You’ve probably heard of the saying “good food, good mood”, but what does this mean? Is there any science to back up this common saying or is it just that, a saying? There are many ways in which a healthy diet can affect our mental health. One such mechanism that can help improve our mental wellbeing through food is known as the gut-brain axis (Oriach et al., 2016).
The gut-brain axis is bidirectional, meaning the brain can play a role in intestinal activities and our gut microbiome can influence our mood, our cognition, and our mental health (Appleton 2018). Anxiety and mood disorders linked to gastrointestinal (GI) disruptions is one example of this communication system at work, while GI disorders like irritable bowel syndrome (IBS) that can often be linked to physiological stresses that influence the gut microbiota is a second example.
So how can we support our gut microbiome and our mental health?
The Mediterranean Diet
Studies have shown that there may be a link between following a Mediterranean diet and improved mental health and wellbeing (Skarupski et al., 2013, Moreno-Agostino 2018). This diet involves consuming fresh fruit and vegetables, nuts, legumes, wholegrains, oils, and fish while eating little processed foods and red meat. The nutrients believed to have a connection with mental health are Omega 3 and 6, and fibre.
Omega-3 and omega-6 are essential fatty acids found in oily fish that are known for playing a role in physical health but are also essential for brain function. Recently studies have linked low levels of these important nutrients to anxiety and depression (Parletta et al., 2019, Lesperance et al., 2010). It is currently recommended to eat one to two portions of oily fish a week. For those following a plant-based diet, or if you simply do not like fish there are still foods you can consume to meet weekly recommendations. Examples are chia seeds, walnuts, and flaxseed.
Dietary fibre is a key component of the Mediterranean diet and is a nutrient that is under consumed within the UK. Dietary fibre is known to feed our gut and it is therefore necessary for our gut microbiome to have optimal function. When inadequate levels of fibre are consumed, it can lead to an imbalanced gut and a reduced diversity of the microbiota (Koc et al., 2020). Studies have confirmed the significant role dietary fibre plays in regulating the gut and while there is no direct link between dietary fibre and mental health, if we don’t feed our gut microbiome the correct nutrients this can have a negative effect on our mental health (Sun et al., 2020, Du Toit 2019).
Probiotics
In 2002 an expert panel defined probiotics as live microorganisms that when consumed in adequate amounts can improve the health of the person consuming them (Reid et al. 2019). This definition has not changed since then. Fermented foods are the main source of probiotics in the human diet. Probiotics and the connection with mental health is a very new area of research but preliminary studies have found that probiotics have a beneficial effect on mental health (Mohammadi et al., 2015). Studies have found that the consumption of these ‘healthy bacteria’ can have a similar effect as antidepressants on our brain (Tillisch et al., 2013). One key area of probiotics research is on major depressive disorder. Studies have shown that the use of probiotics whether as a standalone or alongside antidepressants has a positive effect on mental health (Johnson et al., 2021).
Hydration
Studies looking into hydration and mood are new, but some suggest that dehydration is linked to a reduction in cognitive performance and mood (Masento et al., 2014). Water is the most important fluid for hydration but tea, coffee, sugar free drinks and low-fat milk can improve our hydration status. While coffee is considered a part of our fluid intake it is important to note coffee can influence our mood in different ways. Person dependent, coffee can increase alertness and can improve mood but, in some cases, coffee can also increase anxiety (Nehlig 2016).
Dietary Advice
Studies have shown a connection between diet and mental health. So, what amounts of these nutrients should we be consuming?
- It is currently recommended to eat one to two portions of oily fish a week.
- Some examples of oily fish are mackerel, tuna, sardines, and salmon.
- You may need to consider a supplement if you are not getting enough omega-3 or 6 from your diet.
- As part of a healthy diet 30mg of dietary fibre should be consumed daily.
- Examples of foods high in fibre are fruit and vegetables, potato skins and wholegrain foods like brown pasta and brown rice.
- Using the phrase ‘high in fibre’ is unregulated in the UK meaning many products are falsely claiming this. Check the nutritional labels to ensure foods are high in fibre.
- If increasing the amount of fibre consumed, it should be done gradually to avoid certain gut issues like bloating and gas.
- Fermented foods should be included in the diet to increase good bacteria and to help improve gut health.
- Examples of foods containing these good bacteria are yoghurts, kefir, kombucha, tempeh and pickles.
- Look for foods labelled as having ‘live cultures’ or ‘active cultures’ to ensure they are probiotic.
- It is recommended to drink 6-8 glasses of water a day. In hot weather or when physical activity is taking place this should be increased by 2 glasses.
- Up to 300mg of caffein a day is considered safe, while pregnant this is reduced to 200mg a day.
- Speak to a qualified nutritionist or dietician if you are thinking about taking a supplement.
The relationship between food and mood is complex with more research needed to gain a greater understanding of the underlying mechanisms. Consuming a diet rich in a variety of nutrients, that satisfy our own personal food preferences, will likely help improve our mood. You can find a list of registered dieticians and nutritionists online via The British Dietetics Association and The Association for Nutrition if you require nutritional support.
While nutrition and diet have been proven to have a connection to our mood, we cannot completely rule out modern medicine. Speak to a GP if you think you are suffering from anxiety or depression.
References:
Appleton J. (2018). The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. Integrative medicine (Encinitas, Calif.), 17(4), 28–32.
Du Toit, A., 2019. The gut microbiome and mental health. Nature Reviews Microbiology, 17(4), pp.196-196.
Johnson, D., Thurairajasingam, S., Letchumanan, V., Chan, K. and Lee, L., 2021. Exploring the Role and Potential of Probiotics in the Field of Mental Health: Major Depressive Disorder. Nutrients, 13(5), p.1728.
Koc, F., Mills, S., Strain, C., Ross, R. and Stanton, C., 2020. The public health rationale for increasing dietary fibre: Health benefits with a focus on gut microbiota. Nutrition Bulletin, 45(3), pp.294-308.
Lespérance, F., Frasure-Smith, N., St-André, E., Turecki, G., Lespérance, P. and Wisniewski, S., 2010. The Efficacy of Omega-3 Supplementation for Major Depression. The Journal of Clinical Psychiatry, 72(08), pp.1054-1062.
Masento, N., Golightly, M., Field, D., Butler, L. and van Reekum, C., 2014. Effects of hydration status on cognitive performance and mood. British Journal of Nutrition, 111(10), pp.1841-1852.
Mohammadi, A., Jazayeri, S., Khosravi-Darani, K., Solati, Z., Mohammadpour, N., Asemi, Z., Adab, Z., Djalali, M., Tehrani-Doost, M., Hosseini, M. and Eghtesadi, S., 2015. The effects of probiotics on mental health and hypothalamic–pituitary–adrenal axis: A randomized, double-blind, placebo-controlled trial in petrochemical workers. Nutritional Neuroscience, 19(9), pp.387-395.
Moreno-Agostino, D., Caballero, F., Martín-María, N., Tyrovolas, S., López-García, P., Rodríguez-Artalejo, F., Haro, J., Ayuso-Mateos, J. and Miret, M., 2018. Mediterranean diet and wellbeing: evidence from a nationwide survey. Psychology & Health, 34(3), pp.321-335.
Nehlig, A., 2015. Effects of coffee/caffeine on brain health and disease: What should I tell my patients?. Practical Neurology, 16(2), pp.89-95.
Oriach, C., Robertson, R., Stanton, C., Cryan, J. and Dinan, T., 2016. Food for thought: The role of nutrition in the microbiota-gut–brain axis. Clinical Nutrition Experimental, 6, pp.25-38.
Parletta, N., Zarnowiecki, D., Cho, J., Wilson, A., Bogomolova, S., Villani, A., Itsiopoulos, C., Niyonsenga, T., Blunden, S., Meyer, B., Segal, L., Baune, B. and O’Dea, K., 2017. A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional Neuroscience, 22(7), pp.474-487.
Reid, G., Gadir, A. and Dhir, R., 2019. Probiotics: Reiterating What They Are and What They Are Not. Frontiers in Microbiology.
Skarupski, K., Tangney, C., Li, H., Evans, D. and Morris, M., 2013. Mediterranean diet and depressive symptoms among older adults over time. The journal of nutrition, health & aging, 17(5), pp.441-445.
Sun, Y., Cheng, L., Zeng, X., Zhang, X., Liu, Y., Wu, Z. and Weng, P., 2021. The intervention of unique plant polysaccharides – Dietary fiber on depression from the gut-brain axis. International Journal of Biological Macromolecules, 170, pp.336-342.
Tillisch, K., Labus, J., Kilpatrick, L., Jiang, Z., Stains, J., Ebrat, B., Guyonnet, D., Legrain–Raspaud, S., Trotin, B., Naliboff, B. and Mayer, E., 2013. Consumption of Fermented Milk Product With Probiotic Modulates Brain Activity. Gastroenterology, 144(7), pp.1394-1401.e4.