Gut Health Gurus Blog

Food, Mood and Mental Health

Food, Mood and Mental Health
healthy diet and depression

Millions of people around the world suffer from depression but what if I told you that new data is emerging that shows that mental health is directly correlated with what we eat?

I had the pleasure of speaking with Professor Felice Jacka. She is the director of the Food and Mood Centre at Deakin University in Australia, which is focused on Nutritional Psychiatry. She is also the President of the International Society for Nutritional Psychiatry Research and the past president of the Australian Alliance for the Prevention of Mental Disorders. She has performed studies that link depression and diet (Hint: it is much more correlated than we once knew!) 

Read on to learn about how you can improve your depression by what food choices you make, why a healthy diet is a cheaper option than one might think, easy ways to implement these strategies at home, and much more!

What Got You Interested in Studying Nutritional Psychiatry?

My first degree was in finance and I had no interest in going into any scientific field. BUT because of my personal experience with serious clinical depression and anxiety disorder during my early years of life, I started to become interested in studying psychology. So I went back to school in my early 30’s to study it. During that time I realised I wasn't interested in becoming a counselor but that I wanted to be in research. I wanted to research the biological aspects of how the brain and the body talk to each other. 

I ended up getting an internship to work with a new Psychiatric Research unit that was set up and worked with Professor Michael Berk. I started to realise that there was nothing in the psychiatry research area that looked at nutrition and what the possible links were between nutrition and mental disorders. At the time there was an area called Psychoneuroimmunology. This looked at how the immune system speaks to the brain and how it is relevant in mental disorders. 

Around the same time, we started getting some interesting data coming out of the USA from neuroscience. It stated that there were at least two areas of the brain where you develop new neurons throughout your life. It wasn’t that you were born with certain neurons and you only lost them.... One of the key areas that this happens is in the Hippocampus. The Hippocampus is very central to:



Mental health

It is one of the key targets of antidepressant medications. If you manipulate diet in animal studies you quickly manipulate the function of the hippocampus. This was another strand of information that suggested that nutrition should be important in mental health and yet there had been very little studies done! I proposed to develop a study looking at the link between the quality of people's diets and the clinical depression and anxiety disorders. Taking into account all of the things that may influence that relationship such as:



-Body Weight

I pressed on even when people were skeptical…I was able to do my PhD on a large study of people who were very representative of the full adult range, wider Australian population. We had quality assessments on these people and I completed 500 assessments on the women! I had to look at the nutritional field and look at the new ways of understanding diet. We used new statistical approaches that allowed us to catch the whole diet and not just bits and pieces of it. For Example: if you are eating a lot of magnesium you are probably eating a lot of folate as well. You need to understand the totality of the diet to understand that and to look at links properly. 

Were Mental Health and Nutrition Linked?

I found the associations that I expected between mental disorders and nutrition when I completed my PhD… This was the first major study that had good methodology. I then could go around the world to many different research groups where they had big epidemiological studies. They had already collected information on diet and mental health but had not put them together. I was able to leverage my publicity on my PhD study to approach those groups and see if we could collaborate and test the hypothesis. 

In a short period of time, I was able to generate the first studies to look at this link between diet quality and common mental disorders in adolescents. We want to take a preventative approach and this is the primary age of onset. There is a clear link even if you take in things like:

Chaotic Family Environment

Family Socioeconomic Status

Early Life Nutrition 

Early life nutrition affects physical health across the lifespan, but is this true for emotional health? We looked at this with 23,000 mother’s and their children in Norway. We looked at mothers diets in pregnancy, children's diets during the first years of life, and looked at a child's emotional regulation over the first few years of life. We found those very clear relationships independent of all of the other factors that we needed to consider. Many more studies came out and there was a consistency with them that the quality of your diet is very clearly related to whether you develop depression in particular. This is important for many reasons:

-Unhealthy diet: Because of the influence of big food and the way our food landscape has changed across the globe, it is now the leading cause of premature death in men and number 2 in women. 

-Mental disorders: depression accounts for the leading societal disability burden. 

Now that we know the two are linked, it gives us a massive new wave of thinking about the problem of mental disorders. In psychology, we have not had any new treatments for depression in decades and we struggle to address it properly. Some people with depression will:

-Respond to Antidepressants

-Respond to Psychotherapy

But many people are left with symptoms or they are not helped at all. We are at the stage now where we have 10 years of observational data. We see that any healthy diet is associated with about ⅓ reduction in the risk of depression! We also published the first study in humans to look at whether diet quality is related to hippocampal volume. We saw very clear relationships and now that is being replicated in larger samples.

The part that was lacking was the intervention study…. because you can say that these two things are very clear and consistently related but that doesn't mean that one causes the other. You need a randomized controlled study to test that. That is challenging in nutrition because you can't blind the group that they are in.

healthy diet and gut health

Smiles Trial Data and Results

We tried to complete the Smiles Trial and realized it was incredibly difficult. We hoped to recruit 180 people with depression and after 3 and a half years we could only recruit about 67 people. There was a lot of skepticism on the medical side so no one was referring their patients to us. There was also a lot of skepticism with people that were suffering from depression. We did manage to do the trial and when it came time to publish the results we were not expecting to see a significant difference between the groups. These were the two groups that we had:

Group 1: Social Support: which we know is helpful for people with depression

Group 2: Dietary Support: with a Dietitian

When we did the analysis we were stunned because we saw a MAJOR difference between those two groups. About 30% of those in the dietary support group went on to have full remission of their depression compared to 8% in the social support group. What was key with the Smiles Trial was a few things:

  1. There was a very clear correlation between the degree of dietary change and the degree of improvements in people's symptoms. The more they improved their diet the better off they were in terms of clinical depression. 
  2. These changes were not explained by changes in body weight. The average BMI was about 30 and that didn't change. It wasn't explained by other changes such as smoking or exercise either.

We also completed two key pieces of economic evaluation:

  1. Testing how expensive our diet was compared to the diet that people were eating before they came into the trial. Our diet was cheaper!
  2. We did a formal economic evaluation with economics and it showed that there was a AUD$3,000 cost saving per year per person by taking this approach to treating depression! This was because they lost less time out of work and saw fewer health professionals, less often. This benefits them in all aspects of their life!

A few months after we published our study, a group in Australia also published results of their study where they did the same thing but did it with a larger sample size. They found similar results to us. It also showed a tight correlation between the degree of dietary change and the degree of improvement and that it was highly cost-effective. This goes along with the many studies that show that exercise and diet are both important for depression strategies. There is also emerging literature around cigarette smoking and having it be a risk factor for physical health, you also get a mental health benefit if you quit! 

Recently, there was a study published about diet, depression, and obesity in the USA and it also showed that it improved depressive symptoms. There have been three studies now that have targeted people with depression with a dietary approach. We also have substantial literature where dietary approaches have been taken to treat other diseases, not people with clinical depression. But they have measured their depression and anxiety as part of the intervention. 

We are now leading a group of people that are setting up international guidelines for lifestyle psychiatry. Lifestyle medicine is a fundamental principle in psychiatry and it should be the foundation. In the clinical guidelines in Australia, it is already written there. There is just a lack of training for health professionals which means that it's not implemented. We are hoping that international guidelines might start to shift policy and practice (this is in the works!)

What Are Some Dietary Strategies That People Could Implement at Home to Improve Their Mental Health?

There are a few basic things you can do including these 7 tips:

  1. Swap Refined (cereal, white bread) >>>> For Whole (oats, barley, brown rice)
  2. Increase the number and diversity of fruits and vegetables that you take in
  3. Increase Fibre
  4. Increase legumes, such as chickpeas.
  5. Use olive oil instead of butter or other seed oils.
  6. Include fish in your diet throughout the week to get your omega fatty acids.
  7. Very importantly, reduce the intake of processed foods!

Both not getting enough of the good stuff (healthy proteins, fats, polyphenols, fibre) and also quite independently reducing your intake of processed foods. They are independently related to mental health outcomes. 

For Example: A young person is eating a lot of fruits and veggies at home then going out and eating a lot of junk food before, during, and after school. That will still be a big problem. On the other hand, there is an older person that isn't going out and eating junk food all the time but they aren't getting enough fruits and vegetables. We aren't sure which is more important than the other but they are both very important. 

Increase the food that we know that is important for gut and brain health and then decreasing the food we know that is damaging to gut and brain health.

Is Sleep or Body Weight A Consideration For Mental Health?

In some of the epidemiological studies that data was available and it didn't seem that sleep or body weight was involved with mental health. We know that obesity puts an increased risk of diabetes & depression and that depression can often lead to obesity. BUT body weight does not seem to explain the diet/mental health association. I would doubt that sleep would play a major role in it either. Sleep is incredibly important and if you don't sleep well your diet is often poorer as well. With both of these put aside, diet seems to be the driving factor in depression.

gut health and mental health

What Is Your General Feeling About The Medical Community Adopting Your Work?

Although an unhealthy diet is the leading cause of early death and men and number 2 in women, medical practitioners get an average of 2 hours of training in nutrition in their schooling which is a major issue. Our analysis that shows that dietary changes improve depression was only published recently so it is too early to see the feedback. We only have a handful of practitioners around the world that practice it. We are developing online training because there is a critical need to get training in place. In 2015 I had some input in the updated clinical guidelines for the treatment of mood disorders put out by the Royal Australian and New Zealand College of Psychiatrists. We created a concept called step zero. This is where a practitioner FIRST goes over the following when a patient with a mood disorder comes in:




Substance Usage

This is rarely done and if it is they do not dig deep. They assume that everyone knows what a healthy diet is so if they answer that they are eating healthy, they believe them. There have been many people that made “healthy eating” really confusing including Big Food. So unless the practitioner really emphasises it and gives people clear guidelines or writes it down on a prescription pad, it doesn't change behaviour. 

We are also working to have a medicare item for dieticians so that people with mental disorders of all types can go to them. We need this help because people with serious mental illnesses have a lifespan that is on average 20 years shorter than the general population. 

That is because of 3 things:

  1. The fundamental problems with metabolism that goes along with those conditions
  2. The impact of the antipsychotic medications, they are a disaster for peoples metabolic health
  3. Their lifestyle behaviors go down the toilet when they are unwell. They don't exercise, take care of themselves, and they smoke more. 

This is why they are sicker and die so much earlier. We need to address their physical health first and foremost to prevent those things from happening. This is because we know from good research that you can support people (even those with very serious mental disorders) to eat well, exercise, and to stop smoking. This is not been done as a standard treatment. People with mental disorders need to be able to access nutritionists at the very first instance. Even looking at depression we know that you are already at much higher risk of cardiovascular disease, obesity, and metabolic problems. We would say it's not just enough to screen people and say “Are you depressed? You are not overweight and your blood sugar is okay so we won't worry about that.” We need to implement this from the first instance to prevent these chronic diseases. Even if you don't do it for your mental health you can do it for your overall health. There is a strong case of having lifestyle medicine and that should be the starting point and you can build on that.

How Do We Instil The Findings of Your Studies to Mothers and Fathers?

Based on the available evidence, we will be able to prevent some cases of mental disorders developing in the first place if children have a healthy diet from the start of life. Putting everything on the individual without talking about food policies is a BIG mistake. Humans operate within an environment and that environment has a massive impact on the choices they make. We know from history that when the food environment is healthy that the population is far better. 

We have the first steps in Australia for politicians to say “yes, we will think about all of the recommendations made by the obesity coalition around the taxation of sugar-sweetened beverages, the limiting of marketing, and limitations of availability.” This has not happened yet but they have said that they will consider it. The influence on big food regarding policy is more massive than the tobacco industry.

If policymakers and individuals understand that a healthy diet is not just important for avoiding cancer or heart disease down the track, then they might pay closer attention to it. If they understand that this is relevant to children's emotional and cognitive health from the start of life, that will add a lot more weight to the push to improve our food environment. And also for individuals and families to pay more attention to the dietary guidelines. 

Food in itself is so addictive. There are so many addictive qualities and to put the responsibility on the individual is unfair. We need wider policy changes to address this issue. Everything is stacked against us from marketing to the production of food. -Kriben Govender

gut health and mental health

With Your Findings Have You Been Able to Implement These Strategies in Your Life and Have You Seen Improvements in Your Anxiety or Depression?

I developed an anxiety disorder, like many children, when I was about 6 (which is the average age of onset of anxiety disorders based on the US data!) By 13 I was suffering from panic attacks without knowing what they were or why. My first episode of major depression was around 14 and by the time I was 19 I had a really severe episode….

I had generally eaten pretty well but I did not exercise. At this time, I was having trouble sleeping so I started exercising to improve my sleep. That was a key change. I started running and I realized I really loved it! It had such an incredible benefit on my sleep and my mental health and I have been pretty well since then. As a bonus, when I was exercising and sleeping better I was also choosing more healthy foods. This is what we see from our data as well. When we help people improve their diet, they start exercising more. It has this effect on the rest of your lifestyle behaviors. I stayed pretty well since my early twenties by:


-Healthy Diet

-Prioritising sleep

Still to this day, I have seen the benefits from this approach.

How Does Your Smiles Trials Relate to Modulation in the Gut Microbiome Which Can Lend Itself To Improve Your Mental Health?

There is an obvious link. We didn't know anything about the gut-brain axis when we were performing the trial so we did not measure it. But here at the Food and Mood Centre, we are running 20 studies and the large majority of those we are measuring the triad of Diet, Gut, and Mental Health. Very fundamentally we now know that the gut and the resident bacteria are very important for both physical and mental health. We also know that diet is probably the most important factor that affects the health of your gut. We also know from a few studies that you can change the composition and health of your gut within a very short time frame. This was shown by looking at the level of inflammatory markers that are linked to bowel cancer. There were two key studies:

  1. They took 10 people and put half of them on a meat and animal food heavy diet and the other group had a diet that was high in vegetables and fibre. This showed a very rapid change in their microbiome. There were improvements with those that were on the plant-based diet with more short-chain fatty acids. 
  2. They looked at African Americans and South Africans and they showed differences in the health of their microbiome, their diet, and they swapped their diets for two weeks. This showed that their gut health, including the inflammatory markers, went right up in the South Africans and down in the African Americans. 

We know you can change your microbiome and the health of your gut very quickly by changing your diet. There is not a “one size fits all” diet forbear your gut. We know that your gut needs fibre, a diversity of that fibre, polyphenols, fats (especially those from fish, olive oil, and nuts) and it doesn’t love saturated fat. We need to get focused on whole foods, fermented foods, and diversity in our diet. Michael Pollan got it right when he said “eat real food, not too much, mostly plants” Try and get the fibre into every meal that you have. If you need the extra fibre boost you can supplement with any of these products!

diet and mental health

Is There A Clear Mechanism of How The Short Chain Fatty Acids and Polyphenols Work?

The primary activity of your gut microbiota is to break down dietary fibre that our human enzymes cannot break down. When you eat fruits, vegetables, and legumes, they make their way down into the gut. The bacteria then ferments them to break them down. That fermentation process produces all of these metabolites and molecules. They help the body in many ways including modulating our immune system, both within the gut and in our entire body! They interact with every cell in the body via G-Protein coupled receptors. These receptors influence how genes behave and what things are turned on and off. The data from animal studies suggest that they also influence the integrity of the blood-brain barrier. They are important in:


-Brain Plasticity


If you don't have enough dietary fibre they cannot do any of those things. This is the issue we are having in the west because we aren't eating near enough fibre or enough diversity of dietary fibre. Our gut diversity is a marker of good gut health and it has been drastically going down. We are seeing a decrease in the microbes that we used to have when we were living a traditional lifestyle….Based on the evidence this may put us in jeopardy especially if nasty new viruses come along. OR if you encounter a new food source where you have to make a rapid change to your diet to survive. Having this diversity of microbes makes it much more likely that we are going to adapt! Diet is the quickest and most foolproof way in making an improvement very quickly.

What Is The Deal with Neurotransmitters?

When microbes ferment dietary fibre they produce neurotransmitters AND they also change their environment so your body's own production of neurotransmitters has changed as well. We do know that the bacteria in the gut influence the metabolism of tryptophan. Tryptophan is a precursor of serotonin so by doing that you will influence the levels of serotonin in the brain.

Next, we have Gabba and it is an anti-anxiety neurotransmitter. When you have a fermented product such as Kefir, you are consuming Gabba because the bacteria produce the neurotransmitters and that is what ends up in your food! Many people think that they should be having fermented products because of the live bacteria that are in them but many fermented products don't have live bacteria. This is because the bacteria has eaten the substrate and they die off because there isn't any food. BUT this doesn't matter because what you have in the product is all the metabolites that have been produced in the fermentation process and you also have dead bacteria that have a lot of bioactive properties as well. Make sure to start eating beans every day. They are great for your gut microbiome. ALSO Consume fermented foods regularly. You can buy this kit here to help you get started!

Milk Kefir is the one thing that turned everything around for me regarding my anxiety and depression struggles. There are tons of metabolites that are produced by the fermentation of milk kefir that can have a huge benefit on your health -Kriben Govender

If you want to learn more about this fascinating information you can find Felice’s book here, Brain Changer. There are many things that you can do for your gut health that can also benefit your mental health as well! Every part of the human body is interwoven and connected. Remember to eat your fermented foods and enjoy a healthy diet (including fish, legumes, nuts, olive oil and a variety of fibre from plant foods!), exercise as much as you can, and reap the mental health benefits as well as the physical ones. Share this with a friend or family member that would benefit from this information!

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