Mental health disorders are prominent in today’s society, with the two most common conditions, anxiety and depression, being the leading cause of disability. In an attempt to find new therapeutic approaches to treating mental health conditions, there has been a growing interest in the role of diet and nutrition on mental health. Numerous studies have suggested both the therapeutic and detrimental role of certain diet patterns on mental health disorders. The two most prominent case studies are the therapeutic effects of the Mediterranean diet and the detrimental effects of the Western diet on mental health pathology (Firth, 2020).
The Mediterranean diet consists of high consumption of fruits, vegetables and fatty fish and low consumption of red meat. This diet pattern has been associated with reduced incidence of depression. On the other hand, the Western diet, which consists of high consumption of saturated fats and low consumption of fish, has been shown to have detrimental effects on mental health. In a corroborating study, children who ate more vegetables, fish and fruits, were less likely to have ADHD, whereas consuming fast food and soft drinks was associated with high incidence of ADHD (Clay, 2017). This phenomenon calls to question which nutritional factors in these diets contribute to their effect on mental health (Lachance, 2015).
One potential factor is the effect of carbohydrates on the brain chemistry. Highly glycemic foods (high in carbohydrates) have been associated with depression and have even been shown to induce depressive symptoms in healthy volunteers (Firth, 2020). A possible mechanism for this observed effect is the rapid fluctuations in blood glucose levels. A highly glycemic diet induces a compensatory response, in which blood glucose is lowered to accommodate the high glucose diet. This decrease in blood glucose then triggers the release of several hormones such as cortisol, adrenaline, growth hormone and glucagon, which have been implicated in leading to anxiety and irritability (Firth, 2020). The hormonal fluctuations due to rapid changes in glucose levels may help explain the detrimental effects of Western diet on mental health. However, it is important to note that a highly glycemic diet is also associated with obesity and diabetes, which may affect mental health. Although causality cannot be assumed, the effect of the consumption of carbohydrates on the brain offers a promising mechanism for how food affects mental health.
Another potential factor is the immunostimulatory effect of high calorie meals rich in saturated fats seen in Western diets. Foods high in saturated fats have been shown to stimulate the immune response and induce an inflammatory effect on the body (Lachance, 2015). Such inflammatory effects have been associated with depression. On the other hand, in controlled trials, anti-inflammatory drugs have been shown to decrease depressive symptoms (Firth, 2020). Mediterranean diets typically have anti-inflammatory effects, which may explain the reduced incidence of depression in individuals with the Mediterranean diet.
Additionally, our diet patterns can alter our gut microbiome, or the trillions of bacteria, viruses and archaea that live in our gut, which may have an effect on mental health. The gut microbiome has the ability to interact with and regulate the brain in various ways through neurotransmitters and hormones. Probiotics and certain diet patterns can potentially disturb the equilibrium in the gut microbiome and consequently affect the gut’s regulation of emotion and mood in the brain. For instance, a study found major depressive symptoms were associated with altered gut microbiome (Firth, 2020). Additionally, when fecal gut microbiota from humans with depression were transferred to healthy rodents, it seemed to induce depressive symptoms in the rodents (Firth, 2020). These findings suggest the role of gut microbiome in the regulation of brain pathways and consequently mental health.
Lastly, there are certain nutritional deficiencies in the Western diet that may help explain the difference between Western and Mediterranean diets. Deficiencies in vitamin B12, B9 and zinc have been shown to cause depressive and dementia-like symptoms (Lachance, 2015). These nutrients are believed to be building blocks of numerous essential monoamine neurotransmitters, like serotonin, norepinephrine and dopamine. The reduced synthesis of these neurotransmitters in individuals with Western diets may be a possible reason for the high incidence of mental illness.
Mental health is an ever-growing concern in our society. Despite recent developments in intervention methods, only about one in three patients receive effective treatment (Lassale, 2018). Therefore, it is crucial to look for new, more effective ways to treat individuals with mental health conditions. Although diet by no means can be a replacement for professional help, the recent findings on the relationship between food and mental health point promise the potential for nutrient supplements and dietary changes as a viable intervention method. A healthy diet not only can have therapeutic effects on the brain, but also improves an individual’s general lifestyle and every day functioning. At this point, it is hard to assume that foods have a direct causal effect on mental health. However, further research must be done to establish this intricate relationship.