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In this guest blog post, Dr Megan Rossi, an award-winning gut health scientist, dietitian and founder of The Gut Health Doctor explores the science behind a diet and how it can affect our mental health.
You may have thought about the links between diet and your immune health, energy levels and muscle recovery - but how much have you considered the impact of food on your mood?
Perhaps you have noticed that you feel a little lower after weeks of a busy project, eating lots of convenience foods, or even after just a weekend binge at a festival - but have you wondered why?
Thanks to the latest science, we now know that a poor diet can influence the risk of low mood and depression - and that improving your diet can help improve your mental health too.
Proof is in the pudding
The SMILES trial was a landmark study in Australia that showed us the power of food to help support mental health. In this trial, people with depression who had a poor diet (high in ultra processed foods) were put on either a modified Mediterranean diet or had befriending counselling. All remained on their usual medication, such as antidepressants.
So what exactly is the Mediterranean diet? It involves lots of vegetables, fruit, nuts and seeds, legumes, wholegrains, cereals, healthy fats like extra virgin olive oil, fermented dairy like natural yoghurt and fish. As a result, it's high in fibre (around 50g a day), so your gut bacteria are getting lots of the diverse dietary fibres they need to perform their best. More on that here.
In the 'SMILES' trial, the improvements reported in the mental health of those eating a Mediterranean diet were impressive. After 12 weeks, over 30% had a major improvement in their diagnosed depression, compared with just 8% in the therapy group.
What this study shows is that tackling your diet can be a highly effective, and empowering way to improve your mental health. Now it's important to reinforce that no one with depression should ever abandon their medication for a new eating plan, but rather as an additional therapy, or in the early stages if you start to experience low mood, focusing on your nutrition can lead to profound improvements, and certainly this is what I have witnessed in my own clinic with clients too.
So how is it possible for your diet to have such an immense impact on your mental health? Our gut and brain communicate with one another, which you may have heard referred to as 'the gut-brain axis'.
New science has shown the amazing ways in which your diet can affect your brain and emotions:
It has been scientifically proven that what you eat is linked to the size of parts of your brain involved in memory and emotions
A healthy diet can encourage the growth of the hippocampus, which is involved in regulating emotions and memory. This was illustrated in an 11-year study published in 2018. Participants who had a typical Western diet (high in processed food and red meat) had a smaller hippocampus on average than those who had a healthier, plant-rich diet.
Anyone familiar with my work knows that I'm all about looking after your microbes. We have trillions of them, including bacteria, and they're responsible for and involved in thousands of functions, such as mood regulation. So how can the food you eat change the way you feel? Plant foods, like veg, fruit, wholegrains etc. feed and nourish our gut bacteria who in turn communicate with other organs including our brain. These little guys can only do their job properly if they're fed in the right way, and each type of bacteria likes to feast on different types of plants.
People with depression have been shown to have a less diverse range of gut microbes. Interestingly, when researchers transferred gut bacteria from people with depression and put them into rodents, the animals started to display signs of depression - and according to a review of 21 studies published in BMC Psychiatry last year, giving anxious and depressed rodents a transplant of a healthy community of microbes can reduce these symptoms. Now, although this is very exciting, these therapies are still yet to be proven in human studies, so for now it's best to stick with diet as a means to support your mental health.
To sum up, a diet rich in diversity (aiming for 30 plant points a week) has been shown to help boost and support your mental health, as well as bring a whole host of other benefits! So let's take a look at how we can include the magic of the Med in our diet.
It's pretty grey in the UK right now, and while I'm sure we'd all love a trip to Italy, what's probably more realistic is looking at how you can bring the Mediterranean way of eating to your home.
Extra virgin olive oil: When it comes to choosing which oils to use in your cooking, in terms of research into health benefits this is hands down the winning oil. I even replace butter with this in most of my cooking to get the extra health benefits. That being said, if you love the flavour of butter, rest assured it's about INclusion not EXclusion, so butter can still absolutely be on the menu.
Oily fish (sardines, salmon, mackerel): include two portions of omega-3-rich oily fish a week ensures good communication between brain cells (research has even found that people with depression tend to have lower levels of omega 3 in their blood). If you don't eat fish or are concerned about the environmental aspects, then it might be worth considering an algae oil supplement to make sure you're getting enough omega-3.
Herbs and spices (basil, oregano, turmeric): not only a great way to add flavour to every dish, and help reduce the need for salt, these also have health benefits - for example there is an active component in turmeric that has been shown to help reduce cortisol, the stress hormone.
Fermented dairy: Swap standard dairy for fermented varieties, such as live yoghurt, kefir and 'aged' (i.e. not mass-produced) cheese, such as Parmesan.
Wholegrain experimentation: If your go-to to is rice (even brown) try to swap for pearl barley, barley, rye or oats - doing so will not only help to nourish a wider range of beneficial gut bacteria, but they're likely to keep you fuller and more satisfied for longer.
Legumes: Eat plenty of legumes such as chickpeas and lentils. These are rich in prebiotics and fuel anti-inflammatory gut bacteria. The tinned versions are my go-to for convenience - just triple rinse with water if you struggle with their wind effect!
Tea: People who drink three or more cups daily have been shown to have lower rates of depression. Tea is rich in a range of plant chemicals such as L-theanine, which has been linked with lower levels of cortisol. I recommend switching to decaf or a herbal tea after lunch, to ensure your sleep isn't disturbed by the caffeine.
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For any other geeks like myself, here is the published science behind the SMILES trial.