How Your Diet Affects Your Mental State

How Your Diet Affects Your Mental State?

During the COVID-19 pandemic, an alarming 65.6% of Hong Kong residents who participated in a case study have reported clinical levels of depression, anxiety, and/or stress. (1) Prevalence of depression was also highest in university students in our city (41%) compared to students in China and Macau. Can the food we eat play a role in improving our mood and wellbeing? 

Food is not only necessary as a metabolic fuel for the body- current evidence suggests that there is a link between diet and mental health. Let’s look at specific nutrients and dietary patterns that play a role in regulating our mood and cognition.

1. Carbohydrates Are The Fuel For Our Brain

Glucose is essentially the sole fuel for our brain, except during prolonged starvation, allowing us to be able to concentrate and focus. The brain consumes about 120 grams of glucose daily (4). We can obtain glucose from different food sources including grains, fruits, sugars and lactose in milk. Healthy carbohydrate-rich options such as wholegrains, vegetables, fruits, legumes and low-fat dairy foods. These are also important sources of other nutrients, such as calcium and B vitamins. When we don’t eat enough carbohydrates, our blood glucose can be low (hypoglycemia), which may lead to feelings of dizziness, fatigue and inability to concentrate.

2. Take A Load Off: Lower Glycemic Load For Better Mood

The Glycemic Index (GI) is a value given to carbohydrate-rich foods which reflects how they affect your blood glucose levels. The Glycemic Load (GL) is a measure of both the quality (the GI value) and quantity (grams per serve) of carbohydrates in a meal. It is a more complete and useful picture of how a particular food, in a specific quantity, will affect our blood sugar level. Choosing low GI carbohydrates at each meal may help to keep hunger at bay for longer after eating and provide a gradual, continuous supply of energy from one meal to the next.  A high-glycemic load diet was associated with higher depression symptoms, total mood disturbance, and fatigue compared to a low-glycemic load diet in overweight/obese, but otherwise healthy adults (5). Swap white rice, bread and noodles to lower GI options such as brown rice, whole grain bread, wholewheat pasta, oats, dried beans and lentils.

3. Boost Serotonin With Tryptophan-rich Foods

Tryptophan is an essential amino acid and is the precursor for the production of neurotransmitter serotonin, which plays a role in regulating our sleep, appetite, and impulse control. Excellent sources of tryptophan include turkey, chicken, eggs, cheese, pumpkin seeds and soy-based products. In addition, having carbohydrates with these foods help more tryptophan across the blood-brain-barrier, producing more serotonin in the brain.

4. Stabilise Your Mood By Consuming Omega-3 Fatty Acids 

Studies have shown that individuals diagnosed with depression had lower blood levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (6). Supplementation of these omega-3 fatty acids have shown beneficial effects on depressive symptoms (7). We should have oily fish at least twice a week as they have the highest levels of EPA and DHA. Mark your calendars and incorporate these oily fish into your diet: salmon, trout, mackerel, sardines and swordfish.

5. Folate Is Crucial For Serotonin And Dopamine Production

Folate deficiency can contribute to a depressed mood. Folate is responsible for the synthesis of s-adenosylmethionine (SAM), which is the major methyl group donor for methylation reactions. In the brain, these reactions are crucial for the synthesis of neurotransmitters such as serotonin and dopamine. Good sources of folate include dark green leafy vegetables, broccoli, chickpeas, kidney beans and fortified breakfast cereals. 

6. Probiotics May Help Improve Depression Severity

Gut probiotics play a major role in bidirectional communication between the gut and the brain. A systematic review suggested the role of probiotics in reducing depression risk in non-depressed individuals (8). Moreover, altering the gut-brain axis with probiotics may be an approach to improve depression severity (9). The majority of fermented foods providing probiotics are high in salt due its role in the fermentation process. Lower sodium sources of probiotics can be found naturally in low-fat yoghurt, kefir, tempeh.

Diet patterns

In general, a ‘western’ dietary pattern, characterised by a high consumption of sweetened beverages, refined food, fried food, processed meat, refined grain, and high fat intake, biscuit snacking and pastries, has been associated with an increased prevalence of depression. On the other hand, a diet high in olive oil, fish, fruits, vegetables, nuts, legumes, poultry, dairy, unprocessed meat, for example the Mediterranean diet, have been inversely associated with depression risk (2). Such a diet was also shown to reduce depressive symptoms in adults with depression (3). 

In conclusion,
a diet containing wholegrains, oily fish, lots of fruit and vegetables is associated with better mood outcomes. We hope you will make the necessary alterations in your diet to have good physical and mental health. Besides, consider balancing physical activities and food intake to beat the pandemic blues.

1) Tso & Park (2020) Alarming levels of psychiatric symptoms and the role of loneliness during the COVID-19 epidemic: A case study of Hong Kong. Psychiatry Research 293:113423. 

2) Lang et al. (2015) Nutritional Aspects of Depression. Cellular Physiology and Biochemistry 37:1029-1043 

3) Jacka et al (2017) A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Medicine 15, 23 

4) Berg et al (2002)  Biochemistry. 5th edition. New York: W H Freeman; Section 30.2, Each Organ Has a Unique Metabolic Profile. Available from: 

5) Breymeyer et al (2016) Subjective mood and energy levels of healthy weight and overweight/obese healthy adults on high-and low-glycemic load experimental diets. Appetite 107:253-259 

6) Larrieu & Layé (2018). Food for Mood: Relevance of Nutritional Omega-3 Fatty Acids for Depression and Anxiety. Frontiers in Physiology, 9, 1047. 

7) Liao et al (2019) Efficacy of omega-3 PUFAs in depression: A meta-analysis. Translational Psychiatry 9, 190. 

8) Huang et al (2016) Effect of Probiotics on Depression: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients 8, 483. 

9) Goh et al. (2010) Effect of probiotics on depressive symptoms: A meta-     analysis of human studies. Psychiatry Research 282, 112568.

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