(RxWiki News) If you really are what you eat, then what foods make the difference? Apparently, apples and oranges and broccoli and beans – if you want to feel calm and content each day.
That's the finding of a new study that looked at the link between individuals' moods and their intake of fruits and vegetables.
The study could not establish that eating fruits and vegetables caused people to feel happier.
The researchers simply found that the more fruits and vegetables college students ate each day, the happier mood they had that day and the next.
"Eat plenty of fruits and vegetables."
The study, led by Bonnie A. White, of the Department of Human Nutrition at the University of Otago in New Zealand,
The researchers recruited 281 young adults (average age 20) who tracked their food intake using an online food diary for 21 straight days.
The participants reported their positive and negative feelings and whether they ate any of five specific foods. They rated their emotions by using a scale of 1 (not at all) to 5 (extremely) for 18 different adjectives, nine positive and nine negative (nervous, depressed, cheerful, energetic, etc.)
For the food diary, the participants reported the number of servings they had had that day of fruit, vegetables, chocolate-coated or cream-filled cookies, potato chips/corn snacks/corn chips and cake/muffins/buns. Juices were excluded, and the participants were given information to properly measure a "serving."
The researchers then mathematically analyzed the relationships between the foods the participants ate and how they felt that day, as well as the next day. They adjusted their analysis to account for the participants' gender and weight.
The researchers found that the participants felt emotionally better on the days they ate more fruit and vegetables. They also tended to feel a little better the day after they ate fruits and/or vegetables.
A day of feeling a higher positive mood than a negative one was linked to about 0.112 more servings of fruit and 0.147 more servings of vegetables on average for each additional higher point on the mood scale.
The researchers determined that individuals would need to eat about seven to eight servings of fruits and vegetables each day to notice a "meaningful positive change," defined as at least 0.16 increase in the positive mood chart.
"On days when people ate more fruits and vegetables, they reported feeling calmer, happier and more energetic than they normally do," the researchers wrote. "They also felt more positive the next day."
Weight and gender had little effect, the researchers found.
"These associations held regardless of the body mass index [weight] of individuals, although the association for fruit consumption was stronger in men than women," the researchers wrote. "Both men and women benefited equally from vegetable consumption."
There were limitations to the study. It was an observation study, not an experiment, so the researchers cannot say that eating fruits and vegetables definitely caused the better moods.
It's also possible that, if there is a cause and effect involved, it's psychological rather than physical.
"In terms of mechanism, it is possible that eating behaviour may influence affect simply through psychological mechanisms. Perceptions of the health value of certain foods may lead a person to feel more positive following consumption of ‘healthy’ foods," the researchers wrote.
Because the study was conducted with college students, it may not represent a broader population of people. Also, the majority of the participants were a healthy weight. Only 21 percent were overweight, and only 6 percent were obese.
The study was published January 23 in the British Journal of Health Psychology. The research was funded by a University of Otago Research grant. The authors declared no conflicts of interest.