KiwiC for Vitality Study: Effect of kiwifruit on Vitality, Fatigue and Wellbeing

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The purpose of the study is to assess the effect of adding SunGold kiwifruit to the diet on changes in vitality, fatigue, and wellbeing. The study aims to determine whether any improvements in these outcomes can be attributed to the high vitamin C content of the fruit. In a previous pilot study, we observed that intake of two kiwifruit/day for six weeks provided a significant 31% increase in vigour and a significant 38% decrease in fatigue in young men with a higher than average total mood disturbance score as assessed by the Profile of Mood States (POMS) questionnaire. Interestingly, intake of half a kiwifruit/day did not have any effect on mood scores, suggesting a dose dependency. We are now proposing a larger study that includes both men and women, has more extensive measures of vitality, fatigue and wellbeing, and includes a vitamin C and a placebo comparison arm. This randomised controlled trial brings together the expertise of Professor Margreet Vissers, Dr Anitra Carr and Dr Tamlin Conner, New Zealand's leading research experts in vitamin C bioavailability and function (Vissers and Carr) and psychological wellbeing (Conner). We will recruit participants who have low vitamin C status. Individuals will be randomised to one of three interventions: (1) Two SunGold kiwifruit per day; (2) vitamin C tablet daily (equivalent to the vitamin C content of two kiwifruit); (3) placebo tablet daily. We will monitor vitality/fatigue/wellbeing, using intermittent nightly smartphone surveys and traditional fortnightly assessments. The study will last for 8 weeks (2 week lead-in; 4 week intervention; 2 week washout period). Our hypothesis is that consumption of two SunGold kiwifruit per day will improve vitality, decrease fatigue, and improve wellbeing.