In the latest issue of The Lancet-Gastroenterology and Hepatology, the article in the Diet section shares an interesting topic: Does kiwi have a health effect? The authors, from King’s College London’s Department of Nutritional Sciences and the School of Medicine at Deakin University in Australia, explore potential mechanisms and related clinical trials around intestinal and extraintestinal health.
Screenshot source: The Lancet Gastroenterology and Hepatology
The authors point out that kiwis are nutritionally good, both green and yellow, and are generally rich in fiber, vitamin C and vitamin E, folic acid, and some bioactive compounds. One peeled kiwi contains about 1.5 g of fiber and 100 mg of vitamin C, 2-3 times the content of regular oranges. Moreover, kiwis are also rich in soluble fibers such as pectin and insoluble sources (cellulose and hemicellulose).
Effects on the gastrointestinal tract
Some studies have observed that green kiwis can increase the moisture content of the small intestine and ascending colon, increasing colon volume, softening feces and promoting intestinal peristalsis.
Kiwimaykiwi may also play a role in probiotics (food for probiotics). Tests showed that after 4 weeks of taking kiwi powder supplements, the abundance of Pteacudum prausnitzii in patients with constipation increased significantly, which produces butyric acid and has anti-inflammatory properties, so its increased abundance may be an important additional mechanism of kiwi’s effecton on the intestines.
Some trials that assess adult constipation therapy have therefore used the consumption of kiwi as an intervention. A few clinical trials showed an improvement in the number of defecations, processes and fecal traits in constipation patients after 2-3 kiwis a day. However, we need to carefully understand these results. The authors note that most of these trials are small and may not have appropriate placebo controls (a common challenge in dietary intervention studies), so the results of statistical analysis may not be entirely reliable.
Fortunately, some higher-quality studies are already under way. A randomized trial led by the University of Michigan’s digestive team (NCT03569527) is comparing the effects of kiwi, plum and dietary fiber supplements among constipation populations.
In addition, a protein hydrolysis called actinidin in kiwi has also attracted the attention of researchers. Model studies have shown that actinin helps to improve protein digestion in food compared to gastric protease-only participation. This has a potential application in food science – improving the tenderness of meat by changing its microstructure. In addition, some over-the-counter drugs have added this ingredient to improve people’s digestive function, although the authors say their clinical effects are inconclusive.
Potential physiological effects outside the gastrointestinal tract
There is also evidence that the addition of kiwi has a heart-protective effect, and in clinical trials, kiwi ingredients inhibit platelet coagulation, lower blood lipid levels and lower blood pressure. High levels of antioxidant sage in kiwis may also prevent endogenous oxidative damage. Limited supplementary evidence suggests that the ingredients in kiwi may help reduce the severity and duration of upper respiratory tract infections.
In addition, a trial in New Zealand is assessing the effects of kiwi on mood and fatigue (ACTRN1261700103358).
Is kiwi the new “super fruit”?
Although “super fruit” was originally a marketing concept, it has not stopped the growing number of fruits from being labeled in recent years. So, is kiwi really that good?
Overall, emerging evidence supports its potential benefits for gastrointestinal and heart metabolic health, the two experts said. But the scientific evidence for kiwis is still relatively weak compared to fruits with a stronger base for health research, such as apples, and the evidence for high-quality research is still accumulated.
Considering that kiwi is indeed nutritious and easy to buy, with personal preferences to eat 2-3 kiwis a day is no harm, there will be no adverse effects. In particular, because of its low fermentable carbohydrate content, it is unlikely to cause bloating and abdominal discomfort, and kiwi is a good choice for people with gastrointestinal discomfort or dysfunction. As for whether to choose green or yellow varieties, there is no study of which is better.