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Why diet is important for mental and brain health

Why diet is important for mental and brain health
FELICE JACKA: If you have a mental disorder, say for example major depression, or schizophrenia, bipolar disorder, you are at increased risk for chronic physical diseases– so cardiovascular disease, heart disease, diabetes, obesity. These sorts of diseases are much more common in people who have mental disorders. And as soon as you have a mental disorder, it puts you at risk of those disorders even if they haven’t already occurred. But similarly, if you have heart disease or diabetes or obesity, you’re more at risk of particularly depression. Now, we think that that’s because of these common underlying pathways that influence both physical and mental health and that are, in turn, very clearly influenced by the quality of the food that we eat.
So one of the key concepts is this idea of inflammation. So our immune system is designed to sprint into action if we have an injury or if we have a severe infection and to repair us. But there’s a lot of things in our modern Western diet and also lifestyles that can create this low-grade chronic activation of the immune system. And that’s called inflammation. And the molecules that are released as part of that are actually directly thought to influence the risk for heart disease, cancer, and also depression. So that’s one thing the immune system– we think this is really important. And linked to that is oxidative stress. This is part of our body’s natural repair process.
But we need our own antioxidant defences to protect ourselves and to keep us well. And that is our brain as well as our body. There’s also other aspects of our health that we are increasingly understanding. And this relates to the gut. So the gut seems to be the engine of our immune system. It trains our immune systems when we’re babies, and it continues to play a critically important role through life. And then there’s this bi-directional communication between the gut and the brain. Most of the signals go to the brain, but about 10% go to the gut. So when we’re stressed, it affects our gut. And when our guts not so happy, it can affect our mental health.
Another thing we’re very interested in is this idea of brain plasticity. So 10 or 15 years ago, neuroscientists worked out that there’s a part of the brain that actually puts on new neurons throughout life. It’s called the hippocampus. It’s key to learning and memory. And it’s key also to mental health. And diet has a very direct effect on hippocampal volume and in its function and brain plasticity. Right at the other end of life, if we think about the need to preserve our brain health and our ability to learn and remember, the hippocampus is so important. I mean, it’s important right at the start of life as well.
But as we age, critically important to preserving our memory and our abilities to think. And we’ve shown and others have shown there’s very, very clear links between the quality of our diets and the size of our hippocampus independent of all of these other factors that we take into account. So there’s many ways in which diet influences these underlying shared risk factors for mental and physical health. And because again diet is modifiable, it’s a key target for us to think about prevention and treatment.

Observational evidence points to strong links between dietary intake and mental health symptoms.

There are several close co-morbid links between mental and physical health:

  • Individuals with serious mental disorders have a significantly increased risk of cardiovascular diseases, diabetes, and even some cancers.
  • Individuals with depression are also at an increased risk for cardiometabolic disorders, such as obesity, diabetes and heart disease, while those disorders – in turn – increase the risk of depression.
  • Individuals with gastrointestinal disorders are much more likely to have a higher prevalence of adverse mental symptoms, such as depression and anxiety.
  • Individuals with depression commonly report gastrointestinal symptoms such as diarrhoea, constipation and bloating.

Your task

Watch the interview with Professor Felice Jacka at the start of the Step, discussing the known mechanisms that link dietary intake and mental and brain health.

As you watch, consider the following question:

  • What do you think about the physiological mechanisms explaining the impact of diet on mental and brain health?
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Food and Mood: Improving Mental Health Through Diet and Nutrition

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