Eating the right amount of vegetables can improve mental health and happiness

When healthy adults consume the daily amount of vegetable servings recommended by the Dietary Guidelines for Americans (DGA) it has a positive effect on how happy the person feels, according to a study completed by scientists at the USDA's Agricultural Research Service (ARS).

Many studies show that eating the DGA-recommended daily amounts of fruits and vegetables is good for our general health, but only a few studies have demonstrated the role that vegetable consumption (separate from fruits) has on one's mental health.

A group of scientists at the Grand Forks Human Nutrition Research Center in Grand Forks, North Dakota, conducted an eight-week study to evaluate the impact of increasing daily vegetable servings to match DGA recommendations on how happy one perceives themself to be, a key measurement of psychological well-being.

The study divided healthy men and women between 18 and 65 years old into two groups. The first group of participants [the vegetable intervention group] received daily servings of DGA-recommended number and variety of vegetables, including dark green, red, and orange, and starchy vegetables, based on their energy needs during the course of the study.

The vegetable servings were minimally processed (raw and diced), making it simple for participants to include in their meals. The second group of participants [the control group] received the same number of interactions and attention from the researchers while maintaining a diet without adding vegetables.

All participants completed a questionnaire called the Subjective Happiness Scale (SHS). This is a subjective assessment that provides a mean overall score of a person's state of happiness based on the respondent's perspective. The study included measurements taken before and after the eight-week intervention.

"We observed an increased in SHS scores in participants from the group that followed the DGA recommendations for vegetable intake, whereas SHS scores stayed the same for the control group, who didn't change their diet," said ARS Research Biologist Shanon Casperson.

"Results suggest that increasing the amount of vegetables you eat every day may benefit your mental health," added Casperson.

The eight-week study was part of a parent study, a more extensive study conducted at the Grand Forks Human Nutrition Research Center that sought to determine whether adults with overweight and obesity would become more motivated to eat vegetables if they increased the number of servings they ate every day.

Unlike very tasty less healthy foods, which become more reinforcing if you eat them every day, increasing the amount of vegetables eaten daily does not make them more reinforcing, highlighting the difficulty of increasing vegetable consumption in adults. However, focusing on the benefits eating more vegetables has on psychological well-being may provide a more salient reason for people to increase their vegetable consumption.

The findings are published in The Journal of Nutrition.

More information:
Shanon L Casperson et al, Consumption of a Variety of Vegetables to Meet Dietary Guidelines for Americans' Recommendations Does Not Induce Sensitization of Vegetable Reinforcement Among Adults with Overweight and Obesity: A Randomized Controlled Trial, The Journal of Nutrition (2021). DOI: 10.1093/jn/nxab049

Provided by Agricultural Research Service