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Depression is a common mental disorder affecting an estimated 5% of the world population.¹ In the United States, depression and anxiety disorders are common, affecting millions of people of all ages.^2,3 Psychotherapy approaches and medications are standard first-line treatments suggested for clinical depression and general anxiety disorders.⁴ In addition, clinical strategies that include nutrition interventions may have powerful impacts, not only for chronic mental health disorders but also for a patient’s overall mental wellness.

The emerging field of nutritional psychiatry suggests a positive relationship between diet quality and mental health.⁵ Recent research suggests that while nutritional habits, dietary patterns, and diet quality may all effect overall mental wellness, they may also be modifiable risk factors for mental disorders.^6-8 For example, a 2022 meta-analysis of 17 observational studies (n=385,541 total participants) found that greater consumption of ultra-processed foods was cross-sectionally associated with increased odds of depressive and anxiety symptoms (OR:1.53; CI 1.43-1.63).⁸ In contrast, recent systematic reviews have indicated that increased intake of fruits and vegetables may be beneficial for overall mental wellness.^9,10

Mental Wellness: Prevention and Treatment of Disorders

While reducing processed foods and increasing antioxidant-rich fruits and vegetables may help bolster mental wellness, dietary patterns such as regularly scheduled meals may also help prevent mental health issues.^7,11 For clinical treatments, research continues to suggest that foods, nutrients, and overall diet quality have the potential to ease symptoms of mental disorders and improve patient outcomes.^12,13

Bipolar Disorder: Mitochondrial support and omega-3

The pathophysiology of bipolar disorder has not been specified; however, promoting mitochondrial function and enhancing dietary quality may provide therapeutic benefit and alleviate some depressive symptoms.^14-16 A double-blind randomized controlled trial (RCT) with 181 participants with bipolar depression found no difference between groups that were either treated with 2,000 mg/day of N-acetylcysteine (NAC), a potential agent for mitochondrial biogenesis, NAC plus a combination of nutrient agents, or placebo.¹⁷ Yet a sub-study of the RCT assessed diet quality and found that participants with better diet quality reported reduced general depression and bipolar symptoms and had greater clinician-rated improvements, regardless of the experiment treatment received.¹⁵ Further, researchers suggested that the combination treatment that included additional mitochondria-supporting nutrients potentially tempered any adverse effects of pro-inflammatory diets on participants’ reported cognitive function.¹⁵

The American Psychiatric Association recommends omega-3 supplementation as an adjunctive therapy for mood disorders, including bipolar depression, noting potentially greater efficacy with treatments of eicosapentaenoic acid (EPA) alone or EPA and docosahexaenoic acid (DHA) together if EPA dosage levels are higher in the combination.¹⁸ To test efficacy of DHA alone, a recent RCT explored DHA as a monotherapy for bipolar disorder, and although the trial was small, with 31 participants with bipolar disorder and 15 healthy controls, researchers found that after 12 weeks of DHA supplementation (1,250 mg daily) versus a placebo of corn oil, no significant differences between the groups on cognitive functions were reported except for testing of emotional inhibition.¹⁹

Healthy dietary patterns and higher-quality diets have been associated with lower levels of depression and better mental health in children and adults.^10,20-22

 

Depression: Overall Diet quality

Adherence to a Mediterranean-style diet has been associated with a reduction in the risk of developing depression.¹² Improving diet quality has also been investigated as a potential treatment for depression, with promising results. Two smaller RCTs from 2017 found that improving overall diet quality by adhering to a Mediterranean-style diet reduced depression symptoms for study participants.^6,21 In fact, one of the studies included only participants with both major depressive disorder and a diet history that was rated as “poor quality” and found that 32% of participants in the dietary intervention group, which improved their diet quality, achieved a remission of depressive episodes within the three-month intervention period.²¹

A Bidirectional Caveat
The relationship between nutrition and mental health has also been discussed as bidirectional, with dietary choices not only possibly impacting mental wellness but mental health states potentially affecting dietary habits and food choices.^23,24 Specific to depression and anxiety, the role of the gut-brain axis and status of the gut microbiota has recently surfaced as a potential consideration and component for future diet-depression research studies and clinical nutrition interventions.²⁵

Clinical Applications

In functional medicine, personalized nutrition interventions are key components to therapeutic strategies that address chronic mental health issues and a patient’s overall mental wellness. Considering a patient’s lifestyle factors and imbalances helps to identify the root cause of their mental health issue, and tools such as IFM’s nutrition-oriented physical exam help to identify inadequate nutrients. IFM’s modifiable food plans such as the Elimination Diet and the Mitochondrial Food Plan are additional resources used by functional medicine practitioners to enhance cognitive health and address inflammatory concerns.

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