Gut reactions

The benefits of eating well for our general health and performance are now well documented. However, the latest Deakin research shows that a good diet is just as important for mental health.

Most psychiatrists would have had no idea of a connection between mental health and diet only ten years ago, but ground-breaking research is currently transforming the profession’s understanding of how food and the brain interact.

“Researchers are only at the cusp of this knowledge,” said Associate Professor Felice Jacka, from Deakin’s School of Medicine. “But interest from researchers around the world has exploded over the past three years.”

Associate Professor Jacka has spearheaded much of this interest. Since publishing her “breakthrough” paper linking diet with depression and anxiety in the “American Journal of Psychiatry” in 2010, she has established and become president of the International Society for Nutritional Psychiatry Research in 2012 and is now conducting a rigorous “world first” randomised controlled study that examines how people with depression respond to improved diets.

The project has been funded by the NHMRC and will also look at the biological pathways between food and the brain that affect mental health, including the potentially important roles of inflammation and the gut in mental health. The research follows on from rat studies that have shown dietary changes can have a rapid impact on behaviour via changes to the composition of the microbiota that live in the gut.

“We are discovering that the gut microbiota may have an impact on mental health,” said Associate Professor Jacka.

Formerly known as “gut flora,” microbiota consists of tens of trillions of microorganisms, including 1000 different types of bacteria that live in our intestines. Two thirds of our microbiota are specific to each individual.

Further research, currently in the planning stages, will also test the theory that a “leaky gut” can contribute significantly to psychiatric disorders. It has been suggested that unhealthy diets can weaken the mucosal lining of the stomach, which, in a healthy person, should stop the contents of the gut from leaking into the body and affecting the immune system.

“We believe that people with chronic depression, for instance, could be experiencing increased immune responses to bacteria from the gut that has got into the bloodstream. Their body could be creating an immune response to those bacteria that contributes to depression,” she said.

Associate Professor Jacka added that the available evidence suggests that poor diets may be having a similar impact worldwide on mental health and on physical health. “Research is suggesting that the prevalence of psychological disorders, especially in young people, is increasing,” she said. “This apparent increase in poor mental health parallels worldwide increases in obesity rates, which have doubled since the 1980s”.

As one indication of the impact of unhealthy lifestyle across the world, in 2011 the head of the World Health Organisation estimated that the impact of unhealthy food and tobacco on physical health could cost the global economy $30 trillion by 2020.

The extent that better diets could improve mental health issues in the long-term is still unknown. However, Associate Professor Jacka predicts that future treatment for illnesses as varied as schizophrenia, autism, bipolar disorder and depression are likely to increasingly focus on diet.

So what constitutes a healthy diet?

“The key is to eat nutrient-dense and unprocessed foods,” said Professor of Psychiatry, Michael Berk, from Deakin’s School of Medicine. “These can be found in traditional diets, whether these be western, Japanese, Mediterranean or any other traditional diet.

 “Currently, we are recommending that people with mental health issues continue traditional treatments, but they can also try adding a healthier diet and regular exercise to their treatment regimen.”

If you are over 18, suffer from depression and would like to participate in this Melbourne-based trial, please contact: diet@barwonhealth.org.au or phone 03 4215 3325.