New research from New Zealand’s University of Otago shows that consuming more whole fruits and vegetables increases peacefulness, happiness and energy in one’s daily life. Scientists discovered the strong relationship to be particularly apparent in countering winter blues.

A total of 281 college-age students filled out an online food diary and mood survey for 21 consecutive days. Results showed that eating fruits and vegetables one day led to improvements in positive mood the next day, regardless of other key factors, such as body mass index. Other types of food did not produce the same uplifting effect.

“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,” says Tamlin Conner, Ph.D., with the university’s department of psychology. “One serving of fruit or vegetables is approximately the size that could fit in our palm, or half a cup.” Study co-author Bonnie White suggests that this can be accomplished by having vegetables comprise half of the plate at each meal and snacking on whole fruit like apples.

The American Psychiatric Association acknowledges that seasonal affective disorder (SAD) affects, at least mildly, as many as 20 percent of Americans.