This article was written by one of The Food Medic team; registered dietitian – Maeve Hanan.
More interest is emerging about whether how we eat can impact our mood, or even help with the treatment of mood disorders like depression. Read on to learn more about this fascinating and important topic.
Nutrients For brain health
Nutrition plays an important role in the health of every organ in our body, including our brain. Nutrients both contribute to the structure and function of the brain in a number of ways.
Important nutrients for brain health include:
- Carbohydrates: These provide the best source of fuel for the brain and are needed for normal brain functioning such as memory, attention, alertness, mental and cognitive performance (1).
- Omega-3: This essential fatty acid plays an important role in brain development, the structure of brain cell membranes and has an antiinflammatory effect (2). This has been found to support brain functioning including cognition and mental state (3). See here for more information about omega-3.
- Protein: This nutrient is needed to create chemical messengers in the brain called neurotransmitters (4). For example, the amino acid tryptophan is needed for the production of serotonin (A.K.A. ‘the happy hormone’). But there’s no convincing evidence that consuming a high-tryptophan diet, beyond what a balanced diet provides, boosts brain function or mood.
- Minerals such as selenium, zinc, iron, magnesium are important for the brain, and low levels of zinc and iron in particular have been linked with depression (5, 6).
- B-vitamins are involved in nerve function, neurotransmitter creation, and vitamin B12 and folate deficiency in particular have been linked with worsened brain function and depression (7, 8, 9).
- Other vitamins also plan important roles. There is a possible link between vitamin D deficiency and cognitive issues and depression, but ongoing research is needed (10). Vitamin K is associated with improvements in cognition (11). Vitamin C and E are antioxidants that may be protective for the brain.
- Choline is found in a number of animal-based foods as well as soya beans, quinoa and shiitake mushrooms. This is important for creating a neurotransmitter called acetylcholine that is important for memory and other brain functions (12).
- Polyphenols are natural compounds found in a variety of colourful, mainly plant-based foods like berries, green leafy vegetables, as well as tea, coffee and dark chocolate. These are thought to be beneficial for the brain due to their antioxidant effect.
There is some evidence that taking some of these nutrients in supplement form may be beneficial as part of the treatment of depression, but never as the only treatment for depression, with the strongest current evidence linked to omega-3 supplements (13). Ongoing research is needed and the most important thing is avoiding deficiencies of these nutrients by consuming a balanced diet. However, in the UK and Ireland vitamin D supplements are often needed, especially during the winter.
But as we eat foods not individual nutrients, it’s always important to bring this back to actual food and dietary patterns. The Mediterranean diet is a great example of a way of eating that contains these brain-healthy nutrients, as well as other brain-healthy practices such as socialising, being activating and relaxing.
Foods that are typical of a traditional Mediterranean diet include:
- Fruit and vegetables – provides vitamins, minerals, fibre and antioxidants
- Wholegrains – contain carbohydrates, B-vitamins, minerals and fibre
- Legumes – provides protein and fibre
- Oily fish – great source of omega-3 and protein
- Nuts and seeds – contain protein, fibre and vitamin E
- Olive oil – provides unsaturated fats and antioxidants
- Herbs and spices – provides small amounts of antioxidants
Malnutrition & the brain
As nutrients play such an important role in brain function and structure, it’s unsurprising that being malnourished can lead to significant issues with brain health. In fact, the brain has been seen to shrink in size in response to malnutrition (14).
Studies related to eating disorders shed a lot of light on this area. For example, a study from 2012 of adolescents with anorexia nervosa found reductions in grey matter that improved in line with weight restoration (15).
Other studies of those with anorexia have also found changes in areas of the brain related to memory and emotional processing, decision-making and learning (16).
The SMILES trial
The SMILES Trail was a ground-breaking study from 2017 that found a link between dietary intake and improved mental health (17).
The involved 56 participants with moderate to severe depression who were divided into one of two study groups:
- Diet support group – ModiMed diet* with Dietetic support
- Social support group – befriending meet-ups
*The ModiMed diet is a combination of the Greek and Australian dietary guidelines with a traditional Mediterranean diet.
After 12 weeks, depression was measured using the Montgomery-Åsberg Depression Rating Scale (MADRS). Interestingly 32.3% of those in the diet support group were considered to no longer be depressed as compared with 8% in the social support group. This demonstrated the powerful impact that nutrition can have on depression, and how it may be a helpful consideration alongside psychological and psychiatric treatments.
Other studies have also found a reduced risk of depression associated with nutritious eating styles such as those recommended by public health guidelines and Mediterranean-style diets (18).
The gut-brain axis
More research is emerging about the important role our gut health plays in terms of our overall health. This applies to our brain health and mood as well, especially as the gut and the brain are closely linked.
The gut-brain axis is the name for the connection between our brain and gut, involving the vagus nerve, that passes information in both directions.
Our gut even produces a significant amount of neurotransmitters, including serotonin, but it isn’t currently clear whether these chemical messengers are available for our brain to use (19).
But there are other chemicals that the gut produces that have been seen to impact on the brain. For example, certain short chain fatty acids (SCFAs) created in the gut as a by-product of consuming fibre may play a role in maintaining the blood-brain barrier and might also impact brain cell and memory function (20). But a lot of this research has been carried out in rats and mice rather than humans.
The bacteria in our gut has also been seen to impact brain function, inflammation and mood. The use of a variety of different probiotic supplements (i.e. beneficial gut bacteria) has been linked with improvements in anxiety and depression (21). But studies in this area have been short, and sometimes small, so ongoing research is needed. Fermented foods can also contain probiotics. Some animal studies have found that they may play a role in improving mental health, but research in humans is lacking (22).
There certainly isn’t enough evidence to use probiotics as the only or main treatment for mental health issues, but they might have a role as an add-on to other treatments.
Tips for improving our gut health include:
- Consuming a balanced diet that contains enough energy to fuel the digestive system (i.e. not too low in calories).
- Variety in the diet is key, particularly when it comes to high-fibre plant-based foods like fruit vegetables, grains, beans, pulses, nuts and seeds. In fact eating more than 30 types of plants per week has been linked with a healthier, more diverse gut microbiome (23).
- Include foods that contain omega-3 and polyphenols in your diet, such as oily fish, olive oil, fruit and vegetables (as included in the Mediterranean diet) (24, 25).
- Experiment with fermented foods like kimchi, kombucha, kefir, sauerkraut, tempeh and miso.
- Stay hydrated.
- Prioritise relaxation and stress management (26). Checkout this article for more information on this.
- Movement is important for gut health as it promotes the movement of stools through the digestive system, and has even been seen to promote gut bacteria diversity (27). There’s some evidence that gentle movement that encourages relaxation like yoga may improve gut-related issues such as IBS and constipation (28,29).
- Getting enough good quality sleep has also been linked with a healthy gut microbiome (30).
- Speaking to your doctor if you have any concerns about your gut or bowel health, for example if you experience gut issues or notice blood in your stools.
What we eat can certainly impact our mood and brain health in a number of ways.
Consuming a balanced, gut-friendly, Mediterranean-style diet has been seen to be particularly good for our brain and may even be a useful add-on to treatment options for depression.
But so many factors impact the risk of depression, and diet alone should never be recommended as a sole treatment option.
Please speak to a loved one or your GP if you are struggling with mood issues or depression. See here for information about available services and helplines in the UK.
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