Recent research suggests that adjusting overall diet, rather than taking supplements, may help improve symptoms of depression.
Whole food and whole diet interventions show promise as adjunctive treatments for depression, though more research is still needed.
Key Facts:
- 7 studies with over 49,000 participants found that whole food or whole diet interventions reduced depression symptoms compared to control groups.
- The interventions focused on increasing intake of fruits, vegetables, fish, nuts, seeds, and whole grains while limiting processed foods, refined sugars, and unhealthy fats.
- The effect sizes ranged from small to very large, with the Mediterranean diet showing the greatest benefits in the few studies testing it.
- Possible mechanisms relate to reduced inflammation and oxidative stress, improved gut health, and optimized brain functioning.
- Duration of at least 3 months is likely needed to see significant improvements in depression from dietary changes.
- More rigorous, large-scale studies controlling for confounders are still needed to clarify optimal approaches.
Source: Nutrients 2022
Effect of Diet on Depression & Mood
Depression is a major global health concern, affecting over 260 million people worldwide.
It is debilitating on an individual level and costly to societies.
While medications and psychotherapy help many people, a substantial number do not achieve full remission with standard protocols.
This suggests the need for additional treatment approaches.
Diet may be one lifestyle factor that influences risk for depression.
Epidemiological studies consistently link better diet quality with lower depression rates.
People who eat a Mediterranean-style diet high in fruits, vegetables, whole grains, fish, nuts and healthy oils have a lower risk of becoming depressed.
On the other hand, a typical Western diet high in processed foods, refined grains, sugary products and unhealthy fats correlates with higher depression rates.
The mechanisms behind the diet-depression link likely involve reduced inflammation and oxidative stress, improved gut health and optimized brain functioning from healthy diets.
For example, the antioxidants in fruits, vegetables and nuts combat oxidative stress implicated in depression. The anti-inflammatory omega-3 fats in fish and nuts seem protective as well.
Fiber supports a healthy microbiome, which communicates bidirectionally with the brain.
Key micronutrients like B vitamins, zinc and magnesium enable proper neurological functioning.
While observational studies support the diet-depression connection, clinical trials are needed to determine whether dietary changes can effectively treat existing depression.
Recently, interest has grown in testing whole food and whole dietary approaches, rather than supplements, for mental health applications.
Diet Changes to Treat Depression: Reviewing the Evidence
A systematic review and meta-analysis published in Nutrients examined how whole food and whole diet interventions impact depression treatment.
Unlike previous reviews, this focused solely on food-based approaches, not supplements or multicomponent programs.
It included only randomized controlled trials in generally healthy adults that directly measured dietary intake and used validated depression rating scales.
The researchers searched medical databases for clinical trials meeting these criteria published between 2000-2020.
They identified 7 relevant studies with over 49,000 total participants, mostly middle-aged women.
While sample sizes ranged widely, from 25 to nearly 49,000, most were relatively small pilot studies.
The interventions lasted 10 days to one year, with 10 weeks being the average duration.
Four trials tested Mediterranean-style diets or other healthy dietary patterns.
Three focused on increasing intakes of specific phytochemicals or compounds: polyphenols, flavonoids, and tryptophan.
The control groups either received no intervention or continued their normal diets.
Compliance was monitored through food diaries, recalls, or provision of all meals.
Changes in depressive symptoms were evaluated using scales like the Beck Depression Inventory.
All Studies Reported Antidepressant Effects from Diet Changes
In all 7 clinical trials, participants’ depression scores improved more in the dietary intervention groups compared to controls.
The effect sizes ranged considerably, from small to very large.
The results depended on factors like the study population, specific diet tested, intervention length, depression measure used, and study quality.
Three of the five higher quality trials showed large or very large effects from diet on depression.
In one study, depression scores on the Montgomery-Åsberg Rating Scale dropped significantly more over 12 weeks in the group receiving dietary counseling and following a modified Mediterranean diet compared to social support controls.
The effect size was large.
Another trial providing meals high or low in tryptophan, an amino acid precursor of serotonin, found a very large effect on depression ratings in the high tryptophan condition.
However, this crossover study lasted just 2 weeks per dietary period.
The most persuasive evidence comes from the SMILES trial, the largest and longest intervention.
In this 3-month study, adults with moderate to severe depression were randomized to receive either dietary support and counseling to improve diet quality or social support control.
The dietary support group increased fruit, vegetable, whole grain, and lean protein intake while reducing sweets, processed meats and fried foods.
Depressive symptoms improved significantly more in the dietary support group.
Other smaller trials ranged from neutral to positive effects from interventions emphasizing fruits, vegetables, nuts, whole grains, fish, and plant compounds like polyphenols.
The lone negative trial lasted just 10 days, far shorter than the estimated 3-4 months required for dietary changes to impact depression.
Limitations of Research: Diet Changes for Depression
While promising, this emerging body of research has limitations.
Most studies to date have been small pilot trials.
Large-scale studies in diverse populations are still needed.
Depression assessments varied, making comparisons difficult.
Few trials controlled for potential confounding lifestyle factors like exercise, sleep and alcohol use.
Longer interventions with follow-up periods would better assess sustainability of impacts.
Objectively measuring dietary compliance also remains a challenge.
Future studies should include biomarkers like blood nutrient levels.
Finally, few studies examined potential mechanisms, which will be important for optimizing diets and dietary components for mental health.
Overall Diet Quality Matters More Than Specific Foods
The review found that completely prescribed dietary protocols generated large effects but may lack long-term sustainability.
Allowing some individual preferences while improving overall diet quality is beneficial and more achievable.
Common components of effective interventions were increasing fruits, vegetables, whole grains and lean proteins while limiting sweets, refined grains, processed meats and unhealthy fats.
Though studies on individual foods, nutrients and phytochemicals help illuminate mechanisms, reviews suggest total dietary patterns exert the greatest influence on depression.
A Mediterranean or similar whole food pattern provides broad, synergistic benefits from its mix of bioactive plant compounds, fiber, healthy fats and micronutrients.
Such diets counteract multiple biological pathways implicated in depression risk.
Diet As a Component of Depression Treatment Protocols
For clinicians, the current evidence suggests dietary improvement should be part of a comprehensive depression treatment plan, alongside medications and therapy as needed.
Referral to a dietitian nutritionist is recommended for personalized nutrition counseling and regular follow-up support.
Practically, this involves increasing intakes of vegetables, fruits, whole grains, nuts, seeds, plant oils and lean proteins while reducing sweets, refined grains, heavily processed foods, and high-fat or fried items.
- Seafood intake a few times per week provides anti-inflammatory fats.
- Probiotic foods like yogurt, kefir and fermented veggies support gut and brain health.
- Avoiding alcohol excess and staying well hydrated are also advised.
- For optimal outcomes, interventions likely need to last at least 3 months, with 6 months even better.
- Monitoring with food logs can help identify successes, challenges and adherence issues.
- Biannual nutrition check-ins are recommended even after initial improvements to ensure healthy changes are maintained.
A dietary approach offers a low-risk complement to conventional treatments.
But any nutrition changes should be made cautiously in those needing medications or therapy for severe major depressive disorder, under professional guidance.
Dietary Interventions for Mental Health
While more rigorous controlled trials are still needed, the balance of evidence suggests healthy dietary changes can improve depression, especially when part of a multifactorial treatment plan.
The benefits may rival those of antidepressant medications for some individuals, but with minimal risks or side effects.
Looking ahead, research should better define optimal diet compositions and durations.
It must also determine which populations stand to benefit most.
Integrative medicine providers are beginning to incorporate nutrition and other lifestyle approaches into mental health protocols with promising success.
As a modifiable risk factor, diet represents an empowering way for patients to proactively improve their mental health.
Food-based interventions may soon expand treatment options for the millions still suffering from depression worldwide.
The adage “food for thought” may take on new meaning as cutting-edge research transforms our understanding of nutrition’s role in resilience and recovery.
References
- Study: Depression, is it treatable in adults using dietary interventions? A systematic review of randomized controlled trials
- Authors: Simone O’Neill et al. (2022)
