Adolescents who eat unhealthily are more likely to develop mental health problems than those with good diets, a new study has found.
However, switching to a better diet could improve mental health, according to the Deakin University study, which was published today in the journal PLoS One.
The researchers analysed the diets and mental health of 3040 Australian teens aged between aged 11 and 18 years in 2005 and 2006 and then again two years later. They found that even after accounting for factors such as socio-economic status, smoking and weight, those with better diets tended to have better mental health after two years, while things deteriorated for those with poor diets.
“This is suggesting that for kids who aren’t getting enough nutrient-rich food, it’s predisposing them to to mental health problems,” said lead researcher Dr Felice Jacka from Deakin University’s Barwon Psychiatric Research Unit.
“This is the first study world wide to suggest the relationship is causal.”
The researchers also examined whether depression or other mental health problems were causing teens to make bad diet choices, but found that this was not the case.
“We looked the other way to see if mental health predicted diet and didn’t find any evidence at all,” said Dr Jacka. “The relationship only goes one way.”
The study also found that for teens suffering mental health problems, changing to a healthier diet improved their state of mind.
Dr Jacka said public health messages should include information about the role healthy eating plays in mental well-being.
“So much of the discussion around poor dietary practices, the food industry and marketing to children is very much focused on the obesity epidemic. That’s important but we need to be expanding our discussion about the impact of poor eating practices to encompass mental health as well,” she said.
Dr Jacka said the government should use its legislative powers to restrict access to and advertising of nutrient-poor processed foods.
Dr Tim Crowe, Associate Professor in Nutrition at Deakin University’s School of Exercise and Nutrition Sciences said very little research had been done examining possible links between diet and mental health.
“We know a healthy diet affects our physical performance but as far as diet and mental illness goes, we don’t know that much. One of the few areas that has been researched is Omega 3 fish oils and there’s some reasonable evidence to show that this can play a part in brain function,” said Dr Crowe, who was not involved in Dr Jacka’s study.
“What [this study] shows is that the key concept of having a healthy diet is not only good for us physically and in preventing a range of diseases, it’s good for our brain as well,” he said.
“We know our brain needs a lot of nutrients to run and function and well. You are not going to get as many of those nutrients from a very nutrient-poor diet.”