Nearly a decade ago, a groundbreaking journal article written by a team of researchers including Professor Felice Jacka from Deakin University in Victoria introduced a radical new idea to psychiatry.
It may not have made the six o’clock news back then but it was the cover story for the American Journal of Psychiatry in March 2010 and it proposed that depression and anxiety were influenced by the quality of your diet.
In the 20 years preceding this moment, very few pharmaceutical advancements had been made outside mood stabilisers, and even they don’t help everyone. The standard view held by psychiatrists and pharmaceutical companies was to treat mental illness as a problem that occurred from the neck up. It was thought of as an imbalance of neurotransmitters like serotonin, GABA and dopamine in the brain. Hence the psychiatric medications targeting these neurotransmitters were the only treatment options.
But the pioneering Australian researchers found that mental health disorders were directly influenced by the quality of what you ate. They found that the body and the brain were in fact connected. While the role of diet in many other physical illnesses has been established, the exploration of diet and mental health in research is in its infancy. Today it’s called nutritional psychiatry.
The current standard Australian/American diet (SAD diet - how apt!) is literally killing us. Poor eating habits are the biggest driver of cardiovascular disease-related deaths around the globe. We are seeing rising levels of allergies, auto immune illnesses, autism and dementia and they too are connected to poor diet quality. Now, we are also finding that the development of depression and anxiety is influenced by what we eat. We really have to acknowledge that what we put in our mouths is going to affect how we feel.
Unpacking diet quality
The SAD diet is a diet high in trans fats, refined sugars, additives and preservatives. It’s low in fibre and is increasingly made up of ultra processed ‘food like’ products that have taken over supermarket shelves. Over 60% of foods on the supermarket shelves fall into the ultra processed category.
The diet which improves mental health outcomes is a modified Mediterranean diet. This diet is rich in whole grains, fruits, vegetables, legumes, nuts, seeds and healthy fats, including olive oil, avocado and fish. Eating moderate amounts of protein including eggs, red meat and poultry.
The diet and mood connection
So why does the SAD diet make us sad or anxious? There are many complicated biochemical links to how the diet influences mood, but to put things simply, here are just three of the many ways that diet influences mood:
Processed, poor quality diets are devoid of important vitamins and minerals that provide the body with the nutritional co-factors to make neurotransmitters that keep us feeling happy and well;
Low fibre, high additive diets damage the gut microbiome (the bacteria that live in your large bowel) and the gut is responsible for the immune-signalling molecules being produced. When we eat a diet high in processed food we create pro-inflammatory molecules, and inflammation is what leads to the development and progression of depression;
Eating a junk food diet has also been found to cause changes in brain function which leads to mental health problems. Shrinking of the hippocampus happens and this contributes to memory problems and the development of depression and/or anxiety.
Diet quality matters before our children are born
Since that breakthrough study there have been many more studies conducted that have looked at mental illness in kids and the clear link with diet quality. Researchers have found diet quality is really important in the early stages of life and directly affects mental health outcomes in kids. We now know that mum’s diet before conceiving, during pregnancy and in the postnatal stage also plays a critical role in the mental health outcomes of her children.
Children who eat a junk food diet in early life are more likely to develop depression and anxiety as they grow. We know the average age of onset of anxiety in children is now six and 13 for depression. Hence the importance of being very mindful of what we feed our children from the get go.
And all of this began with that article back in 2010. Almost a decade later and the quality of kids diets does make the six o’clock news. It’s amazing how fast the science is building upon that big idea and the awareness of the role nutrition plays in mental health is growing.