Around 10%-20% of adolescents globally suffer from a mental health condition, such as anxiety or depression, according to the World Health Organization. It's also been shown that half of all mental health conditions start by age 14. Given how important and formative adolescence is in a person's life, finding ways of protecting or improving mental wellbeing in children and young people is extremely important.

We already know how valuable good nutrition and diet are for physical health – which is why experts recommend we aim for five servings of fruits and vegetables a day ("five-a-day"). More recently research has also started to suggest that nutrition could influence mental health. While more research is still needed in this area, our recent study found found that eating a more nutritious diet, rich in fruit and vegetables, and having healthier breakfasts and lunch habits were associated with better mental wellbeing in children.

To conduct our study, we used data from the Norfolk Children and Young People Health and Wellbeing Survey. This collected data on mental wellbeing and different things that impact it – such as socioeconomic status and age – from children at over 50 schools in Norfolk. This allowed us to investigate the importance of fruit and vegetable consumption and meal choices (such as what students ate for breakfast or lunch) with mental wellbeing in this age group.

Our analyses looked at 1,253 primary school pupils aged 8-11 years and 7,570 secondary school pupils aged 12-18 years. Using different questionnaires for the two groups, we assessed their mental wellbeing by asking them them to score how often they had the feelings described in statements such as "I've been feeling good about myself" or "I've been feeling loved". The scores for each statement were added together to give a total score. The higher this total score is, the greater a child's mental wellbeing.

We also asked students questions on their age, gender, health, living situation and adverse experiences (such as being bullied, or experiencing arguing or violence at home) alongside questions about what kinds of foods they typically ate. This was important so that instead of investigating nutrition and wellbeing on their own, we were able to take into account other factors that can impact a person's wellbeing score. By doing this, we were able to show that the link between a healthier diet and better mental wellbeing still existed even after taking all these other factors into account.

Nutritious meals

In the secondary school group, higher fruit and vegetable consumption was associated with higher mental wellbeing scores – around 8% higher for those who ate five servings daily compared to those who ate none.

We also found that the wellbeing score varied depending on what type of breakfast or lunch participants ate. Compared to secondary school children who ate a conventional breakfast (such as cereal, toast or a cooked breakfast, like eggs), those who didn't eat any breakfast had an almost 6% lower mental wellbeing score. Those who consumed only an energy drink for breakfast had an almost 7% lower wellbeing score.

Scores were similarly low for those who didn't eat lunch compared to those who did. These associations were also similar in primary school children.

Our research also revealed that, on average, in a class of 30 secondary school children, four would have nothing to eat or drink before school, and three had nothing to eat or drink for lunch. We also found that only 25% of secondary school children ate five or more fruits and vegetables a day – and one in ten ate none.

These statistics would be concerning even without the link we have found with mental health, as poor nutrition is likely to impact on school performance as well as growth and development. While more primary school children ate breakfast and lunch, there was similarly poor fruit and vegetable intake.

To put our findings into perspective, having no breakfast or lunch was associated with a similarly detrimental effect on mental wellbeing as children witnessing regular arguing or violence at home. But as our study was observational, it's difficult for us to prove the cause of poor mental wellbeing until trials are done to explore these links, fully understand why they exist, and really be certain whether better nutrition will improve mental wellbeing in children.

Our findings show that good quality nutrition needs to be available to all children and young people to improve mental wellbeing and help them reach their full potential. To do this, we could encourage more funding for breakfast clubs, make sure that all children eligible for free school meals use them, and that these meals contain at least two portions of fruits or vegetables. To achieve this, these approaches need to be supported by school policies and public health strategies.

Ailsa Welch is Professor of Nutritional Epidemiology at University of East Anglia and Richard PG Hayhoe is Senior Lecturer in Public Health at Anglia Ruskin University. This article is republished from The Conversation under a Creative Commons license.