Whole fruit Vitamin C intake linked to feelings of vitality, finds study
A University of Otago study has shown adults low in dietary vitamin C can improve their feelings of vitality by eating two kiwifruits a day for two weeks.
Consumption of vitamin C-rich fruit and vegetables have been associated with greater feelings of vitality. However, these associations have rarely been tested in randomized controlled trials.
Therefore, researchers from Otago's Department of Psychology (Dunedin) and the Center for Free Radical Research in Christchurch ran a placebo-controlled intervention to test whether increasing vitamin C through whole fruit or tablets can improve feelings of vitality or zest for life.
The study is published in the open-access journal Nutrients.
The study highlights the advantages of ingesting vitamin C through whole fruits such as kiwifruit. Observed effects were more marked than in a matched population taking vitamin C predominantly through a supplement tablet.
They recruited 167 young adults between 18 to 35 years-old who had low baseline levels of vitamin C and randomly divided them into three intervention groups; a kiwifruit group(2 kiwifruit/day), an equivalent vitamin C tablet group (250 mg tablet/day), or a placebo-tablet group (1 tablet/day). The trial consisted of a two-week lead-in, four-week intervention, and a two-week washout. Blood vitamin C levels and questionnaire measures of mood, fatigue, and well-being were measured fortnightly throughout the study.
The following results were observed-
- Participants consuming kiwifruit showed significantly improved mood and well-being during the intervention period; improvements in well-being were sustained during washout.
- Decreased fatigue and increased well-being were observed following intake of vitamin C alone, but only for participants with consistently low vitamin C levels during lead-in.
- Diet records showed that participants consuming kiwifruit reduced their fat intake during the intervention period.
- Intervention effects remained significant when adjusting for age and ethnicity, and were not explained by sleep quality, physical activity, BMI, or other dietary patterns, including fat intake.
- There were no changes in plasma vitamin C status or vitality in the placebo group.
To summarize, the results showed vitamin C levels in both the kiwifruit group and vitamin C tablet group increased to normal within two weeks. There was no placebo effect. A key finding however was the extra benefits to vitality reported by the group taking kiwifruit.
"Whole fruit had a broader range of benefits; lessening fatigue and improving mood and well-being across a wider number of people than we saw in the supplement group. 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 2 weeks," says Tamlin Conner, lead author and an Associate Professor at the Department of Psychology, University of Otago, New Zealand.
Dr. Conner says by raising vitamin C levels through whole foods like kiwifruit, people can get other active ingredients that will benefit more systems in the body and brain.
"For example, kiwifruit has numerous additional vitamins and minerals that support health and are also high in dietary fiber, 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", he further adds.
The authors concluded that "Whole food consumption of kiwifruit improved subjective vitality in adults with low vitamin C status. Similar, but not identical, changes were found for vitamin C tablets suggesting that additional properties of kiwifruit may contribute to improved vitality."