Adults low in dietary vitamin C can get a renewed zest for life by eating two kiwifruit a day for two weeks, according to new research.
The Otago University study recruited 167 participants between 18 and 35 years old who had low baseline levels of vitamin C.
The study was funded by Zespri but conducted independently.
Researchers divided the participants into three groups: a kiwifruit group, an equivalent vitamin C tablet group (250km), or a placebo-tablet group.
Participants were then asked to eat either two Sungold kiwifruit a day for four weeks or take a tablet, depending on their group.
Blood vitamin C levels and questionnaire measures of food, fatigue and well-being were measured fortnightly throughout the study.
Lead author Associate Professor Tamlin Conner said the results showed vitamin C levels in both the kiwifruit group and vitamin C tablet group increased to normal within two weeks, and there was no placebo effect.
One key finding researchers discovered, said Dr Conner, was the group taking kiwifruit reported extra benefits of vitality.
"Whole fruit had a broader range of benefits: lessening fatigue and improving mood and wellbeing across a wider number of people than we saw in the supplement group," she said.
"The vitamin C tablet did decrease fatigue and improve well-being to some extent for individuals with consistently low vitamin C levels leading up to the intervention. Interestingly, the benefits from consuming kiwifruit emerged in just two weeks."
Dr Conner said by raising vitamin C levels through whole foods like kiwifruit, people can also consume other active ingredients beneficial for both the body and brain.
"For example, kiwifruit has numerous additional vitamins and minerals that support health and are also high in dietary fibre, which is beneficial to the gut. There are important links between the gut and the regulation of mood.
"This could account for why kiwifruit benefited mood more than vitamin C tablets."
Co-investigator Professor Margreet Vissers said while links between vitamin C and physical functioning are well-documented, this study established a role for vitamin C in mental functioning.