What teenagers eat and drink may have more to do with their emotional well-being than we realize. New research suggests that something as ordinary as eating fruit or reaching for a soda could be associated with their mental health over time.
In a study of more than 6,500 Australian teenagers, those who ate more fruit were less likely to develop elevated symptoms of depression and anxiety over three years. Meanwhile, teens who drank more sugary beverages were more likely to experience those symptoms.
The findings, published in Child and Adolescent Mental Health, add to growing research on the relationship between diet and mental health. However, the study doesn't prove that eating fruit prevents depression or that drinking soda causes anxiety.
Researchers from the University of Sydney followed 6,537 students who were about 13 years old when the study began. Over the next three years, the teens answered questions about their usual consumption of fruit, vegetables and sugary drinks, along with their emotional well-being.
The researchers found that each additional daily serving of fruit was associated with a 13% lower likelihood of developing elevated depression symptoms and a 7% lower likelihood of elevated anxiety symptoms.
The connection with depression was more consistent, while the anxiety finding was less certain in some additional analyses.
Sugary drinks showed the opposite pattern. Teens who reported drinking more soda, sports drinks and other sweetened beverages were more likely to develop elevated symptoms of both depression and anxiety. The association appeared in boys and girls, although it was stronger among boys, particularly for anxiety.
Interestingly, eating more vegetables wasn't significantly associated with either outcome once researchers accounted for other factors. That doesn't mean vegetables aren't important for health, only that this study didn't find the same relationship observed with fruit.
So why might fruit and sugary drinks be associated with mental health?
Researchers don't yet know. It's possible that differences in overall eating habits, family circumstances or other lifestyle factors help explain the findings. Mental health can also influence appetite and food choices, making the relationship difficult to untangle.
Although the researchers accounted for factors such as physical activity and family economic circumstances, they couldn't consider everything that might affect the results. The teens also reported their own eating habits, which may not always reflect what they actually consumed.
Another important distinction is that the study measured symptoms of depression and anxiety using questionnaires. It did not establish whether participants had been clinically diagnosed with either condition.
Still, following teenagers over several years offers a useful perspective. Many earlier studies have examined diet and mental health at a single point in time, making it harder to understand which came first.
The findings also build on previous research exploring how diet quality may relate to teen mental health. This study adds detail by examining fruit, vegetables and sugary drinks separately.
The research used data from the Health4Life project, supported by the Paul Ramsay Foundation, Australia's National Health and Medical Research Council and a research center focused on preventing mental illness and substance use. Several researchers received additional public research funding. Two authors disclosed leadership roles in educational health organizations, while others reported affiliations with Deakin University's Food & Mood Centre.