The nutritional and therapeutic benefits of kiwifruit

While more research needs to be conducted on humans, kiwifruit is looking particularly promising as a powerful medicinal food. Eating two of these delicious fruit per day is showing positive health benefits for many of the conditions that affect us today.

Kiwifruit (Actinidia deliciosa, also called Chinese gooseberry) is native to central and eastern China. The first description was recorded during the Song dynasty in the 12th century; however, it was gathered from the wild, not cultivated, and used as a medicine. During the 20th century the cultivation of the fruit spread from China to New Zealand as the first commercial plantings, although by 2018 China still produced half of the world’s crop.

There are about 60 varieties of kiwifruit, the most common being Actinidia deliciosa (fuzzy kiwifruit), but there is also golden kiwifruit (Actinidia chinensis), hearty red kiwifruit, purple kiwifruit and kiwiberries among others.

The fruit grows in temperate climates and is generally either male or female — both are needed for pollination, with one male to between three and eight females being a good ratio. Even self-pollinating kiwifruit are more productive with a male vine nearby, but all can be difficult to pollinate as the blooming times must be synchronised. The flowers are pollinated by birds and bees, but as they are notoriously difficult to pollinate, commercial growers often blow collected pollen over the female flowers.

Nutrition

One hundred grams of this delicious fruit provides 250 calories, 15 per cent carbohydrates with negligible proteins and fats. They are high in vitamin C particularly as well as vitamin K. They also contain some B vitamins, folate and dietary fibre as polysaccharides. Golden kiwifruit has similar nutrients but higher vitamin C and less fibre. Each fruit also contain minerals including potassium, alpha-linolenic acid (an omega-3 fatty acid) and carotenoids such as beta-carotene, lutein and zeaxanthin. Kiwifruit also contain a previously unknown type of vitamin E — ɣ-tocomoenol — with significant antioxidant activity.

Raw kiwifruit contain powerful protein-digesting enzymes such as actinidin, which will liquify gelatin based desserts and digest milk proteins, as well as the antioxidant and anti-inflammatory polyphenols as flavonoids.

Therapeutic uses of kiwifruit

Regular consumption of kiwifruit, along with a balanced diet, has been shown to have beneficial effects on immune function, including antioxidant and inflammatory activity. They have significant benefits in improving constipation and protein digestion, as well as in preventing respiratory infections. Improvement in brain function and mood regulation have also been researched.

Antioxidant
With its antioxidant properties, kiwifruit has been shown to protect cellular DNA against oxidative damage both as a large single dose of the fruit as well as with longer-term consumption. This ability to protect against DNA damage and in modulating DNA repair has relevance to the reduction of cancer risk.

Gastrointestinal system
The actinidin component (a proteolytic enzyme unique to kiwifruit) has shown protein-digesting activity in both the stomach and the small intestine and generally promotes gut health. Kiwifruit have been shown to reduce constipation and abdominal discomfort and relieve other gastrointestinal disorders such as irritable bowel syndrome. The fruit triggers favourable changes in the human colonic microbiome as it functions as a prebiotic due to high polysaccharides and encourages the growth of lactobacilli and bifidobacteria.

By improving protein digestion and with the high vitamin C levels, kiwifruit improves iron absorption (and therefore iron levels) in those with anaemia.

Kiwifruit has also shown anti-obesity effects by improving digestion as well as reducing adipocyte (or fat cell) size and activity, along with its role in insulin management, including glucose management and being low-GI, and in reducing insulin resistance and inflammation. While the anti-obesity research has been largely conducted on animals it holds promise for human research.

Respiratory system
Regular consumption of kiwifruit has been shown to have antimicrobial properties, both in preventing upper respiratory infection and improving symptoms of these infections, particularly in otherwise healthy older adults. This effect is partially through increasing plasma levels of vitamin C, a known immune stimulant.

Neuroprotective qualities
The high levels of antioxidants in kiwifruit along with significant anticholinesterase activity and anti-inflammatory activity generate neuroprotective effects, reducing the risk of stroke and dementia and protecting against spinal neuron degeneration.

In an interesting study on young adult males with mood disturbances where the participants ate half to two kiwifruit per day for six weeks, the higher dose of two fruit per day significantly improved their mood, reducing both depression and fatigue.

Cardiovascular system
An interesting study was done on 43 people in Taiwan with high cholesterol, which found that after eating two kiwifruit per day for eight weeks their HDL concentration (the “good” cholesterol) was significantly increased and their LDL levels correspondingly decreased, along with reduction of oxidation of the LDLs, reducing the risk of atherosclerosis. Vitamin C and E levels also increased significantly over this time.

Another study showed cardioprotective effects by lowering platelet stickiness, plasma lipids and blood pressure in humans when two or three fruits were eaten daily for 28 days. The consumption of kiwifruit also lowered blood triglycerides by 15 per cent. The blood pressure lowering activity of kiwifruit was attributed to the flavonoid component which in in vitro studies showed inhibition of ACE activity.

Caution

The actinidin in kiwifruit can be a common allergen and in some individuals it causes itching and mouth pain and wheezing. Occasional anaphylaxis can also occur.