The human brain and nervous system require nutrients like essential fatty acids, amino acids, vitamins, and minerals for proper functioning. Deficiency in these nutrients can lead to mental function changes before physical symptoms appear. For instance, depression, fatigue, and irritability can occur before the physical signs of scurvy, a vitamin C deficiency disease. People with mental disorders such as ADHD and bipolar disorder, as well as those under stress, have shown improvement in symptoms and mood after taking multivitamins and mineral supplements. Even healthy individuals have experienced better mental function and mood with these supplements, suggesting a link between mood symptoms and nutrient inadequacy.
Fruits and vegetables are rich in essential vitamins and minerals, particularly vitamin C and carotenoids. Recent studies have found that increased consumption of fruits and vegetables is linked to better psychological well-being and reduced depression. Kiwifruit, a rich source of vitamin C, also contains vitamins B, E, and K, carotenoids, and minerals like copper and magnesium. Since many of these nutrients are associated with improved mood, increased kiwifruit consumption may enhance mood, especially in individuals with low fruit and vegetable intake.
Eating kiwifruit daily has been linked to better sleep, but the reasons are unclear. One study looked at the immediate effects of fresh and dried green kiwifruit on sleep, mood, and urinary levels of serotonin and melatonin metabolites (1).
24 men (average age: 29 years, average BMI: 24) with either poor (12) or good (12) sleep quality participated in a randomized, single-blind crossover study. They consumed one of three treatments with a standardized evening meal: (1) two fresh green kiwifruits, (2) dried green kiwifruit powder mixed with water (equivalent to two fresh kiwifruits), or (3) water (control). Sleep quality, mood, and morning urinary levels of serotonin and melatonin metabolites, vitamin C, and B vitamins were measured (1).
Both fresh and dried kiwifruit improved morning alertness, sleepiness, and vigor compared to the control (p < 0.05). Mood improved slightly with both kiwifruit treatments. Urinary serotonin metabolite levels increased with both treatments compared to the control. In poor sleepers, waking up was 24% easier after dried kiwifruit (p = 0.005) and 13% easier after fresh kiwifruit (p = 0.052). Good sleepers found it 9% easier to fall asleep with fresh kiwifruit (p = 0.053). Poor sleepers had lower B vitamin levels compared to good sleepers (p < 0.05). This study showed that eating fresh or dried kiwifruit with an evening meal may improve sleep and mood, potentially through changes in serotonin metabolism (1).
Enhanced intake of fruit and vegetables has been associated with improved psychological well-being. One study investigated the potential mood-enhancing effects of kiwifruit. Young adult males (n= 35) were supplemented with either half or two kiwifruit/day for 6 weeks. Profile of Mood States questionnaires were completed at baseline and following the intervention (2).
No effect on overall mood was observed in the half a kiwifruit/day group; however, a 35 % (p = 0·06) trend towards a decrease in total mood disturbance and a 32 % (p = 0·063) trend toward a decrease in depression were observed in the two kiwifruit/day group. Subgroup analysis indicated that participants with higher baseline mood disturbance exhibited a significant 38 % (p = 0·029) decrease in total mood disturbance, as well as a 38 % (p = 0·048) decrease in fatigue, 31 % (p = 0·024) increase in vigor and a 34 % (p = 0·075) trend towards a decrease in depression, following supplementation with two kiwifruit/day. There was no effect of two kiwifruit/day on the mood scores of participants with lower baseline mood disturbance. Dietary intakes and body status of specific micronutrients indicated a significant increase in the participants' vitamin C intakes and corresponding plasma levels of the vitamin. The results indicated that enhanced intake of kiwifruit by individuals with moderate mood disturbance could improve overall mood (2).
Kiwifruit is highly nutritious, containing dietary fiber, vitamin C, and potassium. It is easy to eat by cutting it in half and is great for a quick snack. Kiwifruit has a brown, hairy skin. People usually eat kiwifruit without the skin, while in New Zealand, they eat it with the skin.
One study examined whether eating the flesh and skin of the kiwifruit together may be better off to control blood glucose levels. Twelve healthy volunteers participated. Eating kiwifruit with bread or before eating bread reduced the rise in blood sugar compared to eating only bread. There was no significant difference between eating of whole kiwifruit (pulp and skin, 92.4 g) and just the pulp (100 g). The highest blood sugar spike was reduced by 27.6%, and the overall blood sugar increase was reduced by 29.3%, even when only the pulp was eaten. The study showed that kiwifruit could lower blood sugar levels after meals, whether eaten with or without the skin (3). A whole golden kiwifruit with skin wights ~ 120 g. The participants in this study ate slightly less than a whole kiwifruit for the test.
Consumption of vitamin C-rich fruits and vegetables is linked to increased vitality. A study assessed the impact of kiwifruit consumption on subjective vitality and the role of vitamin C in this effect. The study involved 167 young adults (61.1% female, aged 18-35 years) with plasma vitamin C levels below 40 µmol/L. Participants were divided into three groups: kiwifruit (2 SunGold™ kiwifruits/day), vitamin C (250 mg tablet/day), and placebo (1 tablet/day). The study included a two-week lead-in, a four-week intervention, and a two-week washout period. Plasma vitamin C levels and vitality (total mood disturbance, fatigue, and well-being) were measured bi-weekly. Sleep quality and physical activity were tracked every second day via smartphone surveys, and a three-day food diary was used to assess nutritional confounds during each study phase (4).
Plasma vitamin C levels reached saturation within two weeks for both the kiwifruit and vitamin C groups. The kiwifruit group showed improvements in mood disturbance, significantly decreased fatigue, and improved well-being after two weeks, with well-being remaining high through washout. Vitamin C tablets improved well-being after two weeks and also improved mood and fatigue for those with low vitamin C levels during lead-in. Diet records indicated reduced fat intake for the kiwifruit group during the intervention. These effects were significant even after adjusting for group allocation, age, and ethnicity, and were not explained by sleep quality, physical activity, BMI, or other dietary patterns. The placebo group showed no changes in plasma vitamin C status or vitality. The study concluded that whole-food consumption of kiwifruit enhanced subjective vitality in adults with low vitamin C status, with similar but not identical effects observed for vitamin C tablets, suggesting additional properties of kiwifruit may contribute to improved vitality (4).
The primary vitality outcomes compared various study weeks. The kiwifruit group had significantly reduced total mood disturbance after two and four weeks of intervention, which returned to baseline during washout. The vitamin C group showed non-significant reductions in total mood disturbance, while the placebo group showed no changes. The kiwifruit group also showed reduced fatigue after two weeks but not four weeks. Fatigue increased significantly during washout for the vitamin C group, with no changes in the placebo group. Well-being significantly increased after two weeks of kiwifruit supplementation, remained high after four weeks, and did not decrease during washout. The vitamin C group showed a trend of increased well-being at the end of the intervention, which disappeared during the washout. The placebo group showed no significant changes in well-being except for a return to baseline levels between Study Weeks 4 and 6 (4).
Mood regulation can be complex, involving several mechanisms.
Vitamin C, a powerful antioxidant, helps reduce inflammation and aids in neurotransmitter production. Kiwifruit as a vitamin C-rich food reduces oxidative stress and inflammation, and the higher vitamin C levels are linked to better mood. Regular kiwifruit consumption increases vitamin C in the body.
Neurochemicals like serotonin from kiwifruit can also boost mood.
Kiwifruit contains other vitamins and polyphenols that may improve mood by reducing oxidative stress and enhancing metabolism.
Therefore, kiwifruit might improve mood by providing vitamin C and other nutrients, affecting neurochemical metabolism and oxidative stress. Better sleep related to regular kiwifruit consumption could also improve mood, and vice versa.
References:
1. Kanon AP, Giezenaar C, Roy NC, McNabb WC, Henare SJ. Acute effects of fresh versus dried Hayward green kiwifruit on sleep quality, mood, and sleep-related urinary metabolites in healthy young men with good and poor sleep quality. Front Nutr. 2023 Mar 14;10:1079609. doi: 10.3389/fnut.2023.1079609. PMID: 36998905; PMCID: PMC10043399.
2. Carr AC, Bozonet SM, Pullar JM, Vissers MC. Mood improvement in young adult males following supplementation with gold kiwifruit, a high-vitamin C food. J Nutr Sci. 2013 Jul 24;2:e24. doi: 10.1017/jns.2013.12. PMID: 25191573; PMCID: PMC4153016.
3. Inoue Y, Kitani Y, Osakabe S, Yamamoto Y, Murata I, Kanamoto I. The Effects of Gold Kiwifruit Intake Timing with or without Pericarp on Postprandial Blood Glucose Level. Nutrients. 2021 Jun 19;13(6):2103. doi: 10.3390/nu13062103. PMID: 34205359; PMCID: PMC8235107.
4. Conner TS, Fletcher BD, Haszard JJ, 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 Sep 22;12(9):2898. doi: 10.3390/nu12092898. Erratum in: Nutrients. 2022 Sep 30;14(19):4063. doi: 10.3390/nu14194063. PMID: 32971991; PMCID: PMC7551849.
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