The two studies are based on data from around 1,800 West Australia adolescents from all backgrounds, whose health has been tracked by the Institute since birth, showed that these problems were less among teens with a healthier style of eating.

"We're showing a significant relationship between what children eat and their brain function, yet it's not being taken seriously," the Sydney Morning Herald quoted says Wendy Oddy, leader of nutrition studies at the Institute as saying.

"We don't have enough promotion of fruit and vegetables, but you can walk through a supermarket and see whole aisles devoted to sweets, soft drinks and refined breakfast cereals," said Oddy.

The research classified the children's diets into two eating styles -- a 'healthy' pattern high in fresh fruit and vegetables, whole grains and fish, and a 'Western' diet higher in saturated fat, refined sugar and salt, with more takeaway foods, confectionery, processed, fried and refined foods.

"Omega-3 fats are an essential part of the nervous system, and the theory is that when there's not enough in the diet, brain function is affected.

"This is something the omega-3 industry has latched on to with fish oil, but I think this misses the point that some plant foods like nuts also contribute some of these omega-3 fats," she said.

Other research has found that impulsive young adults are more likely to go for snack foods when they're hungry, for instance, while feeling depressed or emotionally distressed can drive preferences for eating sweet carbohydrate or fatty foods. There is also a link between being overweight and being depressed, said Oddy.

"Because we're seeing more overweight and obesity, I think we'll see more depression, although I don't know whether the depression comes first or the obesity.

"We also know that people who are overweight or obese have more inflammatory factors in their blood so it may be that this is having an effect on brain function," she added.

From the November 15, 2010, Prepared Foods E-dition