Junk food diets contribute to a range of negative health issues, from diabetes to heart conditions. Now, reports Beverly Hadgraft, they are also being linked to a rise in mental illness.
Psychiatric researcher and Associate Professor Felice Jacka of Victoria’s Deakin University has been at the forefront of studies into the links between diet and mental illness for 10 years.
Her findings have convinced her that junk food isn’t only wrecking our physical health – it’s wrecking our mental health as well. That’s the bad news. The good news is that switching to a healthy wholefood diet could help reduce the development of depression by as much as 50 per cent.
Professor Jacka is hoping her latest study will show it’s even possible to cure depression with a good diet. Her interest in the area began when she first entered psychiatry research in 2004 and was intrigued to realise how little interest there had been in the area of nutritional psychiatry.
“There were studies coming out of America [at the University of California] showing pretty clearly that unhealthy diets were damaging important proteins in the brain, while healthy fats and foods high in antioxidants were protective,” she recalls.
The links between depression and immune dysfunction and genetics were also becoming clear – and it was known that diet was a driver of both.
Professor Jacka, now President of the International Society for Nutritional Psychiatry Research, set up a study examining the influence of diet on depression in a large group of Australian women. After taking issues such as education, physical activity and socio-economic status into account, the results were extraordinary. Women who ate a processed-food diet were 50 per cent more likely to have a depressive disorder than those who ate a high-quality whole food one.
The findings generated huge international interest – and more massive studies backed up her finding.
One such study, looking at 3500 British civil servants, found those eating high-fat, high-sugar foods were 58 per cent more likely to develop depression than their healthy eating counterparts.
And a second study, of 10,000 middle-aged Spanish university graduates (initially set up to examine physical health symptoms), found a Mediterranean-style diet was hugely beneficial in preventing mental disorders, while a fast-food diet increased depression risk.
One American study of older African- Americans even found dietary counselling was as effective as psychotherapy in preventing depressive symptoms from developing into full-blown clinical depression.
These kick-started a wealth of other studies all over the world, which invariably replicated the same results. “Diet matters to depression,” Professor Jacka insists.
“Better-quality diets are consistently associated with reduced depression, while diets high in processed foods are associated with increased depression and often anxiety.
Worryingly, this seems to be the case right from the start of life.”
THE ILL-EFFECTS: FROM PREGNANCY TO CHILDHOOD and BEYOND
“We led a very large study of more than 20,000 mothers and their children that showed the children of mothers who ate an unhealthier diet during pregnancy had higher levels of behaviours that are linked to mental disorders,” says Professor Jacka. “This is consistent with what we see in animal experiments, where unhealthy diets fed to pregnant animals result in many changes to the brain and behaviour in offspring. This is very important to understand if we want to think about preventing mental disorders in the first place.
“The next steps are to systematically and scientifically examine the possible role of dietary factors in more serious mental illnesses, such as schizophrenia.”
There is also evidence that nutritional counselling could help reduce Alzheimer’s.
Professor Jacka is just completing the first-ever study in the world to see if changing diets can actually help cure existing depression.
She has plans for another study to see if probiotics could also be a depression cure. There has never been a more important time for her work. In the 20 years between 1986 and 2006, data from the US and UK found the percentage of young people suffering frequent anxiety and depression had doubled.
Something else doubled during that period – weight due to a processed-food diet. This is particularly distressing since, as the Professor explains, the average age for the onset of anxiety is just six, for depression it’s 13 and once children develop these conditions, they can become recurrent life-long issues.
For those parents who do insist that their children eat up all their broccoli, there’s reinforcement for this from the Murdoch Childrens Research Institute. It found that 11- to 14-year-olds on healthier diets were much happier, with less depression, whereas those with higher intakes of unhealthy foods were more likely to suffer depression. Again, this took into account a range of other issues, from family conflict to demographics.
Another Victorian study of adolescents, which found takeaway food was related to worse mental health, also found that improvements to diet over two years led to better mental health – even when no other changes were included.
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