An increase in fruit and vegetables in our diet can make us calmer, happier and more energetic in daily life, new research from New Zealand’s University of Otago published in the British Journal of Health Psychology suggests.
Department of Psychology researchers Dr Tamlin Conner and Bonnie White, and Dr Caroline Horwath from Otago’s Department of Human Nutrition, examined the connection between day-to-day emotions and food consumption.
281 individuals [average age: 20 years] filled out an internet-based daily food diary for 21 consecutive days. Details of the participants like their age, gender, ethnicity, weight and height were collected through a prior questionnaire. This was done to screen out those with eating disorders.
Every evening, on each of the 21 days, participants recorded their feelings using nine positive and nine negative adjectives. They also answered five questions about what they had eaten that day, particularly the number of servings fruit [excluding fruit juice and dried fruit], vegetables [excluding juices], and unhealthy foods like biscuits/cookies, potato crisps, and cakes/muffins.
The results revealed a pattern suggesting 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,” says Dr Conner.
To test this causality, Dr Conner and her team analysed the diaries further and discovered that eating fruits and vegetables predicted improvements in positive mood the next day, suggesting that healthy foods may improve mood. These findings were valid irrespective of the BMI of 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. My co-author Bonnie White suggests that this can be done by making half your plate at each meal vegetables and snacking on whole fruit like apples,” says Dr Conner.
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