An apple a day may keep the psychiatrist away. That’s the conclusion of new research showing people who eat more fruits and vegetables are “calmer, happier, and more energetic” than those with poorer dietary habits.

The study, by researchers at New Zealand's University of Otago, suggests consuming at least seven daily servings of fruits and veggies is optimal in boosting a person’s mood and overall mental outlook.

"On days when people ate more fruits and vegetables, they reported feeling calmer, happier and more energetic than they normally did," said Tamlin Conner, M.D., an Otago Department of Psychology researcher who helped conduct the study, published in the British Journal of Health Psychology.

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Dr. Connor added that while the research shows a promising connection between healthy foods and positive moods, further research is needed to determine what’s behind the association and whether diets that are very high in fruits and vegetables can promote a sense of well-being.

For the study, 281 young adults maintained a food diary for 21 consecutive days, detailing what they had eaten and how they were feeling. Specifically, participants 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/muffins.

The results showed a strong correlation between positive moods and higher fruit and vegetable consumption, but not other foods.

"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,” said Dr. Conner. “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."