A study examining the effects of green kiwifruit on sleep quality and the sleep-wake cycle in healthy males has been awarded funding of $31,800 over 12 months by the High-Value Nutrition (HVN) Ko Ngā Kai Whai Painga National Science Challenge. Kiwifruit has been shown to improve digestive health and, more recently, psychological well-being[i].

This study builds on previous research, which showed that sleep quality is improved with the daily consumption of two Aotearoa New Zealand green kiwifruit for four weeks.

The study is being conducted by Riddet Institute-funded PhD candidate Alex Kanon, under the supervision of Dr Sharon Henare, Ngāti Whātua, Ngā Puhi, Senior Lecturer in the College of Health at Massey University, in collaboration with Zespri International Limited, who are providing contributions of fresh green kiwifruit. The team will investigate whether the consumption of fresh green kiwifruit (without skin) will improve sleep quality outcomes and increase the urinary concentration of metabolites central in the regulation of sleep-wake cycles. It will also investigate whether these effects will be enhanced using a freeze-dried form of kiwifruit that includes the skin of the fruit.

“There is some evidence from scientific studies that kiwifruit promotes sleep but how it does that we don’t really know,” says Dr Sharon Henare, Senior Lecturer, Massey University.

“We’re interested in identifying the mechanism by which kiwifruit may be acting to improve sleep and whether this involves an increase in the neurochemicals responsible for the regulation of sleep-wake cycles.  The potential to use a natural product such as having kiwifruit after dinner appeals as a simple solution to improve sleep, she says”.

Sleep is essential for the cellular repair of the body. One night of sleep disturbance can affect a person’s ability to concentrate which may increase technical errors and decrease overall mood the following day. In addition, sleep, or the lack of it, is increasingly recognised as a risk factor for obesity,[ii] type 2 diabetes[iii] and cardiovascular disease[iv].

Sleep promoting foods have been shown to increase the levels of the neurohormone melatonin and its precursor serotonin[v]. Both hormones play central roles in the regulation of sleep-wake cycles.

New Zealand grows top quality kiwifruit that has a nutrient-dense flesh and skin that is high in vitamin C, folate and fibre. Kiwifruit also contains 6ug/g of serotonin, which is considered high[vi].

The project is a multi-arm, randomised, controlled, trial that includes 24 men – 12 with poor sleep quality, and 12 with good sleep quality and will assess sleep quality in response to their evening meal supplemented with either fresh green kiwifruit (without the skins), whole freeze-dried green kiwifruit powder (including the skin), or water.

The project aims to determine the effect of green kiwifruit on objective and self-reported sleep quality and also the effects of green kiwifruit on self-reported psychological well-being.

“This study strongly aligns with HVN’s mission and strategy to develop high-value foods with validated health benefits to drive economic growth through research excellence,” says Joanne Todd, High-Value Nutrition Challenge Director.

“The anticipated outcomes may reveal the potential for the formulation of unique Aotearoa New Zealand kiwifruit-based products with health messaging related to sleep quality and mood, while also potentially bringing increased economic benefits for kiwifruit growers.”

The HVN Challenge is a mission-led programme of innovative research into the health attributes of New Zealand-produced foods for our major export markets.

The Challenge will, over the next three years, fund a number of projects through a competitive contestable funding process, and has recently approved other contestable funding opportunities with business partners.

[i] https://doi.org/10.3390/nu12092898
[ii] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2398753/
[iii] https://pubmed.ncbi.nlm.nih.gov/18246976/
[iv] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910533/
[v] https://www.mdpi.com/2072-6643/12/4/936/htm
[vi] https://pubmed.ncbi.nlm.nih.gov/29470689/