Kiwi fruit improves vitality and mood in as little as four days

Kiwifruit has proven itself as a powerful mood booster and new research from the University of Otago has shown just how fast its effects can be.

In a study, published in The British Journal of Nutrition, researchers found the furry fruit improved vitality and mood in as little as four days.

Co-author Professor Tamlin Conner, of the Department of Psychology, says the findings provide a tangible and accessible way for people to support their mental well-being.

“It’s great for people to know that small changes in their diet, like adding kiwifruit, could make a difference in how they feel every day.”

Vitamin C intake has been associated with improved mood, vitality, well-being, and lower depression, while vitamin C deficiency is associated with higher depression and cognitive impairment.

However, Professor Conner says limited research has assessed how quickly mood improvements occur after introducing vitamin C supplements or whole food sources.

The researchers aimed to fill that gap with an 8-week dietary intervention of 155 adults with low vitamin C.

Participants took daily either a vitamin C supplement, placebo, or two kiwifruit. They then reported their vitality, mood, flourishing, sleep quality, sleep quantity, and physical activity using smartphone surveys.

The researchers found kiwifruit supplementation improved vitality and mood within four days, peaking around 14-16 days, and improved flourishing from day 14. Vitamin C, on the other hand, marginally improved mood until day 12.

Lead author Dr Ben Fletcher, who conducted the research as part of his PhD at Otago, says understanding the nuances of when and how these effects occur day-to-day contributes to our knowledge of the potential benefits of vitamin C-rich foods and supplements on mental health.

“This helps us see that what we eat can have a relatively fast impact on how we feel.

“Our participants had relatively good mental health to begin with so had little room for improvement, but still reported the benefits of kiwifruit or vitamin C interventions,” he says.

He adds that, while vitamin C tablets showed some improvements, the study underscores the potential synergistic effects of consuming whole foods like kiwifruit.

“We encourage a holistic approach to nutrition and well-being, incorporating various nutrient-rich foods into your diet.”

In addition to the direct implications for individuals seeking to improve their mental well-being, Professor Conner says the study introduces a novel methodology in nutritional research.

“The use of intensive smartphone surveys offers a real-time understanding of the day-to-day changes in mood-related outcomes.”

Reference:

Fletcher BD, Haszard JJ, Vissers MCM, Conner TS. Smartphone survey data reveal the timecourse of changes in mood outcomes following vitamin C or kiwifruit intervention in adults with low vitamin C. British Journal of Nutrition. Published online 2023:1-13. doi:10.1017/S0007114523002787.