By Gina Pegram 

The idea that the health benefits of what we eat extend beyond our physical health to influence our mental wellbeing is gaining traction in mainstream media. “Mood-boosting” is now up there with “superfoods” as a buzzword to describe ingredients & recipes.

A national newspaper even touted the “happiness diet” as the ultimate solution to the January blues, all neatly packaged in a 2-week meal plan (1). So yet again we witness the diet industry’s ability to make a fad diet plan out of concepts grounded in genuine science. I’ll come back to this later, but first let’s discuss the research that has led to this buzz…


So where has this notion come from?

Research is mounting to support the idea of the gut as the “second brain”; that what is going on in the gastrointestinal tract has the power to influence our mental health, and vice versa. ‘Gut Health’ has become quite a trendy term, in particular highlighting the importance of the gut-brain axis (the connection between the digestive and central nervous systems).  But this isn’t a new concept.

In fact, thousands of years ago the ancient Greek physician and ‘father of medicine’ Hippocrates professed that “All diseases begin in the gut”, whilst back in the 18th Century the French Psychiatrist Phillipe Pinel concluded “The primary seat of insanity generally is in the region of the stomach and intestines”. It is only more recently, with leading-edge research into the gut microbiome (the colony of trillions of bacteria residing in our digestive tract), that we have started to build an evidence base that supports this theory. Whether it is the ‘primary seat’ is debateable, but it certainly has an intriguing role…


What foods are involved in this gut-brain connection?

It is well established that low levels of the neurotransmitter Serotonin are associated with feelings of depression. With 90% of serotonin receptors located in the gut (2), it’s no surprise that foods that help to “boost” this neurotransmitter are considered to play a role in the food-mood relationship. Such foods include those rich in tryptophan, an amino acid that aids in serotonin production (3), abundant in foods like poultry, oily fish, beans and lentils.

And what about the fish that my granny always used to feed me up with before tests and exams? It is an age-old understanding that certain fats are important ‘brain food’, but we are seeing omega-3 implicated more and more as a nutrient of interest in the prevention of mood disorders too (4). When it comes to the microbiome and what we feed all those trillions of gut bugs, diversity is key. They love a variety of prebiotic foods like fibrous fruits & veg, and wholegrains (5). And to get even more of the good guys in there we can also increase our consumption of probiotic foods which actually contain these bacteria – things like kefir, yoghurt, sauerkraut, and kimchi. Interest in the gut microbiome and its potential influence on mental health is continuing to grow at an exciting rate, but so far we have decent evidence to suggest that consumption of these “gut-friendly” foods is associated with fewer symptoms of depression (6).

In recent years this area, now commonly referred to as ‘Nutritional Psychiatry’, has been burgeoning. However, the supporting research has largely been on healthy populations, or observational in nature. The fundamental limitation of these kinds of studies is that we cannot deduce the direction of the link (poor diet to depression), as it is quite possible that somebody with depressive symptoms will alter their diet. What the field had been waiting for was the gold standard in epidemiological research – a randomised control trial (RCT) in clinical populations…


Cue the SMILES trial.

Fast-forward to 2017 and we have the first published RCT, born out of the Food & Mood centre at Deakin university, Australia (7). Across a 3-month period, patients with depression who ate a ‘poor quality’ diet were assigned to either a “food” dietary intervention group or a “social support” control group, alongside their standard clinical treatment. Those in the “food” group were supported by a dietician to make dietary modifications in line with the “Mediterranean diet” (to eat more wholegrains, fruit & veg, beans, legumes, fish and lean meats, eggs, nuts & olive oil), a well-researched dietary pattern that appears to be favourable for overall health (8). Those in the “social support” group attended friendly meet-ups (non-therapy related), established as beneficial in depression treatment.

The results were pretty astounding: at the end of the 3-month period, those in the dietary intervention group were 4x more likely than those in the social support group to have achieved criteria for remission (32% vs 8%), and had reduced symptoms of anxiety as well as depression. It should be noted too that the greatest improvements were seen amongst those who adhered closest to the Mediterranean diet plan provided.

This is about as solid as it gets in terms of the evidence to date supporting the link between food & mental health outcomes. But this is in clinical populations, so how does this relate to us? Well that leads me back to why I became so interested in the subject in the first place…


Why is all of this relevant and worthy of attention?

5 years ago, whilst visiting the ward that my mum spent several months at for treatment of severe mental illness, I couldn’t help but notice the shockingly poor quality of the food being served. Witnessing my mum, a previous foodie, shunning the canteen meals in favour of packets of biscuits in the confinement of her room got me thinking about the impact that improved meals could have on the outcomes of in-patient care. What the SMILES trial demonstrates is that it is not necessarily depression that is causing poor dietary choices, but it clearly indicates that what we eat has the potential to exacerbate or reduce symptoms. If this is the case, then couldn’t a focus on improving food possibly reduce time spent in care, essentially costing the health sector less in the long-term? A follow-up economic evaluation of the SMILES trial found that those undertaking the dietary intervention cost the health sector over $3000 less than those in the social support group. I really think this could be an important avenue for future research and healthcare policy, and should not be underestimated.


But there is always a “but”….

Although this area of research is worthy of the buzz based on how valuable it could be for certain people, we need to make sure we don’t get ahead of ourselves. Like everything in nutrition, it isn’t black & white, and important nuances must be noted…

First, I am by no means suggesting that diet is a ‘cure’ for depression. Mood disorders are complex mental illnesses, with multiple component causes which may be biological, neurochemical, psychological and/or environmental. To suggest one simple cause/treatment is not only wholly reductionist but also extremely uninformed. If someone were to tell my family (as, worryingly, some “doctors” are suggesting online) that my mum could be ‘cured’ by merely eating more fruit & veg and less processed foods, I wouldn’t have known whether to laugh or scream.

It is not a case of “plates over pills”. Years of in- and out-patient care, several rounds of electro-convulsive therapy, and likely lifelong medication have been responsible for her improvements. Without these treatments, she would not be where she is today.

However, what I can say is that, in the latter stages of her recovery, food has played a significant role. Over the past couple of years, we have included more of the foods associated with improved wellbeing, and have observed some benefits, independent of her standard meds. For example, it feels as if the dietary changes have counteracted the “sleepy” side effects of the medication, giving her more energy throughout the day, and healthier sleeping patterns.

It is interesting that, as well as aiding in serotonin production, tryptophan can also be converted to melatonin. Melatonin is the hormone that helps to regulate your sleep cycle, and which is largely disturbed in depression. Although we can’t say that her improvement is a result of the independent effect of tryptophan contained in foods, it seems clear that we can attribute it to overall improved diet.


Secondly, it’s important that we recognise the behavioural effects that may play a role in this, over and above specific nutrients. What seems to be more striking in my mum’s recovery is the benefit of actually cooking & eating together, encouraging the social connection that food brings. This is something massively lacking in hospitals when the food doesn’t even attempt to entice patients away from their rooms.

As mentioned, depression is a multi-faceted mental illness. A key symptom of depression is social isolation, and this is why social support has long been part of the treatment plan. Encouraging patients to eat together (partly by providing good food!) could be equally powerful. This is where I think the Med diet seems to be consistently coming out on top in observational studies of mental health (9). Not only do the foods themselves have properties linked to improved mood & reduced anxiety, but generally the groups observed follow a dietary pattern that gives precedence to family gathering and sharing at mealtimes, something we seem to have lost in comparison here in the UK.



Finally, I want to emphasise that although referred to as the Mediterranean “diet”, it is a dietary pattern of inclusion. There are no single demon foods, just as there are no single wonder foods (though “healthy” fats and wholegrains are championed). Really, it is just pointing towards what we know already, right? That a balanced diet including all foods (& alcohol) in moderation, is the best diet for overall health, including mental health. Having a chocolate bar isn’t going to give you anxiety, just like eating a fillet of salmon won’t cure depression.

In fact, restricting said chocolate bar may increase anxiety around food, and over time this can lead to isolation and poorer mental health. As mentioned earlier, diversity is essential for the good bacteria in your gut to thrive, and recent research suggests that they may in turn influence mental health. How do we increase diversity? We include ALL foods. Granted, some foods in larger amounts than others, but diversity isn’t cultivated by exclusion. I can say from experience of cycling between different food group restrictions (some medically enforced, some not) that this wreaked havoc on my gut. Now I’m better informed, I can see how this may have contributed towards my anxiety, which in turn manifested itself in the gut (and so the vicious cycle continued…).

The gut-brain axis & stress is a whole other topic of its own, but for the purposes of this article I just want to emphasise that restricting foods can actually do more harm to our health (physiologically, biochemically and psychologically) than just eating that supposedly ‘bad’ food. This is where the ‘happiness diet’ nonsense that I drew upon at the start is so problematic. In fact, the subjects in the SMILES trial were encouraged to eat according to appetite rather than intentionally limit intake, not viewing it as a diet at all related to weight. Slightly different to the promotion of the ‘happiness diet’ to help you “smile yourself slim” (…face palm).

So, bottom line

Good nutrition can be an important part of our mental wellbeing toolbox, and it is common sense that we often feel rubbish if we haven’t eaten any veg all day. In clinical settings, improvements in diet, though not a cure, may be an effective adjunct to conventional medicine. This could improve treatment outcomes while potentially being more economically viable in the long-term. In general, though, focusing on the minutiae of the moral value of food as it relates to our mood, while ignoring our desires and intuition, is likely to do more harm than good. Okay, maybe living solely on high-sugar, processed & fried foods wouldn’t make me the best version of Gina to be around. But, having permission to eat these foods when I fancy? That makes me happy. They might not feed my good gut bacteria, but they feed my soul. And that’s a part of me that can’t be measured by a blood sample.


A little bit about Gina

I’m a Nutrition & Behaviour MSc student at Bournemouth Uni, focusing on the field of Nutritional Psychiatry. I’m currently investigating the links between diet and mental health, working closely with clinical research centres and mental health charities in Oxford. During my Psychology degree at Cardiff Uni, I became fascinated by how our psychology and the food that we eat are so interconnected. From this, I chose to complete my research project on the cognitive modelling of Orthorexia. I then went on to work in consumer & sensory research for food brands, while completing diplomas in Eating Psychology and Food Science, which led me to my current MSc. 
When I’m not studying or researching, I’m creating recipes for events & organisations. I currently volunteer at a community kitchen 1-2 days a week. Whilst there, I help to teach cooking skills to vulnerable people of all ages, including low-income families, marginalised groups, and those with mental illness, cognitive disability, and recovering from addiction. I’ve seen in practice the way that food & cooking has had an impact on these groups and on my family through recovery from mental illness, and this is what ignites my passion for this research area. Gina’s Happy Kitchen (the name now given to my recipe development business) was born out of this interest in psychological well-being and cooking, the science of food and mental health, as well as in finally finding happiness and peace with food. 



  • Yano, J.M., Yu, K., Donaldson, G.P., Shastri, G.G., Ann, P., Ma, L., Nagler, C.R., Ismagilov, R.F., Mazmanian, S.K. and Hsiao, E.Y., 2015. Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell, 161(2), pp.264-276.
  • Jenkins, T., Nguyen, J., Polglaze, K. and Bertrand, P., 2016. Influence of tryptophan and serotonin on mood and cognition with a possible role of the gut-brain axis. Nutrients, 8(1), p.56.
  • Su, K.P., Matsuoka, Y. and Pae, C.U., 2015. Omega-3 polyunsaturated fatty acids in prevention of mood and anxiety disorders.Clinical Psychopharmacology and Neuroscience, 13(2), p.129.
  • David, L.A., Maurice, C.F., Carmody, R.N., Gootenberg, D.B., Button, J.E., Wolfe, B.E., Ling, A.V., Devlin, A.S., Varma, Y., Fischbach, M.A. and Biddinger, S.B., 2014. Diet rapidly and reproducibly alters the human gut microbiome. Nature, 505(7484), p.559.
  • Dash, S., Clarke, G., Berk, M. and Jacka, F.N., 2015. The gut microbiome and diet in psychiatry: focus on depression.Current opinion in psychiatry, 28(1), pp.1-6.
  • Jacka, F.N., O’Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., Mohebbi, M., Castle, D., Dash, S., Mihalopoulos, C., Chatterton, M.L. and Brazionis, L., 2017. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’trial).BMC medicine, 15(1), p.23.
  • Trichopoulou, A., Martínez-González, M.A., Tong, T.Y., Forouhi, N.G., Khandelwal, S., Prabhakaran, D., Mozaffarian, D. and de Lorgeril, M., 2014. Definitions and potential health benefits of the Mediterranean diet: views from experts around the world. BMC medicine, 12(1), p.112.
  • Lassale, C., Batty, G.D., Baghdadli, A., Jacka, F., Sánchez-Villegas, A., Kivimäki, M. and Akbaraly, T., 2018. Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies.Molecular psychiatry, p.1.




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