September 25, 2025, 10:55 am | Read time: 6 minutes

What we eat can influence our mood. For instance, regular consumption of junk food can lead to outbursts of anger. But can you simply “eat away” a bad mood with the right fruit? Researchers at the University of Otago in Dunedin, New Zealand, believe they have found the right food for this. Their study examined the impact of kiwis on mental health.

Areas Where Kiwi Impacts Humans

From a scientific perspective, the kiwi is a small fruit with an exceptionally large impact. It frequently becomes the focus of studies—especially in relation to sleep (kiwis apparently have sleep-promoting effects). Kiwi is rich in precursors of serotonin—often called the happiness hormone—which plays a crucial role in sleep regulation. But kiwi is also repeatedly linked to mood and mental health. This is due to its extraordinary nutrient composition, which seems to have an effect in this area as well.

What Kiwi Has to Do With Stress Management

Besides serotonin and its precursors, kiwis contain a lot of vitamin C and E, as well as polyphenols and flavonoids. These antioxidants protect cells from oxidative stress—a factor associated with anxiety, sleep disorders, and depression. Dr. Michael González and Dr. Jorge Miranda-Massari, both professors at the University of Puerto Rico with a keen interest in plant-based substances, argue that stress increases the need for certain nutrients and that insufficient intake of these nutrients can exacerbate the stress response. In 2012, they introduced their concept of “Metabolic Correction.”¹ It describes the targeted use of micronutrients to correct biochemical dysfunctions in the body. What does kiwi have to do with this?

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Study Situation

González and Miranda-Massari emphasize in their contributions the importance of antioxidants and B vitamins for stress management. Since kiwis are rich in both, they have come into focus as a food with therapeutic potential. The hypothesis is that kiwis can have a neuroprotective effect and thus promote mental health.

Improved Mood, Reduced Fatigue—Study With Young Men

But what has been concretely discovered so far? Among the earliest studies analyzing the impact of kiwifruit on mental health is a 2014 study published in the “Journal of Nutritional Science.”² The participants were 35 young men with low vitamin C levels. For the study, they consumed either half or two gold kiwis daily for six weeks and assessed their mood.

Based on the assumption that micronutrient deficiencies—especially vitamin C deficits—can exacerbate psychological symptoms like fatigue, irritability, and depressive moods, it was found that participants who consumed two kiwis per day experienced a 38 percent improvement in overall mood. Fatigue decreased by 38 percent, vitality increased by 31 percent, and the trend toward reducing depressive symptoms dropped by 34 percent.

Researcher Anitra Carr and her colleagues from the University of Otago (New Zealand) attributed the effects to the abundant vitamin C in kiwis: 116 milligrams of vitamin C per 100 grams of fruit. The plasma vitamin C levels also increased in the group consuming 2 kiwis daily.

However, this study only included men who self-assessed their mood via a questionnaire; there was no control group taking a placebo, and a comparison with a vitamin C supplement was missing.

Cambridge Researchers Studied Kiwi’s Effect on Women and Men With Low Vitamin C Levels

Perhaps the most relevant work on kiwi’s effect on mental health comes from researchers led by Benjamin Fletcher and Jillian Haszard from the University of Cambridge in 2022. They analyzed the effect of kiwi on a total of 155 women and men aged 18 to 35 with low vitamin C levels (below micromol per liter). Three groups were observed.³

• Group 1 ate two gold kiwis per day
• Group 2 took a daily vitamin C supplement (250 milligrams)
• Group 3 received a placebo containing no vitamin C

The study authors also explained that it was previously unknown how long it takes for the positive effect of kiwi on mental health to occur. To determine the timing of the effect, the study was conducted over eight weeks. Two weeks before and after the four-week intervention (consumption of supplements or kiwis), an introductory and washout phase took place, during which participants were examined but did not consume anything.

Participants were examined in person every two weeks. A fasting blood sample was taken to test vitamin C levels, and measurements of vitality, mood, and well-being were conducted. Additionally, participants reported every other day via a smartphone survey on vitality, mood, well-being, sleep quality, sleep quantity, and physical activity.

2 Gold Kiwis Daily Outperform Vitamin C Supplements in Mood Effects

After just four days, consuming kiwis led to an improvement in mood and vitality. The greatest effect was observed after 14 to 16 days. The vitamin C supplement slightly improved mood until the twelfth day. However, compared to the placebo group, the effect was not statistically significant.

The study concludes that kiwis can contribute to mood improvement even in a population with good mental health. The study authors suspect that other nutrients found in kiwis also contributed to the improvement in mental health. These included fiber, folic acid, and potassium.

Latest Kiwi Study: Mood Swings Reduced by 65 Percent

In April 2025, another kiwi study was conducted with 26 adults (18 to 60 years) with mild to moderate mood swings. They consumed two gold kiwis daily for four weeks compared to their usual diet. The most exciting result, besides the unsurprising increased vitamin C levels in the blood, was a significant reduction in overall mood swings by 65 percent.⁴

Why Do Studies Always Use Gold Kiwis?

Gold kiwis contain significantly more vitamin C than green kiwis (Actinidia deliciosa). Since the mentioned studies investigate the relationship between vitamin C levels and mood, the gold kiwi is the more effective test fruit. Additionally, they are less acidic and sweeter than green kiwis—making them more palatable and popular when participants have to eat the fruit over several weeks.

Vitamin C Content per 100 g

• Gold kiwi: approx. 160–180 mg
• Green kiwi: approx. 80–100 mg