The link between the food we eat and our mental health.
The situation
Mental health conditions are on the rise and the amount of antidepressants being prescribed are at an all-time high 1.
According to the Global Burden of Disease Study diet is thought to be the leading cause of early death in men and the second largest in women whilst mental health disorders are the leading cause of disability 2. There is a clear link between the worsening of our diets and the rise in mental health and we are yet to realise the enormity of the problem. There is no economy in the world that can render the costs of an unhealthy diet if the trajectory continues in this fashion.
The food industry is largely to blame 3,4. Large public sector companies are continuing to make profits for mass producing foods that are high in refined sugars, highly processed and full of additives. These foods are cleverly designed by scientists to stimulate the reward centre of our brain; reinforcing the eating behaviour and triggering us to continue to eat these types of food. This is fuelling obesity and associated chronic health conditions 3.
Whilst the food industry is a problem, another problem is our approach to medicine. Historically, doctors were taught to treat or suppress the symptom in order to cure the illness 5. This type of approach cannot be used for treating chronic inflammatory conditions, whereby most risk factors are subject to our diet and lifestyle. You can prescribe an anti-depressant to lift your mood or you can give a statin to reduce your cholesterol but if you don’t treat the root cause of the problem symptoms may manifest elsewhere. As more evidence is highlighting the role of diet in our mental health, it is time we take a more rounded approach towards medicine, starting with addressing our lifestyles.
Could changing my diet help my mental health condition?
Many mental health conditions are related to childhood trauma, family complications, bereavement – things to which you often cannot change. However, the dramatic increases in mental health conditions we are now seeing, which is different to previous decades, are being put down to the changes in our lifestyles, i.e: more sedentary, worse diets, less social connections. Our lifestyle and diet are modifiable risk factors for depression and anxiety. which we do have the power to change.
Many studies have observed the link between nutrition and mental health related conditions however the SMILES Trial, conducted by Jacka et al., 2017, was the first controlled research study to investigate the effect of nutrition on clinically diagnosed depression 6. In this trial participants were assigned to one of two groups: a counselling or dietary support. Those in the dietary support group were instructed to follow a version of the Mediterranean diet; focusing on increasing vegetables, fruit, wholegrain, legumes, oily fish and good fats whilst reducing refined sugar intake. The results were staggering. Within 12 weeks, 32% of individuals in the dietary intervention group achieved remission from clinically diagnosed depression compared to 8% in those who received counselling. The extent of dietary changes also correlated with extent of improvement.
This should not devalue counselling as a treatment, as some individuals still achieved remission this way. But it should demonstrate the power of dietary intervention and highlight the importance to consider this as a tool for prevention and rehabilitation.
More and more studies are beginning to demonstrate the links between our food and our mood, and the positive impact that dietary changes can have in treatment of anxiety and depression 7,8.
What is the link between mood and food?
The Gut microbiome
The gut microbiome is made up of trillions of microorganisms such as bacteria, viruses and yeast. Many of these microorganisms perform essential functions within the body; protect us against pathogens, produce vitamins and hormones, modulate our immune response, digest nutrients, eliminate toxins and even has key roles in our brain health. This is due to the gut brain axis, the term used to describe the communication between the gut and the brain.
The bacteria in the gut break down fibrous foods; vegetables, fruits, wholegrains, legumes via the process fermentation. During the fermentation process different metabolite are produced. It is these metabolites that interact with each cell in our body and is the reason why the health of the microbiome and our bacteria have such systemic effects.
We know from research that the health of the microbiota is determined by the diversity of our diet. A diet high in diversity = microbiome high in diversity = better health outcomes. Work has shown that people with depression have a significantly less diverse microbiota. A westernised diet, high in processed foods and refined sugars can reduce the diversity of the microbiota. Microbes in the gut are responsible for producing neurotransmitters, such as serotonin and dopamine – our happy hormones – therefore disruption to the microbiome can reduce the production of these hormones and subsequently impact our mood. Such disruption can also reduce our ability to fight infect and increase inflammation; both further factors that are implicated in depression and anxiety 9,10.
Inflammation
Inflammation has been recognised as a key driver for mental and chronic health conditions 8,11. One of the main drivers of inflammation is diet. A nutrient poor diet and one high in refined sugars, typical of a western diet, is known to increase inflammation. Inflammation can cause damage all over the body from thickening of arteries; a risk for cardiovascular disease to over activating the immune system. But it can also have direct effects on our brain:
- Increase the level of inflammatory markers which can affect the release of serotonin and dopamine, our feel good hormones and dyresgulate our stress response
- Disrupt the microbiome, contributing to the above effects
- Decrease hippocampal volume, the area involved in processing of emotional responses
- Damage neurons within the brain; increasing vulnerability to depression
Brain plasticity
Dietary interventions are thought to be effective inducers of brain plasticity 12. Plasticity refers to the brains ability to change and adapt in response to certain stimuli by reorganising structure and connections. Whilst brain plasticity is key for learning and memory it is also important for mental health. Plasticity helps us to make healthy behaviours and experience positive emotions. In mental illness, it is thought that maladaptive plasticity occurs.
What you eat can either positively or negatively impact plasticity with a brain healthy diet; rich in polyphenols and omega 3 fatty acids, improving brain plasticity and thus, mental health conditions. However, a poor diet, high in refined sugars, inhibits plasticity adding stress to the brain, inadvertently contributing to mental health related conditions.
So, what can we do to support our brain health?
Increase variety. This is one of the most beneficial things you can do to improve the health of your microbiome and therefore, your brain.
- Constantly switch the varieties of fruits, vegetables, wholegrains, beans, seeds, nuts and legumes you are eating
- Challenge yourself to 30 different vegetable and fruit varieties per week
Reduce the amount of refined sugars and carbohydrates. These food groups: trigger brain inflammation, disrupt the microbiome and impact brain plasticity
- Try and look for whole foods, such as grains: quinoa, wholegrain rice, bulgur wheat, chickpeas
- Recognise all the ingredients on the back of packet
- Make sure there are less than 5 ingredients within a product
Increase the amount of polyphenols: these are the compounds contained in plant-based foods.
- Fruits such as dark berries
- Vegetables such as spinach, kale, swiss chard, broccoli, onion, artichokes
- Dark chocolate (>80% cocoa)
- Nuts
Increase omega-3 fatty acids: not only are they a potent anti-inflammatory, they also help in the formation of new neurons
- Mackerel, sardines, salmon, herring
- Flaxseeds and hempseeds
- Algae and seaweed
Increase fibre: this is the quickest and best way to influence the composition of your microbiome
- Vegetables – virtually any!
- Wholegrains – oatmeal, bulgur, barley, brown rice
- Legumes – chickpeas, beans, lentils, peas
- Fruits – berries, apples, bananas, oranges
If there was one ‘diet’ to adopt for better brain health it would be the Mediterranean:
- Wide variety of fruit and vegetables
- Complex carbohydrates/ grains
- Regular oily fish consumption, e.g. salmon, mackerel, sardines, anchovies
- Extra virgin olive oil
- Nuts and seeds
- Moderate alcohol, dark red wine being preferential
- Take time to relax and enjoy food
Consider fasting principles. Whether this be following a 12/14 hour overnight fast or trying to go 5 hours in between meals. We are not evolved to continuously graze and this can drive inflammation, reduce brain plasticity and cause considerable alterations to microbiome. Fasting gives opportunity for our cells and microbiota to rest and recover, reducing inflammation and repairing. Note: before adopting any fasting principles please speak to relevant healthcare professional as some populations should not be engaging with fasting.
Historically, research has focused on how the foods we eat affect our physical health. We are only just beginning to learn about how food is influencing our mental health. My clinic focuses on using nutrition and lifestyle interventions for mental health and chronic health conditions. If you would like to hear more, please get in touch: info@melaniewilkinsonnutrition.com
References:
1. Depression. (2021). Retrieved 29 November 2021, from https://www.who.int/news-room/fact-sheets/detail/depression
2. Ouyang, G., Pan, G., Liu, Q., Wu, Y., Liu, Z., & Lu, W. et al. (2020). The global, regional, and national burden of pancreatitis in 195 countries and territories, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. BMC Medicine, 18(1). doi: 10.1186/s12916-020-01859-5
3. White, M., Aguirre, E., Finegood, D., Holmes, C., Sacks, G., & Smith, R. (2020). What role should the commercial food system play in promoting health through better diet?. BMJ, m545. doi: 10.1136/bmj.m545
4. Monteiro, C., Moubarac, J., Cannon, G., Ng, S., & Popkin, B. (2013). Ultra-processed products are becoming dominant in the global food system. Obesity Reviews, 14, 21-28. doi: 10.1111/obr.12107
5. Is it possible to make diseases disappear? – Dr Rangan Chatterjee. (2016). Retrieved 29 November 2021, from https://drchatterjee.com/video-is-it-possible-to-make-diseases-disappear/
6. Jacka, F., O’Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., & Mohebbi, M. et al. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Medicine, 15(1). doi: 10.1186/s12916-017-0791-y
7. The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials: Erratum. (2020). Psychosomatic Medicine, 82(5), 536-536. doi: 10.1097/psy.0000000000000807
8. Lassale, C., Batty, G., Baghdadli, A., Jacka, F., Sánchez-Villegas, A., Kivimäki, M., & Akbaraly, T. (2018).Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Molecular Psychiatry, 24(7), 1094-1094. doi: 10.1038/s41380-018-0299-7
9. Dinan, T., & Cryan, J. (2017). Brain–gut–microbiota axis — mood, metabolism and behaviour. Nature Reviews Gastroenterology & Hepatology, 14(2), 69-70. doi: 10.1038/nrgastro.2016.200
10. Kronsten, V., Tranah, T., Pariante, C., & Shawcross, D. (2021). Gut-derived systemic inflammation as a driver of depression in chronic liver disease. Journal Of Hepatology. doi: 10.1016/j.jhep.2021.11.008
11. Kim, J., Kim, H., & Song, S. (2018). Associations among inflammation, mental health, and quality of life in adults with metabolic syndrome. Diabetology & Metabolic Syndrome, 10(1). doi: 10.1186/s13098-018-0367-9
12. Murphy, T., Dias, G., & Thuret, S. (2014). Effects of Diet on Brain Plasticity in Animal and Human Studies: Mind the Gap. Neural Plasticity, 2014, 1-32. doi: 10.1155/2014/563160