Smartphone survey data reveals the timecourse of changes in mood outcomes following vitamin C or kiwifruit intervention in adults with low vitamin C

Abstract

Abstract Vitamin C-rich foods can improve mood, however, the timecourse of these benefits are unknown. This study utilised intensive longitudinal smartphone surveys from a three-armed placebo-controlled trial to determine mood-related changes following supplementation with vitamin C (250 mg tablet/day), kiwifruit (2 SunGold™ kiwifruit/day), or a placebo (1 tablet/day). Secondary data was analysed from the KiwiC for Vitality trial (Trial ID: ACTRN12617001031358). Adults (n = 155, 63% female, aged 18–35) with low plasma vitamin C (<40 μmol/L) completed a 14-day lead-in, 28-day intervention, and 14-day washout. Participants self-reported vitality (SF-36), mood (POMS Total Mood Disturbance), flourishing (Flourishing Scale), sleep quality, sleep quantity, and physical activity every second day using smartphone surveys. Plasma vitamin C, measured fortnightly, reached saturation after two weeks of vitamin C or kiwifruit supplementation. Kiwifruit supplementation improved vitality and mood within four days, peaking around 14-16 days, and improved flourishing from day 14. Vitamin C marginally improved mood until day 12. Incremental area under the curve analyses revealed significant overall effects of kiwifruit consumption on vitality and mood compared to placebo, which were stronger than effects for vitamin C tablets, but attenuated when adjusting for covariates. Sensitivity analyses of participants with low baseline vitamin C status revealed improved mood (vitamin C and kiwifruit) and flourishing (kiwifruit only). This is the first study to use intensive smartphone surveys to model the day-to-day timecourse of mood-related states following vitamin C intervention and highlights the value of using smartphone surveys to reveal the temporal changes in mood-related outcomes following nutrient supplementation.