Kiwis, which are also known as kiwi fruit, are fuzzy brown or gold fruits that are actually berries. They are the fruit of a vine. Named by the New Zealand Marketing Board after the flightless bird of New Zealand with the same name. Kiwifruit packs an enormous nutritional punch in a relatively small piece of produce. While most people think of bananas as fruit with high levels of potassium, oranges as an excellent source of vitamin C. In reality, two kiwis have more potassium (SOS milligrams) than a banana and, twice as much vitamin C, (114 milligrams) as an orange. They also contain folate, magnesium, vitamins A and E, soluble and insoluble fiber, lutein, and copper.
“By one scientific measure, many professionals consider kiwi fruit the most nutrient-dense fruit”. Moreover, there have been a number of intriguing research studies on these berries.
The nutritional benefits of kiwi include adding antioxidants to the blood. Which neutralizes the assault of free radicals. A study that appeared in 2007, in the Journal of the American College of Nutrition, examined the effects of antioxidants in several fruits. Many fruits contain high amounts of antioxidants, which increased the number of antioxidants in the blood of volunteers eating these fruits regularly. Of the fruits that they tested, the best results were obtained from grapes, kiwi slices, and wild blueberries. The researchers note that the increase in the number of antioxidants in the blood directly associates with a decrease in the risk for chronic illness. They advised people to eat high-antioxidant foods with each meal.
Because kiwifruit is so rich in antioxidants and because it neutralizes free radicals, it may well play a role in cancer prevention. In a European study published in 2003 in Carcinogenesis, healthy, non-smoking volunteers, who did not take antioxidant supplements or medication, ate varying amounts of kiwis for three-week periods of time. The study times were followed by two week washout periods. Researchers measured the ability to repair DNA oxidation with an in vitro test; concentrations of dietary antioxidants were measured in blood plasma.
They found that the daily consumption of kiwis provides protection against DNA damage that may cause cancer. “The magnitude of these effects was generally not related to the number of kiwi fruits consumed per day. Kiwifruit provides dual protection against oxidative DNA damage, enhancing antioxidant levels and stimulating DNA repair. It is probable that together these effects would decrease the risk of mutagenic changes leading to cancer.”
Similar findings can be found in a 2006 study found in Nutrition Research. A small group of 12 healthy volunteers was used. Them, there were two groups of six each. One group consumed kiwis every day; the other group ate no kiwis. As in the previous study, researchers found that the volunteers who ate kiwis had a much greater ability to repair the DNA break age caused by free radicals. According to the researchers, eating a daily kiwi “may provide a sustainable population intervention that could reduce some of the risk factors associated with cancer.”
In a study, published in 2004 in Platelets Magazine, researchers from the University of Oslo in Norway focused their study on kiwi. Eating two or three kiwifruits each day had two effects. First, it thinned the blood along with reducing the risk of blood clots. Second, kiwi lowered the amount of circulating fat in the blood. In the study, subjects ate two to three kiwis a day for 28 days.
By the end of the study, the level of blood clotting was 18 percent lower. Similarly, the amount of plasma triglyceride (fat in the blood) saw a reduction of 15 percent. This effect was similar to taking a daily therapeutic aspirin. Without the side effects of inflammation and gastrointestinal problems are so often seen with the frequent use of aspirin. At the end of the study, the subjects were told to remove all kiwi fruit from their diets. Two weeks later, “their blood levels returned to pre-supplement period baseline levels.”
Another study, published in 2009 in the Journal of Food Sciences and Nutrition, investigated 43 subjects who had hyperlipidemia or high levels of blood fat. Everyone ate two kiwi fruits each day for eight weeks. “After eight weeks of consumption of kiwi fruit, the HDL-C concentration was significantly increased. Also, the LDL cholesterol/HDL-C ratio and total cholesterol/HDL-C ratio were significantly decreased. Vitamin C and vitamin E also increased significantly.” In other words, people dealing with high levels of blood fat obtain significant cardiovascular benefits from including kiwifruit in their diets.
In a study conducted at the University of Hong Kong and published in 2007 in the World Journal of Gastroenterology, researchers recruited 33 people who suffered from constipation as well as 20 healthy volunteers. For four weeks, everyone ate a kiwifruit twice daily. The researchers noted that there was improvement not only in the constipation symptoms, “but also in terms of colonic transit times and rectal sensation”. Moreover, none of the subjects reported problems with gas or bloating.
In a study from New Zealand published in 2002 in the Asia Pacific Journal of Clinical Nutrition, 38 people over the age of 60 consumed their normal diet with or without one kiwifruit for each 30 kg (each kg is equivalent to 2.2 pounds) of body weight. After three weeks, the subjects crossed over and consumed what they hadn’t consumed during the first part of the study. Daily records chronicled the frequency of defecation and characteristics of the stool. The researchers noted that “the regular use of kiwifruit appeared to lead to a bulkier and softer stool. As well as more frequent stool production.
While it is not a serious condition, benign prostatic hyperplasia (BPH), is an enlargement of the prostate gland. This condition only affects men. The condition often occurs as men age, and may be very uncomfortable and challenging to everyday life. Men may experience urinary frequency that often disrupts sleep. A 2007 article in Life Extension Magazine notes that members of the Life Extension Foundation have been reporting that eating a kiwi before bedtime has helped with their nighttime symptoms. Though there appears to be no research on the association between the nutritional benefits of kiwi consumption and symptoms of BPH. Men dealing with this medical problem may wish to try eating kiwi for several nights in a row.
A study published in 2007 in the Journal Of The Science Of Food And Agriculture examined organic and conventional kiwifruits grown on the same farm in California. Researchers found that this organic fruit contained higher levels of health-promoting factors. The nutritional benefits of kiwi when organic include higher levels of antioxidants and vitamin C.
In a 2004 article in Clinical & Experimental Allergy, researchers in Southampton, England, maintained that allergic reactions to kiwi fruit are fairly common. They note, “Kiwi fruit is a fruit that many consider being a significant food allergen. Capable of causing severe reactions, particularly in young children.” Yet, this is a poorly studied field. Many studies show that people who tend to be allergic are more likely to be allergic to kiwi.
Should kiwis be part of the diet? Unless someone has a known allergy, absolutely.
Like this post? Check out our post on the Nutritional Benefits of Cranberries too. We also cover similar research on the nutritional benefits of blueberries. Or, you could read an interview with a nutritionist about fruit and fitness.
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By Myrna Chandler Goldstein, Mark Allan Goldstein
