Mental Health Awareness Week starts on the 23rd of September, so I think it's timely to look at how much impact our diet can have on our mood.
We know poor diet has a big impact on our physical health – globally it's responsible for more deaths than any other risk factor, including smoking. Just the top three dietary factors combined (not eating enough wholegrains, not eating enough fruit, and eating too much sodium) are estimated to account for around half of all deaths attributable to diet. But what about our mental health? How much impact does what we eat have on our risk of developing anxiety or depression?
Before we get into that, how about a quick overview of the impact our mental health has on our quality of life…
Back in 1990, the World Bank commissioned a huge project, called the Global Burden of Disease study. This study was designed to measure the causes of disability and death all around the world. It was a massive undertaking, but crucial to inform health policy and better target public health spending. What it also did was shed light on the impact of certain hitherto neglected health issues, particularly mental illness. Since the original study, the WHO has taken over the work of updating the findings, with the next major update undertaken in 2010.
The data gathered during these studies has been analysed by hundreds of researchers over the years, and they have been able to take a closer look at specific areas of interest.
In 2015, researchers focussed on the impact of mental, neurological and substance abuse disorders on our health.
Mental disorders are characterised by abnormal thoughts, emotions or behaviours, and include conditions such as depression, schizophrenia, and anxiety disorders.
Neurological disorders are diseases of the nervous system, and include conditions like epilepsy, Parkinson’s disease and Alzheimer’s disease.
Substance abuse disorders result from the harmful use of psychoactive substances, like drugs and alcohol.
They found that while such disorders accounted for around 2.3% of early deaths worldwide, they accounted for a staggering 28.5% of all years lived with a disability. Simply put, we are living longer but we are living with more disabilities, and an increasing number of these disabilities are due to issues with our psychological health.
Out of mental, neurological and substance abuse disorders, mental disorders were the biggest contributor to the years lived with disability, with depression and anxiety accounting for almost 60% of all mental disorders.
Now back to our original question - what kind of impact does our diet have on our risk of developing anxiety or depression?
To be fair, this could be a bit of “the chicken or the egg” situation, couldn’t it? Is your diet impacting your mood, or is your mood dictating the kinds of foods you feel like eating?
What’s the current evidence saying?
Rather than focussing on single nutrients (which research has in the past, as this is really the only way of isolating a specific nutrient to study), research around diet and mental health is starting to pay particular attention to dietary patterns that support good mental health - the "big picture" stuff. Now I reckon this is great news, because on the one hand it steers us away from thinking that popping a supplement might be the best approach; and on the other hand it allows room for quite a bit of freedom in the way we eat, within some broad guidelines.
There is no “one perfect way to eat”, no “one diet to rule them all”. Rather, there are many healthy ways to eat found all around the world and incorporating many different cuisines, all sharing some important features: higher intakes of wholegrains, fruit and veg, legumes, nuts, fish; and lower intakes of highly processed foods. It’s also a much better approach to eat whole foods than try and rely on various supplements, as you’ll get a range of other beneficial compounds from whole foods, in addition to the specific nutrient or nutrients you are after.
Studies have shown strong associations between diet quality (measured by the factors I listed above) and prevalence of mental health issues, especially depression and anxiety. A study in 2010 of over 1000 women in Australia compared a Western diet (one high in processed foods, refined grains, sugary products and beer), with more traditional diets (based on vegetables, fruit, wholegrains, meat and fish), and looked at the incidence of depression and anxiety. The researchers found traditional diets were associated with a lower likelihood of anxiety and depression. Interestingly, this association was still seen after adjustment for other factors affecting mental health, such as age, socio-economic situation, physical activity and education level. However, this study couldn’t entirely rule out mental health issues being the cause of poor diet (that "chicken or the egg" thing again), but it certainly demonstrated a strong association even when other possible contributing factors were taken into account.
Another study, this time in 2011 with more than 3000 Australian teenaged participants, found not only a strong association between diet quality and mental health, but a clear pattern of improvement in mental health with dietary improvement, and decline in mental health with a decline in dietary quality, at the two-year follow-up. The results of this study were also adjusted for other factors often seen to affect mental health status, including socio-economic situation, gender, dieting behaviours, physical activity and body weight. The authors of this study noted the importance of diet quality during the teenage years, as the majority of mental health issues develop during this period. But what I found most interesting about this study was that it was able to state that the data it found did not support the theory that poorer mental health lead to poorer dietary choices, lending weight to the poorer diet leads to poorer mental health outcomes argument - potentially answering the "chicken or the egg" question.
OK, so the research is showing a pretty strong association between what we eat and our mental health. It also looks like it may have answered the "chicken or the egg" question; that is, poorer eating habits lead to poorer mental health, rather than poorer eating habits as a consequence of poor mental health.
So how is this even happening? How is what we’re eating affecting our mood?
According to a brilliant webinar I watched recently by Dr Tetyana Rocks from the Deakin Food and Mood Centre, there are four possible ways in which the nutrients we eat could be exerting their influence on our brains:
1. Improving brain plasticity: this refers to the brain’s ability to adapt, change and recover over time. A healthier diet supports brain plasticity (also called neuroplasticity) by supplying a variety of nutrients that support the health of the brain in general, and therefore its ability to protect itself from cellular damage. These nutrients can even slow the rate of brain shrinkage with age!
2. Protecting against oxidative stress: a healthier diet contains more antioxidants, which protect against cell damage in the body, and research has shown that total antioxidant levels are higher in individuals without depression.
3. Fighting inflammation: a strong association has been observed between inflammation and depression, with the risk of developing a depressive disorder increasing as inflammation levels in the body increase (inflammation is usually measured by a marker in your blood called C-reactive protein, or CRP). In a 2010 study of nearly 1500 Australian women, researchers observed a 44% increase in the risk of developing a major depressive disorder for every standard deviation increase in C-reactive protein levels. There are many nutrients in a healthy diet that flight inflammation in the body.
4. The gut-brain axis: what?? Yes, there is a growing body of evidence showing communication between the gut and the brain, in both directions! Gives new meaning to trusting your gut, or having a gut feeling, doesn't it? Supporting your gut health by giving your gut bugs a constant supply of food (dietary fibre) helps you maintain a thriving and diverse population of these critters, who will in turn produce some really important by-products as they make use of that fibre (short chain fatty acids) which are of huge benefit to our health. Interestingly, you often see gut issues and mental health issues occurring together in the same individuals.
Right, so we know that a healthier diet is strongly associated with better mental health, we know something about how nutrients exert their influence on our mental health. Where does the research go from here?
Well, I’m glad you asked…
In 2017, an intervention study was undertaken at the Food and Mood Centre in Australia. It was called the SMILES trial, which stands for “Supporting the Modification of lifestyle In Lowered Emotional States”. Fifty-six participants completed the trial, which consisted of two groups – one receiving social support and the other receiving dietary support to follow a modified Mediterranean diet. This involved eating a diet based on a certain number of serves per week of wholegrains, veg, fruit, legumes, low fat unflavoured dairy products, raw unsalted nuts, fish, lean meats, chicken, eggs and olive oil. The diet was designed to be easy to follow, tasty, sustainable and filling, and participants were told to eat with no calorie restrictions, as there was no weight loss focus to the study.
At the end of the 12-week trial, almost a third of the dietary intervention group were no longer considered clinically depressed (measured against the diagnostic criteria), compared to only 8% in the social support group. Pretty impressive results, and I’m hoping this might be repeated in a larger study.
There was some criticism of the recruitment process of the study, around creating an expectation amongst participants and potentially affecting the size of the outcome, but even taking this into consideration there are certainly no downsides to improving your diet, and it seems there is a very good chance of it having a positive impact on your mood.
Further to that research, in 2018 there was a review paper that analysed the results of 41 studies looking at various healthy eating patterns and the risk of depression. This review found benefits with all the diets studied, but it found the strongest benefit in following a Mediterranean-style dietary pattern, further supporting the metal health benefits of this way of eating.
That’s all great, but how do you apply it to your life?
Top 5 tips to support your mental health with food:
1. Eat more wholegrains: choose breads, cereals, wraps, rolls and crackers with at least 5 grams of fibre per 100 grams, and throw in some brown rice, quinoa, barley and bulgur wheat while you’re at it. Here's some great tips from the Heart Foundation on how to work more wholegrains into your day.
2. Eat more fruit and veg: smash that 5 plus a day by eating a piece of fruit with breakfast, or as a snack through the day, by adding more veg to your lunches and dinners. 5+ A Day have loads of awesome ways you can bump up your daily total in all your meals and snacks.
3. Eat more legumes: things like chickpeas, lentils, canned beans can be thrown into casseroles and other one-pot dishes to stretch the meat, or into salads to add fibre, vitamins, minerals and texture. The Dietitians Association of Australia list some great ways to use legumes in your meals.
4. Eat more healthy fats: fats found in oily fish, nuts and seeds are a feature of the Mediterranean diet. Find out all about choosing healthy fats on the Heart Foundation of Australia page.
5. Eat fewer processed foods: these foods certainly aren’t on any kind of “banned” list – there’s no such thing, and there’s room for all foods in a varied diet, just make sure they don’t displace the kind of foods your body needs to support good mental health.
While you're at it, head on over to the Mental Health Foundation's website to see what's on for Mental Health Awareness Week.
For all the nerds out there (hi!) that might want some further reading:
I found a great site while researching this blog, that I'm keen to explore further - Gut Microbiota for Health, and Professor Felice Jacka has written a book called Brain Changer (my copy just arrived in the post from Book Depository, so I've added it to the huge pile of books I intend to read...).
Take care :-)
References:
Bastiaanssen,T.F.S., Cowan, C.S.M., Claesson, M.J., Dinan, T.G., & Cryan, J.F. (2019). Making Sense of … the Microbiome in Psychiatry. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6313131/pdf/pyy067.pdf
Campbell, K. (2017). Breaking it down: Short-chain fatty acids and your health. Retrieved September 1, 2019, from the Gut Microbiota for Health website https://www.gutmicrobiotaforhealth.com/en/breaking-short-chain-fatty-acids-health/
Global Burden of Disease 2017 diet collaborators. (2017). Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. Retrieved from https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(19)30041-8.pdf
Jacka, F.N., et al. (2011). A Prospective Study of Diet Quality and Mental Health in Adolescents. Retrieved from https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0024805&type=printable
Jacka, F.N., et al. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). Retrieved from https://bmcmedicine.biomedcentral.com/track/pdf/10.1186/s12916-017-0791-y
Jacka, F.N., et al. (2010). Association of Western and Traditional Diets With Depression and Anxiety in Women. Retrieved from https://ajp.psychiatryonline.org/doi/full/10.1176/appi.ajp.2009.09060881?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed
Lassale, C., Batty, G.D., Baghdadli, A., Jacka, F., Sánchez-Villegas, A., Kivimäki, M., & Akbaraly, T. (2019). Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Retrieved from https://www.nature.com/articles/s41380-018-0237-8
Lozano, R., et al. (2012). Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Retrieved from http://dro.deakin.edu.au/eserv/DU:30050819/ortblad-globalandregional-2012.pdf
Molendijk, M.L., Fried, E.I., & Van der Does, W. (2018). The SMILES trial: do undisclosed recruitment practices explain the remarkably large effect? Retrieved from https://bmcmedicine.biomedcentral.com/track/pdf/10.1186/s12916-018-1221-5
Murray, C.J.L., Lopez, A.D., & Jamison, D.T. (1994). The global burden of disease in 1990: summary results, sensitivity analysis and future directions. Retrieved from https://pdfs.semanticscholar.org/2a29/edd9431b48857d9bb0f63d62d1936f0c512f.pdf Pasco, J.A., et al. (2010). Association of high-sensitivity C-reactive protein
with de novo major depression. Retrieved from https://pdfs.semanticscholar.org/64fb/a77b282f58134d22f6d21bb763a331701786.pdf?_ga=2.218507545.1688181233.1567308241-551446655.1567308241
Whiteford, H.A., Ferrari, A.J., Degenhardt, L., Feigin, V., & Vos, T. (2015). The Global Burden of Mental, Neurological and Substance Use Disorders: An Analysis from the Global Burden of Disease Study 2010. Retrieved from