A susceptibility to depression is driven by various factors: genetic, hormonal, immunological, biochemical and neurodegenerative. The food we eat on a daily basis – a diet – modulates each of these factors and subsequently the research 1;  Jacka, F. N., Pasco, J. A., Mykletun, A., Williams, L. J., Hodge, A. M., O’Reilly, S. L., … Berk, M. (2010). Association of Western and Traditional Diets With Depression and Anxiety in Women. American Journal of Psychiatry, 167(3), 305–311. doi:10.1176/appi.ajp.2009.0906088 2 Tina Ljungberg, Emma Bondza and Connie Lethin; Evidence of the Importance of Dietary Habits Regarding Depressive Symptoms and Depression; Int J Environ Res Public Health. 2020 Mar; 17(5): 1616.; Published online 2020 Mar 2. doi: 10.3390/ijerph17051616 has shown that dietary interventions can essentially contribute to depression prevention and treatment because food products have a credible impact on development and course of depression.

If we can mitigate or prevent the symptoms of depression through our daily habits, including changes in diet, there is a higher likelihood that we will be more motivated to build healthy lifestyle habits.

What are the grounds for such statement? Even though intestinal bacteria are not an individual organ, they are certainly a key “player” in our body. It is assumed that they amount to 50 trillion or approximately 1.3 times more than all somatic cells in total. It means 360 genes of microorganisms against each of ours. Their weight can sum up to as much as three kilograms, and there are roughly 500 species which are connected in a complex ecosystem – microbiome. Just like in any natural environment – as soon as the balance is lost, it affects the condition of other related systems. What is related with intestines?

Around 100 million of intestinal neurons are directly connected to the brain through gut-brain axis. We know that gut bacteria regulate immunity and metabolism, and it is involved in synthesis of vitamins, hormones and neurotransmitters. No doubt, it all has a bearing on the brain 3 The Grain Brain Whole Life Plan: Boost Brain Performance, Lose Weight, and Achieve Optimal Health Preloaded; by M.D. Perlmutter, David (Author), Kristin Loberg; 2015 .No matter how interesting, it is a different topic. Even though we can discern three factors vital for mental health nutrition:

1. Intestinal microbiome consists of several large groups of bacteria. Each of these groups has their functions and they are responsible for producing special enzymes.
2. Food we eat nourishes not only us but also our intestinal bacteria. Each group of bacteria “prefers” certain foods. Nutrition disbalance changes ratio of bacteria, because some of them are left without food, and some on the other hand are overfed leading to rapid expansion.
3. People suffering from depression have been found to present serious alterations in intestinal microbiome: they have microbiome which aggravates “inflammatory processes" and reduces colony of bacteria responsible for synthesising serotonin, the “happy hormone”.

What are the conclusions? Firstly, we must cut down the products that feed the opportunistic bacteria and provide food for the beneficial ones with potentially healthy products they have chosen over the course of evolution.

So, we have arrived at foods which are recommended to prevent depression symptoms. There was an interesting study 4 Laura R LaChance and Drew Ramsey; Antidepressant foods: An evidence-based nutrient profiling system for depression; World J Psychiatry. 2018 Sep 20; 8(3): 97–104.; Published online 2018 Sep 20.; doi:10.5498/wjp.v8.i3.97 which looked at food categories and level of antidepressant properties they possess, and it was found out that vegetables are a group of products with the highest score (48%).

However, it was also concluded that results cannot be achieved quickly. A study 5 Felice N. Jacka, Adrienne O’Neil, Rachelle Opie, Catherine Itsiopoulos, Sue Cotton, Mohammedreza Mohebbi, David Castle, Sarah Dash, Cathrine Mihalopoulos, Mary Lou Chatterton, Laima Brazionis, Olivia M. Dean, Allison M. Hodge & Michael Berk; A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial); BMC Medicine volume 15, Article number: 23 (2017); Open Access; Published: 30 January 2017 revealed that medium or severe depression patients should eat more healthy foods at least for 12 weeks to see symptoms improve and the menu should include more raw and wholegrain foods, which contain a lot of nutrients. One must certainly restrict processed and refined foods, sweets, fried foods, incl. fast food. This study proved that one can reduce depression symptoms in more than 32% of cases by just changing the dietary habits.

Products to be avoided as much as possible:

Alcohol

There is a direct link between alcohol and mental health disorders. Some people drink alcohol to manage depression, nevertheless it can only exacerbate or trigger new and repeated episodes of depression and anxiety. Regular alcohol abuse in large quantities may cause additional complications, such as accidents, family problems, loss of work and poor health. It creates a vicious circle because the new problems eventually lead back to depression.

Refined products

This category includes fast food and unhealthy products (sugar and all industrial sweets, products from refined flour, ready-to-eat products: dumplings, chips, crackers, fish and meat imitation (especially crab sticks), margarine, soups, noodles and potato mash) because they have high-calories to low-nutrition-value ratio. The research reveals that people who predominantly eat fast food are more susceptible to depression than those who mainly eat freshly prepared meals.

Processed foods, especially ones containing plenty of sugar and refined carbohydrates may pose a higher risk of depression. When a person eats refined carbohydrates, body's energy levels spike and drop quickly; therefore, a chocolate bar may give an instant impetus, but it will be followed by a rapid decline.

Processed oils

The refined and saturated fats may deteriorate brain activity and aggravate depression symptoms. Fats to be definitely avoided include:

• transfats which are found in many food products;
• fats from red and processed meats;
• oils rich in omega-6 fatty acids (for example corn oil).

Caffeine

Caffeine is a product of heated debate. Different literature sources show opposite statements. It is believed that depressed people may start to feel favourable changes in their condition if they abstain from caffeinated drinks after lunch. Some research has revealed that depression patients may benefit from moderate caffeine intake. Benefits of caffeine could be found in its stimulating impact and antioxidant properties.

Caffeine is found in coffee, tea, chocolate, carbonated drinks, energy drinks.

Some proof exists confirming that small amounts of caffeine may reduce anxiety and improve mood. Meanwhile other research has shown that in secondary school pupils it may cause feelings of anxiety, stress and depression. Besides caffeine impacts a person's ability to fall asleep.

Given these controversial data, we would suggest to better:

• consume caffeine moderately;
• avoid high caffeine content products, such as energy drinks;
• avoid caffeine consumption after midday

Finally, we would like to suggest some things that would help in your struggle with depression:

1. find 150 minutes for physical activity every week;
2. go outside every day (even for short periods);
3. abstain from alcohol and other intoxicating substances;
4. devote 7-8 hours for sleep every night.

If these recommendations do not help to make you feel considerably better, perhaps you could benefit from food supplements, which contain plants and minerals  with antidepressant properties.

In any case, if you feel difficult to manage your depression, contact your physician as they will recommend suitable treatment to help you managing depression symptoms.