It is commonly believed that eating a healthy diet can have psychological benefits. However, research into the exact mechanism behind these benefits is still necessary. One study examined the potential benefits of eating fruits and vegetables in a young adult population (Conner et al., 2017). This article will briefly review that study.
Methods
The participants in this study consisted of 171 young adults recruited from a University in New Zealand. Of these participants, 59 were randomly assigned to the control group, 57 were assigned to the ecological momentary intervention group (EMI), and 57 were assigned to the fruit and vegetable intervention group (FVI).
The procedure was as follows:
- Baseline assessments were taken on the first day measuring the following:
- Demographics:
- Age
- Gender
- Ethnicity
- Height and weight, BMI
- Smoking status
- Depressive symptoms, as measured using the 20-item Centre for Epidemiological Studies Depression Scale (CES-D)
- Anxiety symptoms, as measured using the 7-item Anxiety sub-scale of the Hospital Anxiety and Depression Scale (HADS)
- Demographics:
- That evening (and the following 13 evenings), between 7:00 PM and 1:00 AM, participants completed a survey on their phones asking about the following:
- Mood:
- Negative mood (sad, anxious, angry)
- Positive mood (relaxed, happy, enthusiastic)
- Vitality, as measured using a modified version of the 4-item energy/fatigue scale of the Rand 36-Item Short Form Survey (SF-36)
- Flourishing, as measured using a 3-item version of the 8-item Flourishing Scale, and flourishing behaviors, as measured using three additional questions tracking:
- Curiosity
- Creative activity
- Perceived motivation
- Mood:
- The next morning, the heights and weights of the participants were measured, as were fasting baseline blood samples measuring:
- Plasma vitamin C
- Total plasma carotenoids
- The intervention was then administered based on the group each participant had been assigned to for the following 13 days:
- Participants in the control group were instructed to maintain their normal diet
- Participants in the EMI group were sent text messages two times a day instructing them to increase their fruit and vegetable intake
- Participants in the FV group were given a bag of fruits and vegetables to eat over the following 13 days
- After the 13-day period was complete, another blood sample was taken from each participant, and participants also completed follow-up measures:
- Depressive symptoms, as measured using the 20-item Centre for Epidemiological Studies Depression Scale (CES-D)
- Anxiety symptoms, as measured using the 7-item Anxiety sub-scale of the Hospital Anxiety and Depression Scale (HADS)
- Finally, at the end of the study, a follow-up survey was administered asking participants about their beliefs regarding FV as well as candy and fried foods
Results
The following results were obtained:
- By the end of the intervention, participants in the FVI group were significantly happier than participants in the EMI group, because participants in the EMI group showed significantly decreased happiness over the study period
- Participants in the FVI group showed significant improvements in vitality, flourishing, and flourishing behaviors compared to the two other groups
- There were no significant differences in plasma vitamin C, total carotenoid levels, or psychological expectancies between the three groups by the end of the study
Altogether, giving participants fruits and vegetables to eat led to significant mental health enhancements compared to control and compared to sending participants text message reminders to eat fruits and vegetables.
Wrapping up
The results of this study show that giving participants fruits and vegetables to eat leads to psychological benefits. Interestingly, sending another group of participants text message reminders to eat fruits and vegetables appeared to have no effects in most cases, and even had negative effects in other cases. This suggests that eating fruits and vegetables is good for mental well-being, but that feeling autonomy over this choice is crucial to achieve the benefits. Future research should continue to examine whether this relationship holds for other healthy behaviors.
References
Conner, T.S., Brookie, K.L., Carr, A.C., Mainvil, L.A., Vissers, M.C.M. (2017). Let Them Eat Fruit! The Effect of Fruit and Vegetable Consumption on Psychological Well-Being in Young Adults: A Randomized Controlled Trial. PLoS One, 12(2), e0171206. doi: 10.1371/journal.pone.0171206.
