Introduction
Depression and anxiety are the most prevalent mental health conditions worldwide and a major cause of disability. Even those with subclinical symptoms experience significant impacts on their well-being and daily functioning. As a result, new strategies to manage both clinical and subclinical depression and anxiety are necessary.
Recent research has highlighted the connection between nutrition and mental health, with studies showing that healthy diets, particularly Mediterranean dietary patterns—rich in fruits, vegetables, nuts, and legumes—are linked to a reduced risk of depression. However, these findings are complicated by reverse causality; for instance, poor mental health may influence unhealthy food choices, like "comfort foods" during stress or low mood. Additionally, factors like financial and environmental barriers, as well as the appetite-altering effects of psychiatric medications, make it harder for individuals with mental illness to maintain a healthy diet.
Foods and Mood
The consumption of highly refined carbohydrates is linked to increased risks of obesity and diabetes. Carbohydrates are ranked by their glycemic index (GI), which measures how quickly they impact blood sugar levels. Diets with a high glycemic index, consisting of refined carbs and sugars, may also harm mental well-being. Longitudinal research suggests that higher glycemic diets are associated with a greater incidence of depressive symptoms. Clinical studies have supported this, showing that diets with a high glycemic load can lead to depressive symptoms in healthy individuals.
There are plausible mechanisms for how refined carbs may increase the risk of depression and anxiety. For example, rapid changes in blood sugar levels can trigger compensatory hormone releases, such as cortisol and adrenaline, which may influence mood, anxiety, and irritability. Recurrent episodes of hypoglycemia (low blood sugar) have also been linked to mood disorders.
The comorbidity of diabetes and depression could also explain the relationship between high glycemic diets and mental health, as both conditions may share abnormalities like insulin resistance and changes in brain function. Additionally, the inflammatory response triggered by high-glycemic foods may play a role in connecting glycemic diets to depression through immune system activation.
It highlights the connections between diet, immune activation, and mental health, emphasizing the role of inflammation in the relationship between poor diet and depression. Mediterranean diets have been shown to reduce inflammation, whereas high-calorie, saturated-fat-rich meals can trigger immune responses that negatively affect brain health. Mental health conditions, including mood disorders, have been linked to heightened inflammation, suggesting that inflammatory diets (high in trans fats and refined carbohydrates) could increase depression risk.
Conclusion
Research has explored the potential benefits of anti-inflammatory agents in reducing depressive symptoms, with some studies suggesting that certain foods with anti-inflammatory properties, such as omega-3 fatty acids and polyphenols, might prevent or alleviate depressive symptoms. Additionally, emerging research on the gut microbiome—comprising trillions of microorganisms in the gut—suggests a connection between dietary patterns and mental well-being. Diets rich in fibers, polyphenols, and healthy fats may support a beneficial gut microbiome that promotes anti-inflammatory effects, while diets high in processed foods may compromise gut health and contribute to mood disorders. While there is growing evidence supporting the relationship between diet, immune activation, and mental health, further research is needed to establish causal links, particularly in how dietary interventions might help prevent or reduce symptoms of depression. Finally, public health initiatives should focus on promoting healthy diets to improve both mental and physical health.
Reference
Firth J, Gangwisch JE, Borisini A, Wootton RE, Mayer EA. Food and mood: how do diet and nutrition affect mental wellbeing? BMJ. 2020 Jun 29;369:m2382. doi: 10.1136/bmj.m2382. Erratum in: BMJ. 2020 Nov 9;371:m4269. doi: 10.1136/bmj.m4269. PMID: 32601102; PMCID: PMC7322666.