October 21, 2026, 8:03 am | Read time: 6 minutes
Research has long suggested that diet can be linked to mental health. A new study from Australia specifically examined adolescents in this context. It investigated over a three-year period how the consumption of fruits, vegetables, and sugary drinks affects the likelihood of developing mental health issues. The findings could potentially contribute to the development of prevention strategies in the future.
FITBOOK has frequently reported on the connection between the gut and the psyche: the so-called gut-brain axis, which is based on close communication through nerve pathways, neurotransmitters, and the microbiome. Diet is believed to influence mental health in various ways. For instance, the consumption of soft drinks is said to increase the tendency toward depression, while abstaining from meat may reduce it.1,2
Adolescent Years Crucial for Mental Health
The current study specifically focused on adolescents—a life stage that has a significant impact on one’s mental health.3 During this time, depression and anxiety disorders often first appear, the authors write. At the same time, many adolescents are allowed to make their own dietary choices for the first time since childhood. The researchers find it all the more important to understand whether and to what extent eating and drinking habits now influence the psyche.
Previous studies have already pointed to a connection between diet and mental health issues.4 However, the results regarding the impact of healthy foods like fruits and vegetables were often inconsistent. Moreover, most studies examine the links between diet and mental health at only a single point in time, according to the authors. Thus, data on the long-term impact of dietary habits are lacking. Possible differences between genders have also been scarcely considered. This is where the new study comes in.
Study Details
The researchers conducted a prospective longitudinal cohort study. They repeatedly examined a group of participants over an extended period to capture connections between earlier characteristics and later developments.
The data came from the Australian “Health4Life” study.5 Health information from a total of 6,537 adolescents from 71 secondary schools in Queensland, New South Wales, and Western Australia was included in the analyses. The average age of the participants at the start of the study was 12.65 years. The first survey took place in 2019, and the last one three years later. Thus, the participants were predominantly 12 to 13 years old at the beginning and 15 to 16 years old at the end.
Adolescents who already showed signs of depression or anxiety disorders at the start of the study or for whom baseline data were missing were excluded from the analysis.
Also of interest: Highly processed foods could harm the brain unnoticed
Recording Dietary Habits and Depression
In online questionnaires, the adolescents provided information about their usual fruit and vegetable consumption and how often they consumed sugary drinks. The researchers defined a serving of fruit as 150 grams, a serving of vegetables as 75 grams. For drinks, they used a quantity of 250 milliliters.
The authors recorded depression symptoms using the Patient Health Questionnaire for Adolescents (PHQ-A), a standardized questionnaire for assessing depressive symptoms in adolescents. For anxiety symptoms, they used the PROMIS Anxiety Pediatric Scale.6 This scientifically validated measurement tool captures anxiety complaints in children and adolescents based on their own reports.
Using established thresholds, the researchers distinguished between elevated psychological symptoms and lower levels. Additionally, they considered age, gender, family wealth as a measure of socioeconomic status, and physical activity in their statistical calculations to account for their potential influence on the results.
Results: More Fruit, Less Depression
In the evaluation, the authors found that a fruit-rich diet was associated with a lower risk of elevated depression and anxiety symptoms. Even after considering potential influencing factors, these observations remained. With each additional daily serving of fruit, the risk of developing elevated depression symptoms during the observation period decreased by 13 percent. For anxiety symptoms, the connection was somewhat less pronounced, with a difference of 7 percent.
In contrast, no statistically significant connection was found between vegetable consumption and depression or anxiety. Thus, the observations do not indicate that higher vegetable consumption reduces the risk of these complaints.
However, there was indeed a connection with sugary drinks—a reverse one. Adolescents who consumed more of them had a higher risk of depression and anxiety disorders. This connection was statistically significant for both genders, but it was particularly pronounced for anxiety in boys. For depressive symptoms, the connection was similarly pronounced between boys and girls.
It should be noted, however, that the researchers logarithmically converted the drink consumption—they mathematically altered the data before examining the connection. Therefore, the numbers cannot be directly interpreted as a risk increase from an additional glass of a sugary drink.
These Drinks Negatively Affect Mental Health
Sugary Drinks Increase the Risk of 7 Cardiovascular Diseases
Possible Significance of the Results
The results suggest that diet could be linked to the mental health of adolescents. Schools, families, and prevention programs could take this into account, the authors say, by promoting balanced dietary habits. Since the study not only considered general dietary quality but also examined individual food groups, potential starting points for health programs can be identified more concretely.
Particularly intriguing is the observed connection with sugary drinks. Especially since, as mentioned above, previous studies had already suggested such a link in adults. A possible explanation discussed is that high sugar consumption could influence the composition of the gut microbiome.
Limitations
Several limitations should be noted. A particularly significant one is that the adolescents’ dietary information is based on self-reports. This means that memory errors and inaccurate assessments cannot be ruled out. Additionally, only three dietary indicators were examined. Therefore, the results cannot provide a comprehensive statement about overall dietary quality.
This was an observational analysis. Thus, unconsidered influencing factors could also explain the observed connections, such as total daily energy intake, general dietary habits in the household, the mental health of the parents, and so on. Moreover, besides sugary drinks, there are other unhealthy dietary habits. It should also be noted that the participants were students at secondary schools. The sample thus consisted of socioeconomically better-off adolescents. The transferability of the results is therefore limited.
Finally, it should be noted that the questionnaires used for psychological complaints only provide possible indications. They do not allow for a clinical diagnosis. Therefore, the results refer to elevated symptoms—not confirmed depression or anxiety disorders.
In any case, the results should not be interpreted as indicating that fruit prevents depression or that sugary drinks cause mental illnesses. Nor does the study prove that a change in diet alone can treat existing complaints.