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Open AccessArticle

KiwiC for Vitality: Results of a Randomized Placebo-Controlled Trial Testing the Effects of Kiwifruit or Vitamin C Tablets on Vitality in Adults with Low Vitamin C Levels

1
Department of Psychology, University of Otago, Dunedin 9054, New Zealand
2
Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch 8140, New Zealand
3
Department of Pathology and Biomedical Science, University of Otago, Christchurch 8140, New Zealand
4
Department of Human Nutrition, University of Otago, Dunedin 9054, New Zealand
*
Author to whom correspondence should be addressed.
Nutrients 2020, 12(9), 2898; https://doi.org/10.3390/nu12092898
Received: 13 July 2020 / Revised: 14 September 2020 / Accepted: 18 September 2020 / Published: 22 September 2020
(This article belongs to the Special Issue Vitamins C and D: Global and Population Health Perspectives)
Consumption of vitamin C-rich fruit and vegetables has been associated with greater feelings of vitality. However, these associations have rarely been tested in randomized controlled trials. The aim of the current study was to test the effects of eating a vitamin C-rich food (kiwifruit) on subjective vitality and whether effects are driven by vitamin C. Young adults (n = 167, 61.1% female, aged 18–35) with plasma vitamin C <40 µmol/L were randomized into three intervention conditions: kiwifruit (2 SunGold™ kiwifruit/day), vitamin C (250 mg tablet/day), placebo (1 tablet/day). The trial consisted of a two-week lead-in, four-week intervention, and two-week washout. Plasma vitamin C and vitality questionnaires (total mood disturbance, fatigue, and well-being) were measured fortnightly. Self-reported sleep quality and physical activity were measured every second day through smartphone surveys. Nutritional confounds were assessed using a three-day food diary during each study phase. Plasma vitamin C reached saturation levels within two weeks for the kiwifruit and vitamin C groups. Participants consuming kiwifruit showed significantly improved mood and well-being during the intervention period; improvements in well-being were sustained during washout. Decreased fatigue and increased well-being were observed following intake of vitamin C alone, but only for participants with consistently low vitamin C levels during lead-in. Diet records showed that participants consuming kiwifruit reduced their fat intake during the intervention period. Intervention effects remained significant when adjusting for age and ethnicity, and were not explained by sleep quality, physical activity, BMI, or other dietary patterns, including fat intake. There were no changes in plasma vitamin C status or vitality in the placebo group. Whole food consumption of kiwifruit improved subjective vitality in adults with low vitamin C status. Similar, but not identical, changes were found for vitamin C tablets suggesting that additional properties of kiwifruit may contribute to improved vitality. View Full-Text
Keywords: Vitamin C status; energy; well-being; kiwifruit; mood Vitamin C status; energy; well-being; kiwifruit; mood
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MDPI and ACS Style

Conner, T.S.; Fletcher, B.D.; Pullar, J.M.; Spencer, E.; Mainvil, L.A.; Vissers, M.C.M. KiwiC for Vitality: Results of a Randomized Placebo-Controlled Trial Testing the Effects of Kiwifruit or Vitamin C Tablets on Vitality in Adults with Low Vitamin C Levels. Nutrients 2020, 12, 2898. https://doi.org/10.3390/nu12092898

AMA Style

Conner TS, Fletcher BD, Pullar JM, Spencer E, Mainvil LA, Vissers MCM. KiwiC for Vitality: Results of a Randomized Placebo-Controlled Trial Testing the Effects of Kiwifruit or Vitamin C Tablets on Vitality in Adults with Low Vitamin C Levels. Nutrients. 2020; 12(9):2898. https://doi.org/10.3390/nu12092898

Chicago/Turabian Style

Conner, Tamlin S.; Fletcher, Benjamin D.; Pullar, Juliet M.; Spencer, Emma; Mainvil, Louise A.; Vissers, Margreet C.M. 2020. "KiwiC for Vitality: Results of a Randomized Placebo-Controlled Trial Testing the Effects of Kiwifruit or Vitamin C Tablets on Vitality in Adults with Low Vitamin C Levels" Nutrients 12, no. 9: 2898. https://doi.org/10.3390/nu12092898

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