Nutritional Psychiatry - Diet and Mental Health

Mental health conditions, including depression, anxiety, and chronic stress, are among the leading causes of disability in the UK and worldwide. While talking therapies and medication are important treatments, growing evidence supports the powerful role that nutrition plays in brain health and emotional wellbeing.

Blood Sugar Balance: Fuel for a Stable Mood

The brain is one of the most energy-demanding organs in the body, using around 20% of our daily energy intake. It relies heavily on glucose to function. When blood sugar levels fluctuate, whether due to skipping meals or eating too many refined carbohydrates, it can disrupt mood and concentration.

Low blood sugar (hypoglycaemia) causes the body to release stress hormones like adrenaline and cortisol, which can heighten anxiety and emotional instability. On the other hand, chronically high blood sugar has been associated with an increased risk of depression. For example, a study published in the American Journal of Clinical Nutrition found that women who consumed diets with a higher glycaemic index had a 22% greater risk of depression.

How to keep blood sugar stable:

• Eat regular meals. Going too long without eating can cause blood sugar to drop, leading to fatigue, irritability, and cravings.

• Protein helps slow the release of sugar into the bloodstream. Include a source of protein with each meal and snack, such as eggs, yoghurt, chicken, tofu, lentils or nuts.

• Choose slow-digesting carbohydrates like oats, sweet potatoes, lentils, chickpeas, brown rice, quinoa and non-starchy vegetables, which release energy gradually and help maintain steady glucose levels.

• Limit refined sugars and grains, such as white bread, sugary cereals, sweets, pastries and fizzy drinks, as these cause quick spikes and crashes in blood sugar.

Gut Health and the Gut-Brain Axis

The gut and brain are intimately connected through a complex two-way system known as the gut-brain axis. This system allows constant communication between the central nervous system and the digestive system through the vagus nerve, hormones, and immune responses.

One of the most important aspects of this connection is the gut microbiome, the trillions of microorganisms that live in the intestines. These microbes actively help regulate brain chemistry by producing neurotransmitters such as serotonin, dopamine, and GABA, all of which play a critical role in mood, motivation, and relaxation. In fact, roughly 90 percent of the body’s serotonin is produced in the gut, not the brain.

How to support the gut-brain axis:

• Eat a diverse range of fibre-rich plant foods, aiming for 30 different types per week

• Include fermented foods regularly, such as kefir, sauerkraut, kimchi and natural yoghurt

• Minimise intake of processed foods, artificial sweeteners, and alcohol, which can disrupt microbial balance

• Consider a probiotic supplement that includes clinically studied strains, especially if you have digestive issues, have taken antibiotics recently, or experience chronic stress

Key Nutrients That Support Mental Health

Several nutrients play a vital role in brain function and mood regulation. Deficiencies in any of these may contribute to symptoms such as fatigue, low mood, irritability, or poor concentration.

Omega-3 fatty acids: Omega-3s, especially EPA and DHA, are essential for maintaining the structure of brain cells and reducing inflammation. A 2019 study published in the journal Translational Psychiatry found that omega-3 supplementation, particularly with EPA, significantly improved symptoms of depression. These healthy fats are found in oily fish such as salmon, mackerel, and sardines, flaxseeds, chia seeds, walnuts and algae supplements.

Vitamin B12

Low levels of vitamin B12 have been linked to a higher risk of depression. Deficiencies are quite common, especially in vegetarians, older adults, and people with digestive issues that affect nutrient absorption. Vitamin B12 is mainly found in animal-based foods such as eggs and meat, but it can also be obtained from fortified plant-based milks and other fortified foods, making these important sources for those following a vegetarian or vegan diet.

Magnesium

Magnesium plays a key role in supporting the nervous system and regulating the body’s response to stress. It helps promote relaxation by boosting the activity of GABA, a calming neurotransmitter. A 2017 systematic review published in PLOS ONE found that magnesium supplementation reduced anxiety symptoms in adults, particularly in those who were deficient or experiencing high levels of stress. Good dietary sources of magnesium include pumpkin seeds, spinach, almonds, and whole grains.

Zinc

Zinc is essential for healthy brain function, playing a vital role in brain signalling, neuroplasticity, and the regulation of inflammation. Research has shown that people with depression often have lower levels of zinc. Include zinc-rich foods in the diet, such as shellfish, red meat, nuts, and legumes like chickpeas and lentils.

Vitamin D

In the UK, vitamin D deficiency is common during the winter months due to limited sunlight. A 2013 review published in the British Journal of Psychiatry found that low levels of vitamin D are linked to a significantly increased risk of depression. While small amounts of vitamin D can be obtained from foods such as oily fish, eggs, and fortified products, supplements are often necessary during times of low sun exposure to maintain adequate levels and support mental health.

Mood-Boosting Foods

Certain foods contain nutrients and compounds that have been shown to support emotional wellbeing, either by influencing brain chemistry, reducing inflammation or supporting the gut-brain connection. Including these in your daily diet can offer natural support for a more balanced mood.

• Oily fish: A key source of omega-3s that help reduce inflammation and support healthy brain function

• Dark chocolate: (70 percent or higher) Contains flavonoids, magnesium and compounds that may enhance mood and promote calm

• Pumpkin seeds: High in magnesium and tryptophan, a precursor to serotonin

• Leafy greens: (e.g. spinach, kale, rocket) Packed with folate, which is linked to lower rates of depression

• Fermented foods: (e.g. kefir, kimchi, sauerkraut, natural yoghurt) Support gut health and may help regulate mood via the gut-brain axis

• Berries (e.g. blueberries, strawberries): Rich in antioxidants which help reduce inflammation and oxidative stress in the brain

• Nuts and seeds: (especially walnuts and flaxseeds) Offer healthy fats, zinc and selenium, all linked to better mood regulation

• Eggs: Contain B vitamins, choline and protein, all of which contribute to brain health and neurotransmitter production

Final Thoughts

Mental health is influenced by a combination of biological, psychological, and social factors. While nutrition alone is not a cure, it plays a powerful role in how we feel, think, and cope with stress. If you would like to make changes to support your mood, do feel free to get in touch.

References

1. Gangwisch JE et al. High glycemic index diet as a risk factor for depression. Am J Clin Nutr. 2015;102(2):454–463.

2. Foster JA et al. Stress and the gut-brain axis: regulation by the microbiome. Front Neurosci. 2023;17:1151478.

3. Messaoudi M et al. Psychological effects of a probiotic formulation in healthy volunteers. Gut Microbes. 2011.

4. Li Y et al. Omega-3 fatty acids and depression: meta-analysis. Transl Psychiatry. 2020;10:189.

5. Boyle NB et al. Magnesium supplementation and anxiety. PLOS ONE. 2017;12(6):e0180067.

6. Anglin RE et al. Vitamin D deficiency and depression: meta-analysis. Br J Psychiatry. 2013;202:100–107.

7. Zhang Y et al. 85% dark chocolate improves mood and gut health. Nutrients. 2021.

8. Jenkins TA et al. Mood benefits of tryptophan-rich pumpkin seeds. Int J Tryptophan Res. 2015.

9. Nishida K et al. Probiotic benefits on stress and mood. BMC Microbiome. 2024.

10. Mikkelsen K et al. The role of folate and B12 in mood and cognition. Nutrients. 2016.