The nutritional intervention could serve as a ‘food-first’ approach to improving sleep quality not only in elite athletes but also in broader populations. 

Interview by Alyx Arnett

Could the simple addition of kiwifruit before bed improve sleep quality? This question forms the basis of a recent study that delves into the potential of the fuzzy fruit—a natural source of melatonin, serotonin, and antioxidants—to enhance sleep and recovery in high-performance athletes.

The study had elite athletes consume two medium-sized kiwifruits an hour before bedtime for four weeks.

Rónán Doherty, PhD, BA, MSc, RNutr, SENr, a lecturer and performance nutritionist at the Atlantic Technological University

“Due to the ‘food-first’ approach adopted by many athletes, there is scope for investigation of ‘functional food’-based interventions designed to promote athlete recovery and/or enhance sleep quality and quantity,” says lead author Rónán Doherty, PhD, BA, MSc, RNutr, SENr, a lecturer and performance nutritionist at the Atlantic Technological University. 

Previous research, though limited, has tied kiwifruit consumption to better sleep onset, duration, and efficiency in adults with self-reported sleep disturbances. Given that elite athletes often face sleep challenges such as habitual short sleep duration and poor sleep quality due to their demanding lifestyles, Doherty was interested in investigating the fruit’s potential benefits for this group.

The findings indicate that this nutritional approach holds promise not only for athletes but also for broader populations experiencing sleep issues.

[Editor’s Note: Read the study, “The impact of kiwifruit consumption on the sleep and recovery of elite athletes,” in Nutrients.]

What were your key findings?

From baseline to post-intervention, there were clinically significant improvements in sleep quality (improved Pittsburgh Sleep Quality Index global scores and sleep quality component scores) and improvements in recovery stress balance (reduced general stress and sports stress scales). Moreover, the intervention—consumption of two kiwifruit one hour before bed—improved sleep as evidenced by significant increases in total sleep time and sleep efficiency percentage and significant reductions in the number of awakenings and wake after sleep onset.

How does this study add to evidence that kiwifruit may improve sleep?

Potential nutritional interventions that could positively impact athletes’ sleep, causing resultant improvements in recovery, warrant investigation. The potential of nutrition to influence sleep is related to various neurotransmitters associated with the sleep-wake cycle (eg, melatonin and serotonin in kiwifruit). 

Although the research in this field is in its infancy, the current study adds to the limited body of evidence that kiwifruit consumption can positively impact sleep. The manipulation of the timing and dose of kiwifruit may have applications in terms of sleep and recovery (eg, antioxidant consumption in relation to training) in athletes that warrant further investigation.

What are the implications for the broader population?

Previous research has highlighted the potential for kiwifruit to improve sleep in other populations, such as hospital-based populations and students. Consuming two kiwifruit one hour before bed is a practical whole food-based intervention that can easily be implemented in real-world settings in various populations.

How might your findings influence dietary strategies for better sleep quality?

Kiwifruit is available in whole food form but is also consumed in various processed forms, such as drinks, sweets, lyophilized products, dehydrated products, and juices. Further research is warranted to develop kiwifruit products and/or protocols designed specifically to promote sleep and/or recovery in elite athletes.

For individuals considering melatonin supplements to improve their sleep, could incorporating kiwifruit into their diet be a viable and more natural alternative?

Kiwifruit has been shown to contain melatonin, which plays an important role in circadian rhythm regulation. Getting to sleep and maintaining sleep are easiest at and after the onset of melatonin secretion. The serotonin content in kiwifruit may also contribute to improved sleep, while the rich antioxidant content may suppress free radical expression and inflammatory cytokines. 

Folate deficiency has been linked to insomnia and restless leg syndrome; the folate in kiwifruit may improve folate status and, consequently, improve sleep. Although folates are widely consumed in the diet, they are destroyed by cooking or processing. As such, incorporating kiwifruit into the diet is a viable “food-first” alternative to melatonin supplements.

What future research should be done?

The absence of objective measures of sleep (eg, polysomnography, actigraphy) must be acknowledged as a limitation of the current study, but unfortunately, such measures were not feasible as the research was conducted during lockdown due to the global COVID-19 pandemic. This study should be replicated using a larger cohort of elite athletes incorporating a combination of subjective and objective measures of sleep and recovery in a randomized control trial.

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