Nutritional psychiatry

In the field of nutritional psychiatry, there is ongoing research about how different diet patterns influence the development or symptoms of psychiatric conditions, such as depression, anxiety, bipolar disorder, and schizophrenia.^[2] There is also research about how various diets could be potential avenues for treatment of mental health conditions.

In addition, nutrition psychiatry acknowledges the importance of quality diet in relation to improved mood regulation. Research suggests that a quality diet is crucial for developing and maintaining a healthy brain. A healthy diet is generally characterized by a high intake of fruit, vegetables, whole grains, nuts, seeds, fish, and limited processed foods. Conversely, diets in high processed foods, fats and sugars are associated with anxiety and depression.^[1] It is noted that the relationship between diet and mental health is "multi-directional," as people experiencing mental illness may face various barriers that make it difficult to adhere to a balanced diet.^[3]

A state of "chronic low-grade inflammation" has been found to play a role in the development of many diseases that affect the brain, including mental disorders and neurodegenerative disorders.^[4] Thus, the “Mediterranean diet" is a specific dietary pattern of interest for researchers given its anti-inflammatory effects. It emphasizes vegetables, fruits, olive oil, and limited red meat and sugar. In contrast, the "Western diet" is seen as pro-inflammatory and contains more refined sugars, saturated fat, and sodium.^[2][5]

Furthermore, the field recognizes that micronutrient deficiencies, especially those involving essential B vitamins (B12 and folate), can impair cognition and contribute to psychiatric symptoms, including fatigue and depression. This evidence has led to the successful investigation of dietary improvement programs in randomized controlled trials (RCTs). These trials demonstrate that structured nutritional interventions can effectively serve as a valuable treatment to help mitigate symptoms in individuals with moderate to severe depression.^[1]

There are many factors that have been found to contribute to depression. Some of these include inflammation, oxidative stress, and the brain-gut microbiome system.^[6]

A Mediterranean diet has been shown to improve depression.^[7] Vitamin D supplementation and fish oil supplementation are also thought to reduce levels of inflammation. Findings suggest that adding vitamin D and fish oil supplements to an existing treatment for depression could have benefits.^[8] Ultra-processed foods are also associated with depression.^[9]

The gut microbiome has also been shown to influence brain health.^[10] The presence of different species of bacteria in the gut will change depending on type of diet pattern, such as a Western versus a Mediterranean diet.^[11] Studies have shown that "prebiotic, probiotic, or synbiotic treatment" can reduce depressive symptoms.^[2] These treatments can increase the diversity of bacteria in the gut and enhance their survival.^[4]

A Mediterranean diet, along with "more fruits and vegetables, omega-3 fatty acids, 'healthy' dietary patterns, caloric restriction, breakfast consumption, ketogenic diet, broad-spectrum micronutrient supplementation, zinc, magnesium and selenium, probiotics, and a range of phytochemicals" is associated with less anxiety.^[5] Meanwhile, dietary factors associated with increased anxiety include diets high in saturated fats and sugar^[5] as well as consuming a high amount of ultra-processed foods.^[9]

Bipolar disorder and schizophrenia are also associated with inflammation.^[2] While more studies are needed, a Mediterranean diet has been shown to be beneficial in bipolar disorder and in schizophrenia.^[4]

It is possible that bipolar disorder symptoms could also be improved by diet, specifically by omega-3 fatty acids, probiotics, and coenzyme Q supplements. A well-balanced diet overall is protective in bipolar disorder, but further research is required to determine whether a specific supplement regimen should become standard.^[12]

It is also known that modern lifestyle changes have shifted humans away from "traditional dietary patterns," and this may play a role in the development of mental health disorders. Logan and Jacka tell us about an "evolutionary mismatch," stating that diets nowadays have more sodium, saturated fats, and refined sugars. This is in comparison to the "ancestral diets" of humans that was largely plant- and animal-based, with little added fats or sugar.^[13] Nutritional psychiatry can be used to explore the fields of biological and environmental factors that influence the mental health that we face today.