How Your Diet Affects Your Mental Health

An interview with the world-renowned expert in the way food choices impact depression and other mood disorders

For this month’s episode of my podcast, Eat Move Think, I interviewed Dr. Felice Jacka, the global expert in the way our diet affects our mental health. Dr. Jacka also is the author of Brain Changer: The Good Mental Health Diet. She’s a psychiatric epidemiologist from Australia’s Deakin University, where she runs the Food and Mood Centre. And she’s almost single-handedly created one of the hottest fields in wellness today: the area of nutritional psychiatry.

We’re all familiar with the way people can feel irritable and tired if they go too long without food. Dr. Jacka’s research indicates the relationship with what we eat is deeper than that. Her studies suggest that our food choices may be able to lift the symptoms of depression, as well as other mental illnesses.

I spoke with Dr. Jacka by phone. Following are some key points, but do check out the entire episode on Apple Podcasts, or your favourite podcast platform—and please do subscribe and rate the podcast as well.

This interview condensed and synthesized for length.

Shaun
Hi Felice, thanks for coming on the podcast. We’ve known for a long time that food affects our short-term mood. So why is it only recently that we’re starting to investigate the connection between eating patterns and mental health disorders. What took so long?

Felice Jacka
Look, I think there are couple of reasons. You have Cartesian dichotomy of mind and body as being separate, which we know is very much incorrect. We’re a highly complex, highly integrated system. And more recently, we’ve had these insights around the microbiota, and the critical role they play in virtually every physiological process in the body, including the health of the brain.

But to influence clinical practice, you need those intervention studies. And you need level one evidence, which are meta-analyses of intervention studies. The field itself is less than a decade old. So it takes time, but I really think there’s a new recognition and a push to look at what we call lifestyle psychiatry. In 2015, the Royal Australian-New Zealand College of Psychiatrists released their updated clinical guidelines for the treatment of mood disorders. Which suggest, step zero before you consider pharmacotherapy or psychotherapy should be, essentially, lifestyle medicine. Dietary behaviors, exercise, smoking cessation, sleep hygiene, those sorts of things. But of course, this is not what’s taught in medical school. And many physicians don’t feel adequately trained to be able to offer these types of interventions. So there’s a new interest in—a new appetite for this.

Shaun
What diet is the scientific evidence suggesting is best for mental health? Is it the Mediterranean diet? Something else?

Felice Jacka
Well, there are many different forms of healthy diet across the world. The Mediterranean diet is certainly the most studied, and the dietary pattern that has by far the largest and strongest evidence base for health benefits, from cardiovascular health to cancer to obviously diabetes, but also dementia as well as depression. There are many other forms of healthy diet—so for example a healthy Norwegian diet. It’s very high in cruciferous vegetables, sea food and root vegetables. Healthy Japanese diets. Healthy Chinese diets—high again in vegetables and fish.

Across the globe, we know what a healthy diet comprises. It should be high in a diverse range of plant foods. Good quality protein—so ones that come from unprocessed sources. Good quality fats are those that avoid saturated fats and focus on poly- and monounsaturated fats. But there’s a great deal of latitude there for individual variation, cultural variation, individual preference. Some people choose to eat meat, others don’t. You know, there are many different ways of approaching things. But as long as the diet is plant predominant then you are going to be doing better than the vast majority of people. I mean, in the US, nearly 60% of average energy intake comes from ultra processed food products. Nearly 60%! And we’re at a situation now, where about 60% of children alive today in the US will be clinically obese by the time they’re 35.

Shaun
It’s amazing that the same food that helps us prevent cancer, diabetes, heart disease, and Alzheimer’s appears also to improve your mood. Are these all connected?

Felice Jacka
Yeah, completely. If you get back to the root cause, we’re starting to believe now that it sits in the gut. We understand that the microbiota, the bacteria, with which we have co-evolved since the beginning, play an incredibly important role in our health. So very simply speaking, what bacteria in the gut do is—they digest dietary fiber. So the foods that your human enzymes can’t break down, the things that are found in fruits and vegetables, in whole grains, cereals, and legumes, nuts and seeds—the bacteria in the gut break these down through a process of fermentation. In doing so, they release a vast range of metabolites. And these metabolites we now know interact with every system in the body. They profoundly influence the immune system. They influence brain plasticity. They play a very important role in the brain development of infants.

And if you look at the incredible rise in allergic disease around the globe, particularly in western countries, over recent decades, we think that this is linked back to poor diet, and the gut, because the gut can’t do what it’s supposed to do without dietary fiber. And we don’t eat anywhere near enough dietary fiber. And this leads to all sorts of really problematic changes that flow through the health of the body, including the brain.

Shaun
Do you think we’ll get to a point where we can modify diet to target specific mood or mental disorders?

Felice Jacka
There’s a lot of interest in what’s called the ketogenic diet, which is pretty much the opposite of a good gut diet. Unfortunately, it is being promoted as a panacea for just about everything, on the basis of little to no evidence and certainly no long-term safety data. Based on everything we know so far, it’s likely to be noxious to the gut and, therefore, problematic to health. But we also have emerging evidence that for really serious psychiatric diseases, [keto] may be helpful. And so we’re about to start a pilot study to look at that in humans in an inpatient unit, people with psychosis, to see whether we can see a signal for efficacy.

Shaun
Let me just ask you one last question. Where do you see your field going? And what new discoveries might we anticipate?

Felice Jacka
It’s a really important question. I set up the Food and Mood Centre two years ago. It’s unique in the world, and it’s focused on nutritional psychiatry research. What we have at the moment is a very good and robust evidence base about the efficacy and the effectiveness of exercise in mental health. And not just in depression, but also in schizophrenia, and also on brain health and the problems that are associated with mental health problems. We need an equivalent base in diet.

The work on the gut I think is is critical. We now know that you can change the gut and its health within a few days by changing your diet. It’s amazing how rapidly it can change.

We’re about to start a clinical trial on FMT for depression. So this is fecal microbial transplant or, in simple terms, poo pills. For people with major depressive disorder because for people who have a very, very unhealthy gut, it may be that this is a useful way to actually increase the health of the gut, and thus alleviate symptoms.

But to my mind, the most interesting and exciting [area] is looking at the potential of big data. We’re collecting data from a very large, highly representative sample of humans across the age range—their lifestyle behaviors, diet, psychiatric health, microbiome, their oral and their fecal microbiome, and their blood. And what we’re starting to understand is, if you put all of that information together, you start to come up with algorithms that can predict people’s risk of disease. And may even start to say, okay, for you, you need this dose of this, you need less of this and more of that. And for the next person, you need something different. So this personalized medicine, personalized nutraceutical, and personalized nutrition is, really, I think, the Holy Grail and where the field is heading.

Medcan has launched a new program for the treatment of depression based on Dr. Felice Jacka’s SMILES trial. It’s a 12-week program that combines anti-inflammatory nutrition counseling with cognitive behavioral therapy to help people manage their depression and improve their mental and physical well being. To find out more, call (416) 862-1553, or email us at nutrition@medcan.com.

Shaun Francis is Medcan’s CEO and chair. Follow him on Twitter @shauncfrancis. Connect with him on LinkedIn. And follow him on Instagram @shauncfrancis

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