The Surprising Connection Between Diet and Mental Health: Scientific Overview by a Dietitian


In recent years, the relationship between what we eat and how we feel has gained significant attention. Research is increasingly showing that our dietary choices can have a profound impact on our mental health and wellbeing. This blog explores the scientific connection between our diet and our mental health, written by me, a registered dietitian and specialist in eating disorders and mental health. We’ll talk about nutrient deficiencies, the Mediterranean diet, gut health, fibre intake, hydration, and more. By the end, you’ll have practical tips to enhance your mental wellbeing through small, manageable changes in your diet. Scroll down to find the tips if you would rather jump ahead.


Nutrient Deficiencies and Mental Health

Nutrient deficiencies can have a direct impact on our brain function and mood. Essential vitamins and minerals like B vitamins, vitamin D, iron, magnesium, and omega-3 fatty acids play crucial roles in maintaining mental health. For instance, low levels of vitamin D have been linked to depression, fatigue and seasonal affective disorder (SAD). Deficiency in folic acid (Vitamin B9) and Vitamin B12, has shown to cause depression, confusion and irritable mood states. Ensuring a balanced diet rich in these nutrients is essential for optimal mental health.


The Mediterranean Diet and Depression: Insights from the SMILES Trial


The Mediterranean diet, known for its emphasis on fruits, vegetables, whole grains, and healthy fats, has been associated with numerous health benefits, including boosting mental wellbeing. The SMILES trial, a pioneering study from Australia, demonstrated that adherence to the principles of the Mediterranean diet significantly reduced symptoms of depression when compared to a control group offered a social support intervention. Participants who followed this diet showed remarkable improvements in their mood compared to those who did not.


Gut Microbiota and Mental Health


Our gut and brain are closely connected through the gut-brain axis via the Vagus nerve.

The gut microbiota, the community of bacteria in our intestines, plays a vital role in this connection. Many researchers actually term it the gut-brain-microbiota axis.

Emerging research suggests that a healthy balance of gut microbiota can positively influence mental health by producingneurotransmitters like serotonin, which regulates mood. In fact, our microbiomes seem to produce the vast majority of the Serotonin in our bodies. About 95%.

Probiotics and prebiotics, found in foods like yogurt, kefir, garlic, and onions, can support a healthy gut microbiota. ‘Psychobiotics’ probiotic supplements engineered to target mental health related microbes are starting to emerge on the supplement market and is a new area being researched.


Fibre Intakes and Mental Health


Dietary fibre is essential for a healthy digestive system, but its benefits extend to mental health as well. Fibre-rich foods like fruits, vegetables, legumes, and whole grains promote the growth of beneficial gut bacteria. Which further support the gut-brain- microbiota connection as discussed above. It is suggested that when following the principles of the Mediterranean diet, a lot of the benefits (such as seen in the SMILEs trial) arise from the resulting increased fibre intake.


Dehydration and Its Impact on Mental Function


Keeping hydrated is crucial for cognitive function and mood. Even mild dehydration (1-2% loss of water in the body) can impair concentration, increase feelings of anxiety, and decrease overall mental performance. Drinking adequate water throughout the day is a simple yet effective way to maintain mental clarity and emotional balance.


Under-Eating and Starvation Symptoms: Lessons from the Minnesota Study


The Minnesota Starvation Study (1944) highlighted the severe psychological effects of under-eating. Participants who were subjected to prolonged calorie restriction experienced depression, anxiety, and obsession with food. These effects are also seen in people who are on diets and to a greater effect in those who chronically diet. I see a lot of chronic dieters in my online clinic to support them to find healthy routines to boost their mental wellbeing.

The Minnesota study underscores the importance of consuming sufficient calories and nutrients to support both physical and mental health. It is important to note that this famous study was incredibly unethical and would not be replicated today.


Disordered Eating, Eating Disorders, and Mental Health


Disordered eating and eating disorders, such as Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder, have profound impacts on mental health. These conditions often lead to severe emotional distress, depression, and anxiety. Working with an eating disorder dietitian can be crucial for individuals struggling with their relationship with food. Helping them develop healthier eating patterns, improve their mental wellbeing and strive for recovery.


The Bidirectional Relationship Between Diet and Mental Health


It’s important to recognise that the relationship between diet and mental health is bidirectional. While our diet can influence our mental health, our mental health can also affect our eating habits. Factors such as trauma, socioeconomic status, and stress levels can impact both what we eat and our mental health. Successfully addressing mental health issues often requires a holistic approach that considers these wider factors.

multidirectional relationship between mental health and diet
multidirectional relationship between mental health and diet


Small Diet Changes to Boost Mental Wellbeing


Making small, manageable changes to your diet can have a significant impact on your mental health. Here are some evidence-based tips to get you started:

  • Stay Hydrated: Aim to drink at least 8 glasses of fluid per day. It doesn’t have to just be water; herbal teas, squash and water-rich fruits and vegetables like cucumber and watermelon can also help.
  • Support Your Gut Health: Take a nutrition approach of adding to your diet, instead of taking away. Include probiotic-rich foods like yogurt, kefir, and sauerkraut, and prebiotic foods like garlic, onions, and bananas in your diet.
  • Get Enough Fibre: Aim for at least 25-30 grams of fibre per day from a variety of sources like fruits, vegetables, legumes, and whole grains.
  • Limit Caffeine and Sugar: Reduce your intake of caffeine and sugary foods and drinks, which can cause anxiety and mood swings in some people.
  • Avoid Diets: As discussed above dietary restriction and disordered eating can have profound effects on your mental wellbeing. Trying to move away from diets and towards healthy routines and habits can support both your mental and physical health.
  • Ensure a diet that meets your micronutrient requirements: if you think you could be at risk of deficiencies, ask your Doctor for a blood test and consider a good quality multivitamin such as Centrum Advance.


Understanding the connection between diet and mental health can help you to make informed choices that support your overall wellbeing. By focusing on nutrient-rich foods, staying hydrated, and supporting your gut health, you can positively influence your mental health and quality of life.

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Blog written by Sophie

Sophie is a Specialist Eating Disorder Dietitian passionate about delivering great quality care and advocating for her clients. She is naturally curious and driven for continued learning both within the profession and outside of it. Sophie founded Mental Health Dietitians in 2024 to be able to work in a way that is value-aligned and makes a difference to the individuals in her care, as well as the wider profession. She currently supports international clients 1-1 in her online clinic.