Eating more fruit and vegetables may make young people calmer, happier and more energetic in their daily life, new research from the University of Otago suggests.
Researchers from the department of human nutrition, investigated the relationship between day-to-day emotions and food consumption.
The study is published in the British Journal of Health Psychology today.
A total of 281 young adults, aged about 20, completed an internet-based daily food diary for 21 days. Before this participants completed a questionnaire giving details of their age, gender, ethnicity, weight and height. Those with a history of an eating disorder were excluded.
The participants rated how they felt using nine positive and nine negative adjectives. They were also asked five questions about what they had eaten that day.
Specifically, they were asked to report the number of servings eaten of fruit (excluding fruit juice and dried fruit), vegetables (excluding juices), and several categories of unhealthy foods like biscuits/cookies, potato chips and cakes and muffins.
Researcher Caroline Horwath said the results showed a strong day-to-day relationship between more positive mood and higher fruit and vegetable consumption, but not other foods.
"On days when people ate more fruits and vegetables, they reported feeling calmer, happier and more energetic than they normally did."
Dr Conner and her team ran additional analyses and found that eating fruits and vegetables predicted improvements in positive mood the next day, suggesting that healthy foods might improve mood.
These findings held regardless of the body mass index of the individuals.
"After further analysis we demonstrated that young people would need to consume approximately seven to eight total servings of fruits and vegetables per day to notice a meaningful positive change.
"One serving of fruit or vegetables is approximately the size that could fit in your palm, or half a cup."
Dr Conner said to get the amount needed to increase positivity, people should make half their plate at each meal vegetables and snack on whole fruit, like apples, during the day.
While this research showed a promising connection between healthy foods and healthy moods, further research was necessary and the researchers recommend the development of random control trials evaluating the influence of high fruit and vegetable intake on mood and wellbeing.