How the Mediterranean diet benefits mental health

Counselling and medication gain most of the treatment attention for depression, but the promise of dietary changes to help to improve the outlook of people with depression and other common conditions such as anxiety is gaining traction. Welcome to the rapidly moving world of nutritional psychiatry which is uncovering key links between diet and mental health. And one such dietary pattern, the Mediterranean diet, is now building a research base behind it to support a change to the dietary themes this diet promotes to help improve mental health. And that’s what I’ll be exploring more about in this podcast episode.

Links referred to in the podcast

SMILES trial https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0791-y
Effect of a Mediterranean diet with fish oil on depression https://pubmed.ncbi.nlm.nih.gov/29215971
Effect of a Mediterranean diet on depression in young men https://pubmed.ncbi.nlm.nih.gov/35441666

Episode transcript
To access the full episode transcript, go to the following link and select the individual podcast episode and then click on the ‘Transcript’ tab https://thinkingnutrition.buzzsprout.com

Connect with me
Instagram: doctimcrowe
Facebook: Thinking Nutrition
Twitter: CroweTim

When it comes to your mental health, what you eat can have a profound impact on your mood and how you feel. A nutritious diet isn't just good for your body. It's good for your brain too with a growing body of research now showing that diet can be just as important to mental health as it is to physical health. In just a decade, the rapidly growing knowledge in this field has given rise to a new concept called “nutritional psychiatry” where before it was barely a blip on the health care radar.

How food and mood are related is a two-way street. What you eat can affect your mood, but your mood also influences what you choose to eat. You’re more likely to make positive food choices when you’re in a good headspace.

First, let’s get some background in place here. A role for nutrition in mental health comes from the long-known association that a healthy diet is a common factor linked to a positive mental outlook. The problem with most of the observational research in this field though is that it is hard to tease out which one comes first. Are people who are experiencing depression or anxiety more likely to eat poorly because of their mood? Or does a poor diet worsen symptoms of depression and anxiety?

And this is where the evidence is now growing via actual intervention trials to show that diet can have a direct impact on mental health. But in this podcast episode, I want to profile one particular type of dietary change, that being the Mediterranean diet, and how it can influence mental health by profiling evidence from several clinical trials.

About the Mediterranean diet

The Mediterranean diet has long been considered a benchmark for a model of a healthy diet. It is also recognised by the World Health Organization as a healthy and sustainable dietary pattern. There is no one best way to eat for everybody, but a person can look to the Mediterranean diet as a guide to help make positive choices for eating healthier.

Interest in the health benefits of the Mediterranean diet began to grow in the 1960s. Arising from the observation that people in this region were healthier and had a lower risk of many chronic conditions.

The traditional Mediterranean diet originated in the olive-growing areas of the Mediterranean region. It has a strong cultural association with these areas. Although the term ‘Mediterranean diet’ is commonly used, it is more a dietary pattern or dietary theme rather than a single fixed diet. That’s because the types of traditional foods featured in it can vary based on geography in the Mediterranean region.

The Mediterranean diet is not just about the foods eaten. There are also social and cultural factors as part of it such as eating with friends and family, post-meal siestas and lengthy meal times. These habits promote positive social connections and a less stressful outlook on life.

The themes of a Mediterranean dietary pattern can be summed up as:

daily consumption of vegetables, fruits, wholegrains and legumes
including healthy fats such as olive oil and nuts daily
fish and seafood eaten at least twice per week
a moderate amount of eggs, poultry and dairy products
while red meat is eaten at most twice per week.

The Mediterranean diet is one of the most well-researched diets. And almost all this research points in a positive direction for favourable health benefits.

Intervention trials

So with that out of the way, what does the research have to say about eating around a Mediterranean dietary pattern theme and mental health? In what I consider the most important nutritional intervention study ever conducted in the area of mental health for the quality of the research itself and the implications of the results, a clear link has been established between diet changes that centred around the themes of Mediterranean dietary pattern and improved mental health.

Called the SMILES study (which stands for Supporting the Modification of Lifestyle in Lowered Emotional States), this was an Australian study led by Professor Felice Jacka from the Food and Mood Centre at Deakin University. And it used the most powerful type of study design: a randomised controlled trial. And I’ll link to the study in the show notes https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-017-0791-y

Sixty-seven people with moderate to severe depression were involved in the 12-week trial. Those in the treatment group received seven 60-minute sessions of dietary counselling. The control group received a matching social support protocol but got no specific dietary advice. Almost all the participants were receiving another active treatment for their depression be it psychotherapy, medications, or both.

The dietary counselling sessions were about getting people to eat more in line with dietary advice aligned with a modified form of the Australian Dietary Guidelines and Dietary Guidelines for Adults in Greece. So, there was a distinctly Mediterranean flavour to the advice. Wholegrains, fruits, vegetables, nuts, legumes, lean meats, chicken, and seafood were on the menu and highly refined starches, sugar and highly processed foods were shunned.

After 12 weeks, there was a statistically and clinically significant improvement in the rating scale of depression in favour of the dietary treatment group. With almost a third of people in the dietary intervention achieving what was considered clinical remission from their depression. This was compared to just 8% who achieved this in the control group.

A range of secondary scores looking at mood and well-being were all pointing in a positive direction as well. Improvement in depression scores was also related to the degree of adherence to dietary advice. And the benefit of diet on depression was independent of any changes in body weight, self-efficacy, smoking rates or physical activity.

A strength of the study was including a control group that received an equal level of social support from the research team. This is important as social interaction by itself can improve depression outlook and this could have been an influence on those receiving dietary advice from the research team.

The study was small in size, but the compliance and completion rates were very good. The fact that the dietary intervention group could make significant improvements to their diet quality suggests that dietary improvement is achievable for those with clinical depression despite the fatigue and lack of motivation that are prominent symptoms of this disorder. And more so, a larger study published in 2019 that included 152 adults with self-reported depression also saw a clinically significant improvement in depression scores after following a Mediterranean-style diet supplemented with fish oil for 3 months. And I’ll link to this study in the show notes. https://pubmed.ncbi.nlm.nih.gov/29215971

But these initial studies don't stand alone as far use a Mediterranean-style diet to improve mental health. Published in April of this year, Australian researchers looked at how it can improve the outlook of depression in young men. Depression is a common mental health condition which affects 1 in 8 males each year, with younger adults over-represented. Making positive diet changes in young adulthood has the potential for not only improving health but also carrying over those dietary changes to later in life. Especially when you consider the poor diet quality of younger men with depression in general.

The study was a 3-month randomised-controlled trial that assessed the effect of a Mediterranean dietary intervention in the treatment of diagnosed moderate to severe depression in young men aged 18 to 25 years. 72 men completed the study. And similar to the SMILES study that I just described; the control group also took part in a social support group, but didn’t receive dietary advice. Adherence to the Mediterranean diet, degree of depression and quality of life were all assessed throughout the study using validated tools. And I’ll link to the study in the show notes. https://pubmed.ncbi.nlm.nih.gov/35441666

And the results were very positive with both depression and quality of life showing a greater positive change in line with following a Mediterranean-style diet. In fact, every one of the 36 people in the dietary intervention group saw an improvement in their symptoms of depression, with 36 percent reporting a depression score that indicated low or minimal depression. Remember that all men in the study started with a depression rating in the moderate to severe range. But in the 36 men in the control group that just only received the befriending social support, none of the participants had an improvement in depression scores that got them down into a low or minimal range by the end of the study.

How the Mediterranean diet works for mental health

Okay, so the big question: how could a Mediterranean diet be working here? If you said, healthier eating, then yes, that’s certainly the key theme without a doubt. And it could be mostly the effect of replacing a diet higher in highly processed unhealthy foods which more healthy foods. You don’t need a degree in nutrition science to know that that will likely be of benefit to anyone’s health.

But digging deeper, several more possibilities are likely. It could be related to a direct effect of improved nutrition providing more nutrients to the body. Equally, an anti-inflammatory effect of the diet could also be at play. And intriguingly, it could also be from a well-fed and more diverse gut microbiota. The gut has a two-way communication link with the central nervous system – and we call this the gut-brain axis. A Mediterranean-style diet could benefit depression because it causes gut bacteria to make more or less of certain compounds that alter brain chemistry. One of these chemicals is called butyrate which is a short-chain fatty acid that has been shown in animal studies to have antidepressant effects, possibly by altering levels of serotonin and other neurotransmitters in the brain.

While this podcast had the Mediterranean diet as its focus, I want to state clearly that the Mediterranean diet is not the best diet. I’ll let you absorb that bit of nutritional dogma heresy for a moment. It is only the best-researched diet. There are likely countless dietary patterns that could offer benefits in line with this healthy eating pattern. A Japanese-style diet to name just one. And it is culturally just not appropriate to impose one type of culturally developed diet on someone deeply ingrained with a completely different dietary pattern from another culture.

Instead, play to the themes of eating a wide variety of nutritious minimally processed whole foods from all food groups and where plant foods are very much in focus. This sort of diet would naturally contain different types of fibre and beneficial gut health nutrients. And from that, you can expect to reap not just the physical health benefits, but also mental health benefits.

So, let’s wrap all this up. Diet and mental health is a rapidly growing research field. We can expect more research to come to light linking the benefits of healthy eating patterns with improved mental health. But really, the sorts of diets being studied for improving mental health are not that much different to what broad dietary guidelines have promoted for decades. You know, those guidelines that only a small fraction of the population follows yet seem to be continually blamed for our health problems? Now that’s mental.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

If you find this podcast of value, then please consider sharing it with your friends and colleagues. Or maybe even leave a review. This all helps increase the ranking and reach of the podcast which means a big win for credible evidence-based nutrition messages while helping to dilute out the crazy and making the world a slightly less confusing place.

I’m Tim Crowe and you’ve been listening to Thinking Nutrition.

Thinking Nutrition

How the Mediterranean diet benefits mental health

Listen to this podcast on