Diets and Foods Shown to Improve Depression in Randomized Controlled Trials

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Psychiatry is at an important juncture, with the current drug-focused model having only achieved modest benefits. So, what about using nutritional interventions? Diet may be as important to psychiatry as it is to cardiology. That’s quite the bar. You don’t know if diet can help, until you put it to the test.

For example, the famous Geico study, a multicenter, randomized, controlled trial of a nutrition intervention program in a multiethnic adult population in the corporate setting, looked at reducing depression and anxiety, and improving quality of life. Researchers found that advice to eat a strictly plant-based diet improved indicators of depression, anxiety, and work productivity—specifically, significant improvements in depression, anxiety, fatigue, emotional well-being, daily functioning because of emotional health, improvement in impairments while working because of health, overall work impairments because of health, and non-work related activity impairment because of health, compared with the control group at 18 weeks.

Even just cutting out meat can improve mood. Omnivores were randomly assigned to a control group to consume meat, including fish and poultry, daily, or just the fish, or no meat at all. And compared to the control group, some mood improvements were found in the total meat elimination group within just two weeks.

However, just replacing three servings of meat a week with plant-based meat alternatives was not found sufficient to affect psychological measures. Why not at least a serving a day? Researchers gave people as much red meat as could conscientiously be imposed, given the associated cancer risks.

The problem with all these studies, though, is they were all on people who started out mentally healthy. If nutritional psychiatry is going to be a thing, we need to know if can actually help people with major mental illness. To date, only two trials have put dietary interventions to the test for major depression: the SMILES trial and the HELFIMED trial.

The SMILES trial was the first randomized, controlled trial to explicitly seek to answer the question: If I improve my diet, will my mental health improve? It was a 12-week trial consisting of nutritional consulting sessions delivered by a clinical dietician vs a control group “social support protocol” called befriending. So, instead of seeing the dietician, study participants hung out with someone to talk sports, news, or music, or just play cards or board games, with the intention of keeping them engaged and feeling positive. Befriending aims to control for four factors: time, expectancy, therapeutic alliance, and therapist factors, often used as a control condition for clinical trials of psychotherapy. It’s like placebo therapy.

What were they told to eat? It was a Mediterranean-ish diet with lots of whole grains—five to eight servings a day––lots of vegetables, fruits, nuts every day, olive oil, with restrictions on meat, eggs, sweets, refined cereals, fried foods, fast foods, and sugary drinks. They used the MADRS depression rating scale, which rates 0 to 6 as normal, no depression, 7 to 19 mild depression, and 20 to 34 moderate depression. So, study participants in both the diet and control groups started out, on average, with moderate depression. And after three months of social support, the control group felt better, but still technically moderately depressed, whereas the diet group ended up with only mild depression, on average. If one defines remission as scoring less than 10, that was achieved by 32.3% in the diet group, compared to only 8% in the control group.

The HELFIMED study was a similar Mediterranean-style dietary intervention versus social support for three months. The diet groups successfully consumed more vegetables, fruits, nuts, legumes, whole grains, and a greater diversity of vegetables, while eating fewer unhealthy snacks, and less red meat and less chicken. And they indeed appeared to reap mental health benefits in terms of reduced depression and improved quality of life, which were notably sustained to at least six months. Now, they also supplemented with fish oil, but that is unlikely to have a meaningful antidepressant effect. And indeed, in the study, there was no correlation between increased omega-3 levels and improved depressive symptoms. But improvements in a range of mental health outcomes were significantly correlated with the greater diversity of vegetables and fruits, intake of legumes and nuts, and reduced consumption of unhealthy snacks, takeout, and meat.

Any foods in particular that may be beneficial? In this study, men and women diagnosed with major depression were randomized to receive either about two-thirds of a teaspoon of lemon balm leaf powder or lavender flower powder—both disguised in capsules—or an identical looking capsule filled with a typical dose of Prozac. And, both of the herbs appeared to work as well as the drug. Which group is which? Exactly. Now, what they didn’t have is a placebo group, where people essentially took nothing. But there are placebo-controlled trials of lemon balm, showing it can significantly improve anxiety and depression symptoms.

This trial used lavender flower tea on anxiety and depression in the elderly––the same amount in a teabag, but twice a day. Sadly, the control group didn’t receive anything; so, the reduction in depression and anxiety may have just been a placebo effect. But since it’s cheap, simple, simple, and side-effect free, it might be worth giving lavender flower tea a try.

What about vinegar? Now, this study was about improving mood in healthy adults, but two tablespoons of vinegar diluted in a cup (240 ml) of water twice daily with meals for four weeks appeared to lead to a reduction in self-reported depression scores compared to those randomized to instead take vinegar pills with a 100 times less acetic acid, the presumed active ingredient. And finally, wild blueberries. Adolescents were randomized to about five teaspoons a day of wild blueberry powder, versus a placebo powder matched for sugars and vitamin C, and those getting the blueberries had a significantly greater drop in depression scores. But the difference in anxiety did not reach statistical significance.

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• Sarris J, Logan AC, Akbaraly TN, et al. Nutritional medicine as mainstream in psychiatry. Lancet Psychiatry. 2015;2(3):271-274.
• Agarwal U, Mishra S, Xu J, Levin S, Gonzales J, Barnard ND. A multicenter randomized controlled trial of a nutrition intervention program in a multiethnic adult population in the corporate setting reduces depression and anxiety and improves quality of life: the GEICO study. Am J Health Promot. 2015;29(4):245-254.
• Beezhold BL, Johnston CS. Restriction of meat, fish, and poultry in omnivores improves mood: a pilot randomized controlled trial. Nutr J. 2012;11:9.
• Conner TS, Gillies NA, Worthington A, et al. Effect of moderate red meat intake compared with plant-based meat alternative on psychological well-being: a 10-wk cluster randomized intervention in healthy young adults. Curr Dev Nutr. 2025;9(1):104507.
• Firth J, Marx W, Dash S, et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosom Med. 2019;81(3):265-280.
• Jacka FN, O’Neil A, Opie R, et al. A randomised controlled trial of dietary improvement for adults with major depression (The “smiles” trial). BMC Med. 2017;15(1):23.
• Parletta N, Zarnowiecki D, Cho J, et al. A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (Helfimed). Nutr Neurosci. 2019;22(7):474-487.
• Araj-Khodaei M, Noorbala AA, Yarani R, et al. A double-blind, randomized pilot study for comparison of Melissa officinalis L. and Lavandula angustifolia Mill. with Fluoxetine for the treatment of depression. BMC Complement Med Ther. 2020;20(1):207.
• Ghazizadeh J, Sadigh-Eteghad S, Marx W, et al. The effects of lemon balm (Melissa officinalis L.) on depression and anxiety in clinical trials: A systematic review and meta-analysis. Phytother Res. 2021;35(12):6690-6705.
• Bazrafshan MR, Jokar M, Shokrpour N, Delam H. The effect of lavender herbal tea on the anxiety and depression of the elderly: A randomized clinical trial. Complement Ther Med. 2020;50:102393.
• Johnston CS, Jasbi P, Jin Y, et al. Daily vinegar ingestion improves depression scores and alters the metabolome in healthy adults: a randomized controlled trial. Nutrients. 2021;13(11):4020.
• Fisk J, Khalid S, Reynolds SA, Williams CM. Effect of 4 weeks daily wild blueberry supplementation on symptoms of depression in adolescents. Br J Nutr. 2020;124(2):181-188.

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• blueberries
• dairy
• depression
• fake meat
• fish
• meat
• mental health
• poultry
• vinegar