Low mood is defined by the NHS as any of the following - sadness, anxiety, tiredness, struggling to sleep, anger and low self-esteem (1). When symptoms persist for more than two weeks this could indicate depression (1). In order to help us be more mentally resilient, it is important to factor in the role nutrition plays in our health and wellbeing.
The food we consume now and especially in the West, has shifted from pre-agricultural foods found in the wild to post-industrial semi- and ultra-processed foods. Our bodies are not able to keep up with this relatively rapid change and as a result, these altered foods have negatively impacted gut health (2). The human gut contains a variety of microbes, but imbalance caused by the Western-style diet is affecting of our gut microbiota and in turn, negatively impacting digestive function and our immune systems. When this happens, our brains develop an inflammatory response, which can result in depressive behaviour and even psychiatric disease (2). A recent study of data gathered from over 150,000 people found that inflammation was associated with low mood, inability to feel pleasure, fatigue, altered sleep and changes in appetite (3). However, other factors such as smoking and lifestyle (particularly stress) are also associated with inflammation and low mood (4).
Population-based studies have shown how stress can lead to emotional eating (usually reported more often by females) and negatively influences food choices – predominantly foods and drinks containing high amounts of sugar, refined carbohydrates (e.g. crisps, chips) and unhealthy fats (e.g. trans-fats, ultra-processed vegetable and seed oils) (5,6). In return, such foods impact mood but also promote a pro-inflammatory response in the body; and so develops a vicious cycle of stress, diet and inflammation (6).
Kiecolt-Glaser, 2010
Serotonin, often known as the happy hormone, plays an important role in the communication between the gut and the brain. In fact, 95% of serotonin is actually produced in the gut (7). When people are stressed, this impacts serotonin levels and in turn, leads to constipation or diarrhoea in addition to other symptoms such as bloating or pain – this is due to the gut-brain axis, which refers to the physical and chemical connections that link these two organs (6). Studies have suggested that probiotics (beneficial live bacteria and yeasts) improve cognitive impairment such as difficulties in concentration, as well as depressive disorders (8). A study on older adults found probiotics to have alleviated stress and caused changes in the gut microbiota (8).
In order to overcome the negative roundabout of stress, diet and inflammation, throw away sugary cereals, sweets, biscuits, pastries, crisps, chips and ready-made meals and avoid/minimise the number of times you eat takeaways/fast food. Instead, eat more foods that contain antioxidants - molecules that fight excess free radicals in the body that can lead to oxidative stress and eventually chronic inflammation. A great example of a diet high in antioxidants, as well as being minimally processed is the Mediterranean-style diet which consists of fibre-rich vegetables, fruits, nuts and seeds, healthy fats and protein sources. In addition, you can give your gut health a leg-up by eating fermented drinks or foods such as kefir or kimchi and/or a multi-strain probiotic as well as boost your serotonin levels with exercise and exposure to natural light.
NHS. UK (2019) Low mood, sadness and depression
2. Olmo et al. (2021) Evolution of the Human Diet and Its Impact on Gut Microbiota, Immune Responses, and Brain Health. Nutrients, 13(1), 196.
Milaneschi et al. (2021) Association of Inflammation with Depression and Anxiety: Evidence for Symptom-Specificity and Potential Causality from UK Biobank and NESDA Cohorts. MedRxiv
Chimenti et al. (2021) The burden of depressive disorders in musculoskeletal diseases: is there an association between mood and inflammation? Ann Gen Psychiatry 20, 1.
Bemanian et al. (2020) Emotional Eating in Relation to Worries and Psychological Distress Amid the COVID-19 Pandemic: A Population-Based Survey on Adults in Norway. Int J Environ Res Public Health, 18(1), 130.
Kiecolt-Glaser (2010) Stress, Food, and Inflammation: Psychoneuroimmunology and Nutrition at the Cutting Edge. Psychosom Med, 72(4), 365-369.
Carpenter (2012) That gut feeling. American Psychological Association, 4398), 50.
Chong-Su Kim et al. (2021) Probiotic Supplementation Improves Cognitive Function and Mood with Changes in Gut Microbiota in Community-Dwelling Older Adults: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial. The Journals of Gerontology: Series A, 76(1), 32–40.