The secrets of kiwifruit

Kiwi is the fruit that is often called the “Vitamin Bomb” in Bulgaria. With its rich content of vitamins and minerals, antioxidants and fiber, it is good to include it more often in our daily healthy menu. In order to make the most of the Vitamin C content, it is recommended to consume kiwi fruit raw.

An early Chinese pharmacopoeia dating from the Tang Dynasty (AD 618-907) lists a whole range of drugs with mihoutao, the Chinese name commonly used for actinidia (kiwifruit) species. Among the therapeutic effects, the most frequently mentioned are: digestion support, reduction of discomfort and pain in the upper abdomen, elimination of vomiting, reduction of the level of irritability. Traditional Chinese medicine in ancient times found that “Chinese gooseberry”/ kiwi fruit/ has cold properties that are beneficial for the spleen, liver, stomach. Today, it is also believed that kiwi balances the stomach and spleen, soothes the liver, thus improving the work of the digestive system. In the early stages of stomach cancer or after surgery and chemotherapy, eating two or three kiwis can help reduce nausea and improve digestion/ there is research and evidence/. According to traditional Chinese medicine, kiwifruit helps the body fight cancer cells and is suitable as a daily food for people with predominant “heat” suffering from stomach cancer. However, with an excess of “cold” in the body, kiwi in the diet should be limited, otherwise overeating can provoke diarrhea.

Plant

Kiwifruit is a vigorous, woody, dioecious vine with a large, whitish to brown, lamellated core. It has striated brownish stems and young branches. Its leaves are alternate which are subobicular or obovate orbicular in size about 6-17 × 7-15 cm. The unisexual flowers are orange-yellow on brown hairy pedicels. There are usually five sepals and petals. The sepals are broadly ovate to oblong-ovate in shape. The petals are broadly obovate, have a base with short claws and a rounded tip. The ovoid fruit measures 5 to 6 cm and is densely spiky when ripe. The fruits have firm, juicy flesh that is bright green in color and has a sweet to sour taste. The center of the fruit contains various small purple to black seeds.

Actinidia can survive for more than 50 years and bear fruit.

Leaves

The leaves are alternate, deciduous and long-stalked. They are oval to almost round with a heart-shaped base and 7.5-12.5 cm long. While young they are laminated with red hairs, and when mature they are dark green and hairless on their upper surface. The lower surface of the leaves has prominent and light colored veins.

Flowers

The fragrant flowers are unisexual or dioecious, located singly in the axils of the leaves. It has five to six petals. Initially they are white in color which change to light yellow. The flowers are 2.5-5 cm wide.

Fruits

The oblong fruits are 6.25 cm long. The fruits have a reddish-brown skin that is covered with stiff, short, brown hairs. It has firm flesh that is juicy and shiny. The flesh is bright green or yellow in color. It has a slightly sour to quite sour taste that resembles strawberry or gooseberry.

The fruits of Actinidia deliciosa /commonly known as green kiwifruit/ have a brown skin outside and green flesh inside, it is the most commonly cultivated plant with many varieties and different fruit shapes.
The fruits of Actinidia chinensis /commonly known as golden or yellow kiwifruit/ have a smooth brown skin on the outside, with yellow flesh inside and small black seeds. The coating is thin and does not need to be peeled.
The fruit of Actinidia arguta /often sold under the name kiwiberry or cocktail kiwi/ is actually a small kiwi about the size of a grape. Compared to the “normal” kiwi, a kiwiberry includes a thin, hairless skin, and the fruit can be eaten whole, just like a berry or perhaps a grape. In terms of nutritional value as well as taste, sweet kiwi is just like regular kiwi.

Composition of kiwi fruit

Both green and yellow kiwis are extremely rich in vitamins C, E, K, folate, carotenoids, potassium, copper, fiber and phytochemicals, which scientific research shows work synergistically. Antioxidants in kiwi fruit include: lutein, zeaxanthin and β-carotene, chlorophyll, quinic acid, glucosyl derivatives of caffeic acid, β-sitosterol, chlorogenic acid, phenols, including flavones and flavonoids.

Vitamin C. The level of ascorbic acid in green kiwifruit typically ranges from 70 to 120 mg per 100 g wet weight. The high content of this vitamin and low tannin content in kiwifruit is thought to explain why sliced fruit does not develop the typical browning reaction seen in most other fruits. In yellow kiwi fruit, the Vitamin C content is about 160 mg per 100 g wet weight.
Vitamin E. Both yellow and green kiwi contain relatively high levels of vitamin E compared to other fruits – 1.3-1.40 and 1.3-1.46 mg per 100 g, respectively. Mainly in the form of α -tocopherol present in the pulp. A group of Italian researchers proved that α-tocopherol is associated with the cell membranes of the pulp and is bioavailable in kiwi fruit. This is indirectly confirmed by the increase in the concentration of vitamin E in the blood plasma after consumption of green and gold kiwi. The same researchers identified a new form of vitamin E in kiwi fruit, δ-tocomonoenol, noting that its ability to scavenge radicals also significantly affects overall antioxidant activity.
Folic acid. Kiwifruit is often cited as a good source of folic acid. Since folic acid /Vitamin B9/ is easily destroyed by cooking, its presence in green leafy vegetables, which are usually processed, is less valuable than in kiwifruit, which is more often consumed raw. Thus, fresh kiwi fruit can make a healthy contribution to the overall diet, especially during pregnancy when meeting folic acid needs becomes more difficult.
Dietary fiber. Dietary fiber analysis of fruits shows that they contain about one-third of soluble and two-thirds of insoluble fiber. At the same time, the “golden” kiwi contains significantly less fiber than the green one. The dietary fiber in kiwifruit comes almost entirely from the plant cell walls (more precisely from the polysaccharides that form the main structural components of the walls). When choosing kiwi as a dietary product, it should be borne in mind that during the ripening of the fruit, the concentration of starch rapidly decreases and the content of fructose and glucose increases, which among the sugars prevail in kiwi – in some varieties in a ratio of 1: 1 .A small amount of sucrose appears when the fruit is ripe and ready to eat. At the same time, it is interesting that the glycemic index of kiwi is relatively low: green varieties – 39.3 ± 4.8, “golden” – 48.5 ± 3.1. A low glycemic response to kiwifruit has been observed in both healthy individuals and those with type 2 diabetes.

Beneficial properties

Kiwifruit, which is part of a healthy diet, can increase the level of “good” cholesterol (high-density lipoprotein) and lower triglyceride levels, suppress platelet aggregation and lower blood pressure. Eating golden kiwifruit with iron-rich foods boosts low iron levels, while green kiwifruit promotes digestion and relaxation. As a rich source of antioxidants, kiwi fruit can protect the body from endogenous oxidative damage. The effects of kiwi fruit on metabolic markers of cardiovascular disease and diabetes are also being investigated, including studies on glucose and insulin balance, body weight maintenance, and energy homeostasis.

Digestion. Of particular interest are kiwifruits for promoting normal digestion in both healthy individuals and those with constipation and/or gastrointestinal disorders, including irritable bowel syndrome. The mechanisms of action underlying the change in stool consistency, reduction in stool transit time, and reduction in abdominal discomfort are related to: the water-holding capacity of kiwifruit fiber, beneficial changes in the colonic microbial community, and the main human metabolites and the presence of the proteolytic enzyme actinidin, unique to kiwi fruit, which promotes protein digestion in both the stomach and small intestine. In other words, there are several plausible mechanisms that may work both together and separately. The most important physical and chemical properties of kiwifruit fiber include hydration properties, which include: water retention, capacity and swelling, viscosity and properties that depend on the size, shape and porosity of the non-degraded particles. Scientific research shows that the swelling and water retention in kiwifruit fiber is higher than, for example, dietary fiber from wheat bran, more than 6 times higher than that of apple fiber and one and a half times higher than that of psyllium (fibers obtained from psyllium husks). Kiwi fiber can be fermented and many of them have beneficial properties through the production of short-chain fatty acids. Kiwi fiber may also promote beneficial changes in the colon’s microbial community and their metabolites, which are associated with gut health. In addition, several unique enzymes have been found in kiwifruit, among which actinidin (or actinidain) is the most common. It is distinguished by its biologically active potential. In an in vitro (“in vitro”) model of small intestinal digestion, actinidine-containing kiwi fruit extract was particularly effective in improving the digestion of whey protein, zein, gluten, and gliadin. Studies have shown that actinidin aids protein digestion in the stomach and iliac region, which may be especially beneficial for people with impaired digestive function.
Immune system. Kiwi fruit can support immune function and reduce the frequency and severity of colds or flu-like illnesses in at-risk groups. A number of studies have shown that kiwi consumption has a strong effect on plasma and muscle levels of vitamin C. All of this is important because ascorbic acid is absolutely necessary for a number of biological functions. It promotes the formation of collagen for the normal function of blood vessels, bone and cartilage tissue, gums and teeth and skin. In addition, it ensures the metabolism, the functioning of the nervous system, helps to normalize the psychological state, reduces fatigue and exhaustion, supports the regeneration of a reduced form of vitamin E, the absorption of iron and supports the normal function of the immune system during and after intense physical exertion .
Metabolic health. A number of studies have investigated the effects of green and gold kiwifruit on metabolic markers such as glucose and insulin balance, weight maintenance, and energy homeostasis. Current research shows that the glycemic response of kiwifruit as a whole food is different from what would be expected from its individual components. Regular consumption of green and golden kiwifruit has a beneficial effect on several physiological biomarkers, especially in people with metabolic disorders related to diabetes, cardiovascular disease, stroke and dementia. In a number of human studies, positive changes in cardiovascular disease biomarkers have been attributed to the antioxidant compounds present in kiwi fruit.
Oncology. The effect of kiwi fruit on cancer is usually discussed with caution, separating direct and indirect anticancer effects. The direct ones are probably related to the reduction of oxidative DNA damage (which is due to exposure to ascorbic acid) and a cytotoxic effect on cancer cell lines. The indirect ones are most likely related to increased daily bowel movements and increased content of lactic acid bacteria in intestinal feces, which ultimately helps reduce the risk of malignancies, especially colorectal cancer. The results of human studies on the antioxidant efficacy of kiwifruit are conflicting due to differences in experimental protocols, kiwifruit variety used, study number and duration, and biomarkers used. However, taken together, the results of these published studies suggest that adding kiwifruit to food may still potentially have direct or indirect anti-cancer and anti-inflammatory effects.
Heart problems. A scientific study shows that consuming three kiwi fruits a day for about 28 days helps lower triglycerides by 15% and blood clotting by 18%. Daily intake of kiwi fruit prevents the build-up of plaque and deposits in the arterial walls, thus preventing cardiovascular problems. It has a high content of protective polyphenols along with vitamin E, vitamin C and potassium, which effectively support the health of the cardiovascular system. The study shows that kiwifruit has inhibitory effects that help lower blood triglycerides. It reduces the platelet aggression response or the chances of blood clotting. Fruits have a fibrinolytic effect on blood vessels, which prevents the possibility of atherosclerosis and thromboembolism.
Promotion of vision.Kiwifruit helps promote eye health because it is high in zeaxanthin and lutein, which are the natural chemicals present in the human eye. Lutein helps prevent macular degeneration and the development of cataracts and glaucoma by filtering harmful blue light. Zeaxanthin together with lutein contributes to eye health. The study showed that consuming three kiwi fruits reduced the risk of macular degeneration, which is associated with vision loss in older people, by 36%.
Slows down aging. Kiwi is rich in antioxidants that reduce the effects of aging in the body. Antioxidants help neutralize free radicals that damage cells and accelerate the degeneration process, leading to changes in skin elasticity, thickness and firmness. Oil extracted from kiwi seeds is used in anti-aging products. The combination of lycopene, vitamin E, C and other substances counteracts free radicals and prevents premature aging. Reduces the appearance of fine lines and wrinkles. It reduces the effects of ultraviolet radiation on the skin, and antioxidants help to rejuvenate the skin and prevent early degeneration.
Blood pressure control. Along with strengthening the immune system, it also helps control blood pressure. A study conducted in 2014 showed that the bioactive compounds found in three kiwis a day effectively reduced blood pressure. It reduces the chances of health problems caused by high blood pressure, such as heart attacks and strokes. Kiwifruit is high in potassium, which has a vital role in body cells that helps maintain the balance of body fluids as well as electrolytes. Normalizes heart rate and blood pressure by neutralizing sodium effects.
Respiratory health. Taking vitamin C is beneficial for people with respiratory diseases such as chronic cough or asthma. Eases airways and controls symptoms such as nasal congestion and wheezing. The study showed that people who consumed 5 to 7 servings of kiwi per week had a 44% reduction in wheezing compared to those who had one serving per week. Chronic cough and shortness of breath decreased by 25% and 32% respectively.
Promotes sleep. Studies have shown that kiwi fruit has many beneficial compounds such as serotonin and antioxidants that are helpful in treating sleep disorders. Consume two kiwi fruits just one hour before bedtime, which helps induce sleep. It has good serotonin content which promotes better sleep. Kiwi consumption promotes sleep onset and reduces wake time after onset and provides relief from sleep disturbances. Kiwi has flavonoids such as quercetin, narigenin, catechin, rutin, and epicatechin that regulate sleep-inducing receptors and is considered an effective plant-based sedative agent. Kiwi peel is an effective ingredient for developing natural sleep aids.
Prevention of cancer. In Chinese folk medicine, kiwi is used to treat various types of cancer such as breast cancer, liver cancer, lung cancer, and stomach cancer. Kiwifruit extracts inhibit the proliferation of cancer cells and prevent endogenous DNA damage. This fruit is effective against cancer because it is cytotoxic to malignant cancer cells without affecting healthy cells. Carotenoids, antioxidants, vitamins with fiber effectively protect against cancer. The phytochemical catechin found in kiwi reduces the toxicity of anticancer agents by promoting bone marrow proliferation.

Precautions

Some nutrients in kiwi can interact with medications or cause other adverse effects.

Beta blockers Doctors often prescribe these drugs for people with heart disease. Beta-blockers can cause blood potassium levels to rise, so people taking this type of medication should monitor their potassium intake.
Kidney problems Consuming too much potassium can also be harmful for people whose kidneys are not working properly. If the kidneys are unable to remove excess potassium from the blood, life-threatening complications can occur.
Blood thinners People at risk of heart disease may take blood thinners, such as warfarin (Coumadin). Kiwi contains a significant amount of vitamin K, which can interfere with the action of blood thinners. Anyone using these medications should consult a doctor before increasing their intake of foods that contain vitamin K.
Allergy Some people experience allergic reactions to kiwifruit. Anyone who develops hives, a rash or swelling after eating kiwi should seek medical attention. A severe reaction can lead to anaphylaxis, which can be life-threatening. The plant enzyme actinidain contained in kiwi fruit is related to the enzyme bromelain in pineapple and the enzyme papain in papaya, so people allergic to pineapple and papaya may also be allergic to kiwi fruit.