Abstract
In the not-so-distant past, few people would have strongly linked the words nutrition and psychiatry together. Today, however, nutritional psychiatry is becoming an established field that acknowledges the connection between what we consume—including both food and dietary supplements—and the occurrence of mood disorders. Not surprisingly, it turns out that what we eat may significantly contribute to a healthy brain or an unhealthy brain.
As many other specialties in medicine have already embraced the link between nutrition and health, the field of psychiatry is increasingly joining those ranks. Sarris et al. stated: “Psychiatry is at an important juncture, with the current pharmacologically focused model having achieved modest benefits in addressing the burden of poor mental health worldwide.” 1 They added, “Although the determinants of mental health are complex, the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology.” 1
In a Harvard Health Blog, Eva Selhub, MD, commented: “If your brain is deprived of good-quality nutrition, or if free radicals or damaging inflammatory cells are circulating within the brain's enclosed space, further contributing to brain tissue injury, consequences are to be expected. What's interesting is that for many years, the medical field did not fully acknowledge the connection between mood and food.” 2 She stated, “Like an expensive car, your brain functions best when it gets only premium fuel. Eating high-quality foods that contain lots of vitamins, minerals, and antioxidants nourishes the brain and protects it from oxidative stress—the ‘waste’ (free radicals) produced when the body uses oxygen, which can damage cells.” 2
Research
Mood disorders such as anxiety, depression and bipolar disorder are on the rise, and yet, conventional approaches to treatment such as medication and therapy don't always fully address the problems that people with these disorders suffer from. Emerging research suggests that modifiable approaches such as nutritional therapies may be one way to improve outcomes in these populations.
Marx et al. commented: “There are now consistent mechanistic, observational and interventional data to suggest diet quality may be a modifiable risk factor for mental illness.” 3 Their review provided an overview of the nutritional psychiatry field, including facts about the neurobiological mechanisms modulated by diet and the use of dietary and nutraceutical interventions in psychiatric disorders. The authors stated: “Recent evidence suggests that despite a substantial increase in the use of psychotropics and wider availability of psychotherapies, the population burden of depression has not reduced, and may be increasing. If indeed this is the case, it suggests the presence of operative environmental risk factors for depression.” 3 The authors pointed to recent systematic reviews examining the association between diet and common mental disorders, which have shown healthy dietary patterns to be inversely associated with the probability of, or risk for, depression. They stated that a healthy dietary pattern includes a “high intake of vegetables, fruit, wholegrains, nuts, seeds and fish, with limited processed foods.” Unhealthy diets, which are high in processed, high-fat, high sugar foods, when consumed in adolescence and adulthood are positively associated with depression and anxiety. They added: “Similar evidence exists in early childhood, where poor maternal nutrition status and early-life diet is associated with childhood emotional and behavioral dysregulation.” 3 Of course, it is known that pregnant women must consider what they are eating and drinking while their baby is in the womb, and research suggests that following a healthy diet even before conception leads to the best outcomes.
Utilizing the data from 75,466 participants from the U.K. Biobank, Chen et al. investigated the associations between dietary patterns characterized by energy density, saturated fat, free sugars, and fiber and depressive and anxiety symptoms, with three main dietary patterns. 4 Their findings highlighted “the intricate relationships between overall diet pattern and symptoms of depression and anxiety.” 4 Results of their study showed that “increased consumption of free sugars and saturated fatty acids was associated with a heightened risk of symptoms related to depression and anxiety.” 4 Specifically, results revealed that a dietary pattern characterized by elevated consumption of chocolate and confectionery, butter, high-fat cheese, added sugars, and milk-based desserts, coupled with reduced intake of fresh fruit and vegetables, was associated with higher risks of depressive and anxiety symptoms. The authors pointed out, however, that inconsistent results have been found regarding the effects of specific dietary components in the research literature. They concluded, “Our findings highlight that moderate consumption of foods and beverages may contribute to reducing the current burden of mental disorders at the population level” 4 and called for further research.
Multiple systematic reviews and meta analyses, according to Adan et al., suggest that an increased intake of a healthy diet or a Mediterranean diet decrease the risk of depression. 5 The authors stated that further research is needed regarding the impact of dietary patterns on mental health. They also commented on the impact of nutritional deficiencies on mental health and said that “studies have shown that deficiencies of various nutrients, primarily vitamins, impair cognition. The link is strongest for vitamin B12 (its deficiency causes fatigue, lethargy, depression, poor memory and is associated with mania and psychosis), thiamine (vitamin B1; its deficiency causes beriberi with numbness as CNS symptom and Wernicke's encephalopathy), folic acid (vitamin B9; its deficiency has detrimental effects on neurodevelopment in utero and in infancy; and deficits are associated with a greater risk of depression during adulthood), and niacin (vitamin B3; its deficiency causes Pellagra with dementia as a result).” 5 They called for further research to understand these links.
Jacka et al. conducted a randomized controlled trial design to investigate the effectiveness of a dietary improvement program for the treatment of major depressive episodes. 6 The trial named “SMILES” (Supporting the Modification of lifestyle In Lowered Emotional States) was a 12-week, parallel-group, single blind, randomized controlled trial of an adjunctive dietary intervention in the treatment of moderate to severe depression. The intervention included 67 participants who were randomized to the dietary intervention or control group. The dietary intervention included seven individual nutritional consulting sessions with a clinical dietician. The primary focus of the intervention was on “increasing diet quality by supporting the consumption of the following 12 key food groups (recommended servings in brackets): whole grains (5–8 servings per day); vegetables (6 per day); fruit (3 per day), legumes (3–4 per week); low-fat and unsweetened dairy foods (2–3 per day); raw and unsalted nuts (1 per day); fish (at least 2 per week); lean red meats (3–4 per week), chicken (2–3 per week); eggs (up to 6 per week); and olive oil (3 tablespoons per day), while reducing intake of “extras” foods, such as sweets, refined cereals, fried food, fast food, processed meats and sugary drinks (no more than 3 per week). Red or white wine consumption beyond 2 standard drinks per day and all other alcohol (e.g., spirits, beer) were included within the “extras” food group. Individuals were advised to select red wine preferably and only drink with meals.” 6 The control group intervention was a social support protocol with the same visit schedule and length. The primary endpoints were symptoms of depression and secondary endpoints included remission and change of symptoms, mood, and anxiety. Fifty-five of the participants were utilizing some form or psychotherapy and/or pharmacotherapy. Fifty-six participants had complete data at 12 weeks.
Results showed that, compared with the social support group, the dietary support group demonstrated significantly greater improvement between baseline and 12 weeks on the depression rating scale. Remission was achieved for 32.3% and 8.0% of the intervention and control groups, respectively. The authors concluded “In summary, this is the first RCT to explicitly seek to answer the question: If I improve my diet, will my mental health improve? While emphasizing the preliminary nature of this study and the imperative for replication in studies with larger sample sizes, the results of our study suggest that dietary improvement guided by a clinical dietician may provide an efficacious treatment strategy for the management of this highly prevalent mental disorder. Future work in this new field of nutritional psychiatry research should focus on replication, ensuring larger samples and more sophisticated study designs, in order to confirm effects and afford sensitivity analyses to identify predictors of treatment response.” 6
Mechanism of Action Regarding Dietary Patterns and Mood Disorders
While a clear understanding of the mechanism of action for why following a healthy diet may help improve mood disorders is still emerging, evidence suggests that—just as we see in other medical conditions—inflammation, oxidative stress, factors that alter neurogenesis, and alterations in the gut microbia all play an important role. 3 Adan et al. commented: “Research on diet as a crucial contributing determinant to mental health, while difficult to perform and hard to interpret, is urgently needed. The composition, structure and function of the brain are dependent on the availability of appropriate nutrients, including lipids, amino acids, vitamins and minerals. It is therefore logical that food intake and food quality would have an impact on brain function, which makes diet a modifiable variable to target mental health, mood and cognitive performance. In addition, endogenous gut hormones, neuropeptides, neurotransmitters, and the gut microbiota, are affected directly by the composition of the diet.” 5
Clinical Practice
Emerging evidence suggests that there is an important link between dietary patterns and mood disorders as well as nutritional deficiencies, which may contribute to poor mental health.
Sarris et al. stated, “Evidence is steadily growing for the relation between dietary quality (and potential nutritional deficiencies) and mental health, and for the select use of nutrient-based supplements to address deficiencies, or as monotherapies or augmentation therapies.” 1 The authors commented: “Convincing data suggest that select nutrient-based supplements (in isolation, or in combination), might provide many neurochemical modulatory activities that are beneficial in the management of mental disorders. Examples of these nutrient-based supplements include omega-3 fatty acids, S-adenosyl methionine (SAMe), N-acetyl cysteine (NAC), zinc, B vitamins (including folic acid), and vitamin D. Various clinical investigations support the potential usefulness of omega-3 fatty acids for disorders including, but not limited to, bipolar depression, post-traumatic stress disorder, and major depression, and they are indicated in the prevention of psychosis. Omega-3 fatty acids can provide a range of neurochemical activities via the following mechanisms: modulation of neurotransmitter (noradrenaline, dopamine, and serotonin) re-uptake, degradation, synthesis, and receptor binding; anti-inflammatory and antiapoptotic effects; and the enhancement of cell membrane fluidity and neurogenesis via upregulation of brain-derived neurotrophic factor (BDNF).” 1
Clinicians should consider referring patients with mental health disorders to clinical nutritionists/dieticians who are particularly familiar with the emerging psychiatric literature.
Conclusion
It makes sense that what is good for the body is good for the brain, and it turns out that healthy nutrition should be a part of a clinician's treatment plan for people with mood disorders. The necessary and emerging field of nutritional psychiatry is bringing these issues to the forefront of medicine. Adan et al. stated: “Accumulating evidence provides support for the existence of direct relationships between nutrition, stress susceptibility, mental health and mental function throughout the lifespan. However, the evidence is correlational, and there is a gap in understanding how these effects come about.” 5 The authors added, “The promotion of dietary habits that lead to better mental health, and the identification and validation of critical individual nutritional components, will improve sustainability in our healthcare systems and reduce the economic costs associated with poor mental health and cognitive decline.” 5 ▪