% DV)
Also provides:
Folate:
17 mcg (4.3% DV)
Manganese:
0.07 mg (3.5% DV)
Magnesium:
12 mg (3% DV)
Calcium:
23 mg (2.3% DV)
Phosphorus: 23 mg (2.3% DV)
Vitamin B6: 0.04 mg (2% DV)
Thiamin: 0.02 mg (1.3% DV)
Niacin: 0.24 mg (1.2% DV)
Riboflavin: 0.02 mg (1.2% DV)
Vitamin A: 60 IU (1.2% DV)
Iron: 0.2 mg (1.1% DV)
DV =
Daily Value as established by the US Food and Drug Administration, based on a
2,000-calorie diet.
Recipe: Kiwi,
Lemon, and Rosemary Shrub
Courtesy of Jerry
James Stone22
Ingredients:
- 1 1/2
pounds kiwifruit
- 2
slices of lemon
- 1 sprig
of rosemary
- 1 cup
sugar
- 1 cup
champagne vinegar
Directions:
- Peel
and thinly slice the kiwifruit. Arrange a layer of kiwifruit in a quart-sized
jar and sprinkle with sugar. Repeat the layering until all the sugar and fruit
is in the jar. Seal and let stand for five hours.
- Add
the lemon, rosemary, and vinegar to the jar. Seal and shake to combine and
dissolve the sugar, then let stand for 24 hours.
- Strain
the mixture through a sieve into a clean quart-sized jar. Seal and refrigerate.
To serve, mix two tablespoons of the shrub with sparkling water in an
ice-filled glass.
References
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Illustrated Guide to the World’s Food Plants. Washington, DC: The National
Geographic Society; 2008.
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A, Nowicka P, Oszmiański J, Golis T. Phytochemical compounds and biological
effects of Actinidia fruits. J Funct
Foods. 2017;30:194-202. doi:10.1016/j.jff.2017.01.018.
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DC, Skinner MA, Ferguson AR, Stevenson LM. Kiwifruit and health. In: Bioactive Foods in Promoting Health: Fruits
and Vegetables. Auckland, New Zealand; 2010:565-580.
doi:10.1016/B978-0-12-374628-3.00037-2.
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W, Gammon CS, Beck KL, Conlon C, von Hurst PR, Kruger R. Kiwifruit: our daily
prescription for health. Can J Physiol
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Wyk B-E. Food Plants of the World: An Illustrated Guide. Portland, OR: Timber
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Encyclopedia of Healing Foods. New York, NY: Atria Books; 2005.
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E, Ferguson LR, Cumin M, Thakur V, Karunasinghe N, Plank L. Kiwifruit
consumption reduces DNA fragility: a randomized controlled pilot study in
volunteers. Nutr Res.
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AC, Pullar JM, Moran S, Vissers MCM. Bioavailability of vitamin C from
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intakes. J Nutr Sci. 2012;1:e14.
doi:10.1017/jns.2012.15.
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A, Becker B. Facts about vitamin E. Weil website. August 2016. Available at: www.drweil.com/vitamins-supplements-herbs/vitamins/facts-about-vitamin-e/.
Accessed June 21, 2017.
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SD. Vitamin K. University of Maryland Medical Center website. July 16, 2013.
Available at: www.umm.edu/health/medical/altmed/supplement/vitamin-k.
Accessed June 22, 2017.
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L. Chapter three — The composition and nutritional value of kiwifruit. Adv Food Nutr Res. 2013;68:33-57.
doi:http://dx.doi.org/10.1016/B978-0-12-394294-4.00003-1.
- Motohashi
N, Shirataki Y, Kawase M, et al. Cancer prevention and therapy with kiwifruit
in Chinese folklore medicine: A study of kiwifruit extracts. J Ethnopharmacol. 2002;81(3):357-364.
doi:10.1016/S0378-8741(02)00125-3.
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WJ, Yu DH, Zhao M, et al. Antiangiogenic triterpenes isolated from Chinese
herbal medicine Actinidia chinensis
Planch. Anti-Cancer Agents Med Hist.
2013;13(2):195-198. doi:10.2174/187152013804711146.
- Hsu
HY. Oriental Materia Medica: A Concise
Guide. Long Beach, CA: Oriental Healing Arts Institute; 1986.
- Shu
Q, Mendis De Silva U, Chen S, et al. Kiwifruit extract enhances markers of
innate and acquired immunity in a murine model. Food Agric Immunol. 2008;19(2):149-161.
doi:10.1080/09540100802117198.
- Singletary
K. Kiwifruit. Nutr Today.
2012;47(3):133-147. doi:10.1097/NT.0b013e31825744bc.
- Parkar
SG, Redgate EL, Wibisono R, Luo X, Koh ETH, Schröder R. Gut health benefits of
kiwifruit pectins: Comparison with commercial functional polysaccharides. J Funct Foods. 2010;2(3):210-218.
doi:10.1016/j.jff.2010.04.009.
- Edmunds
SJ, Roy NC, Love DR, Laing WA. Kiwifruit extracts inhibit cytokine production
by lipopolysaccharide-activated macrophages, and intestinal epithelial cells
isolated from IL10 gene deficient mice. Cell
Immunol. 2011;270(1):70-79. doi:10.1016/j.cellimm.2011.04.004.
- Park
YS, Leontowicz H, Leontowicz M, et al. Comparison of the contents of bioactive
compounds and the level of antioxidant activity in different kiwifruit
cultivars. J Food Compos Anal.
2011;24(7):963-970. doi:10.1016/j.jfca.2010.08.010.
- Nishiyama
I. Fruits of the Actinidia genus. Adv Food Nutr Res. 2007;52(6):293-324.
doi:10.1016/S1043-4526(06)52006-6.
- Basic
Report: 09148, Kiwifruit, green, raw. United States Department of Agriculture
Agricultural Research Service website. May 2016. Available at:
https://ndb.nal.usda.gov/ndb/foods/show/2253. Accessed June 22, 2017.
- Stone
JJ. Kiwi, lemon & rosemary shrub (drinking vinegar). Jerry James Stone
website. December 4, 2013. Available at: jerryjamesstone.com/recipe/kiwi-lemon-rosemary-shrub-drinking-vinegar/.
Accessed June 22, 2017. [Editor’s note:
The linked webpage contains profanity.]
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