The kiwi is an egg-shaped fruit that grows on a vine (Actinidia chinensis). It has a thick, brown, and hairy skin which, despite its uninviting appearance, is edible. It contains a green, rather firm and very juicy flesh with hundreds of tiny black seeds. Kiwi is native to China, it was called then “Chinese gooseberry” but at the beginning of the twentieth century, it was renamed “kiwi” because of its hairy skin reminding those of the apteryx (called kiwi). This bird is endemic to New Zealand, a country in which this fruit was developed and improved. Formerly an exotic fruit, the kiwi is now cultivated everywhere where the climate is warm, especially in southern Europe.
The story of the kiwi
The kiwi belongs to the genus Actinidia including about 50 species, all native to the mountainous regions of China. In their natural habitat, plants climb along the trunk of the trees. They sometimes cover them entirely. In China, people harvested the fruit since more than a thousand years. Meanwhile, in the United States and Europe the fruit remained unknown until the middle of the 19th century. Then, travelers brought the seeds and established a few specimens in botanic gardens where you can appreciate them for the beauty of their foliage.
However, it’s only in the middle of the 20th century when kiwis were cultivated on a large scale. There were first cultivated in New Zealand, where people selected large fruit varieties. Then, the same thing happened in California. The fruit has appeared on the shelves of our markets in the 1980s, in the wake of the new cuisine coming from California.
Today, the kiwi is grown in many parts of the world. The main producers being the United States New Zealand, Australia, Chile, Japan, Italy, Greece and France. You can find it all year long because it is produced in the North and the South hemispheres and it lasts a long time after harvest.
The fruit is sold fresh. Kiwi can be found in marinades, jelly, jams, ice cream, chutneys, wine and dry. Because of its richness in actinidin, an enzyme related to papain, it is sometimes used to tenderize the meat. In addition, its fibers contained in its leaves and trunks are used to make strings and paper.
Health profile of kiwi
A single kiwi contains an impressive amount of fiber. This fruit has a lot of antioxidants. So, consuming it regularly could prevent the appearance of cardiovascular disease and certain cancers.
The benefits of kiwi
Cancer. Possible cases of the development of some cancers can come from oxidative damage to DNA. During a study, researchers have observed a decrease in the oxidation of DNA and an increase in the antioxidant capacity of blood among subjects who consumed 1 kiwi per day during 3 weeks. Researchers also found that the cell’s DNA among people who consumed 500 ml (2 cups) of kiwi juice was more resistant to oxidation and also to damages which can occur. This study showed the extract of kiwi proved to be more effective than vitamin C (recognized for its antioxidant power) in the protection against oxidative damage to DNA. This suggests that antioxidant power of the kiwi would not only be due to its vitamin C content.
Cardiovascular disease. A study among humans demonstrated that the kiwi could lead to a reduction of the risk of heart disease. Researchers found that consumption of 2 or 3 kiwis per day during about 1 month brought a decrease in platelet aggregation and a decrease in blood triglycerides, 2 risk factors associated with cardiovascular disease. Regular consumption of kiwi among people with high lipid levels, could also contribute to improve the lipid profile (good and bad cholesterol ratio) and increase the amount of vitamin C and E in blood levels.
Constipation. Kiwi may be effective for patients with constipation disorders, thanks to its high content in dietary fiber.
Healing. A study among rats showed that kiwi would help the healing of wounds better than applying a traditional antimicrobial cream. Thanks to its antibacterial properties as well as its ability to modulate angiogenesis. Kiwi could also be effective in the treatment of chronic ulcers at a lower cost.
More studies will be needed to confirm the various beneficial effects on health due to the kiwi before recommending consumption of this fruit in the prevention or treatment of diseases in particular. However, several forward-looking and epidemiological studies support that a high intake of vegetables and fruits helps maintaining a good health by reducing the risk of cardiovascular disease, certain cancers and chronic diseases.
What is the kiwi?
The kiwi contains many phenolic compounds, including phenolic acids, (epicatechin, catechin), procyanidins and flavonols (quercetin, kaempferol). These compounds, found in plants, have antioxidant properties. They can help prevent the appearance of several diseases, including some cancers, cardiovascular disease and various chronic diseases by neutralizing free radicals in the body.
Two kiwis provide more than 5 g of fiber, approximately 15% of the recommended daily intake. A diet rich in fiber can prevent constipation and contribute to the prevention of cardiovascular disease, type 2 diabetes and appetite control.
Kiwi is a food possibly causing oral allergy syndrome. This syndrome is an allergic reaction to certain proteins of various vegetables fruits and nuts. It affects people with allergies to pollen and is almost always preceded by hay fever. Thus, when some people allergic to ragweed consume raw kiwi (cooking breaks down usually proteins allergens), an immunological reaction can occur. These people suffer from itching and burning in the mouth, lips and throat. The symptoms may appear and then disappear, usually a few minutes after the person has consumed or touched the food. In the absence of other symptoms, this reaction is not severe and consumption of kiwi doesn’t have to be avoided in a systematic way. However, it is recommended to consult an allergist to determine the cause of the reactions among plant foods. The latter will be able to assess whether special precautions should be taken.
Allergy to kiwi seems to be more frequent and is often associated with other allergies. Indeed, several cases linked with latex and pollen allergies have been reported during the past years. People allergic to pollen or latex can demonstrate a hypersensitivity to the kiwi (as well as banana and avocado), and inversely. A protein contained in the kiwi named the actinidin, is recognized as an allergen. However, other proteins may also be involved. Reactions may vary from urticaria to anaphylactic reactions. Some factors that influence the digestion process of proteins (such as the pH of the stomach) as well as the environment in which individuals live could explain the differences in reactions between two people with kiwi allergies. Given the potential severity of the reactions, people allergic to latex or pollen should be particularly vigilant. It is recommended to consult an allergist to determine the cause of the reactions to certain foods and the precautions to be taken.
Selection and conservation
The kiwifruit must be intact, firm and without spots. Ideally, the flesh should give slightly under pressure, the fruit offered in supermarkets are usually firmer but they are harvested before full maturity. Leave those that are soft or damaged. The size of the fruit has no impact on its quality. In large grocery stores there is a new variety of yellow flesh kiwi.
Refrigerator. The firm fruit will keep several weeks in the refrigerator or a few weeks at room temperature.
Freezer. Cut the kiwis in slices and put them in the freezer on a metal plate. Then put them in an airtight container. You can also make a puree and freeze it.
Ecology and environment
The majority of kiwis from trade are not any of the 50 listed plant species, but of a single selected variety only. This is a unique situation in agriculture. Most of the kiwi plants cultivated in New Zealand would come exclusively from two female plants and a male plant, which came from China at the beginning of the 20th century. The gene pool of cultivated kiwis could be dangerously narrow.
For the time being, this plant which made its entry only recently in the big cultures, stayed free from insects and diseases. However, there is a concern about this situation that can quickly change. In just 100 years, global demand has passed, from practically zero to 1 million tons. To meet this growing demand, the cultures are now produced on large areas. Therefore, it becomes urgent that new varieties are selected and other species are involved to avoid a similar epidemic as the one in Europe, particularly Ireland, has experienced with the potato in the 19th century.