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A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED)

Parletta N, Zarnowiecki D, Cho J, Wilson A, Bogomolova S, Villani A, Itsiopoulos C, Niyonsenga T, Blunden S, Meyer B, Segal L, Baune BT, O'Dea K (2019) Nutr Neurosci.  2019 Jul;22(7): 474-487. doi: 10.1080/1028415X.2017.1411320. 

Web URL: Read the full article on here



We investigated whether a Mediterranean-style diet (MedDiet) supplemented with fish oil can improve mental health in adults suffering depression.


Adults with self-reported depression were randomized to receive fortnightly food hampers and MedDiet cooking workshops for 3 months and fish oil supplements for 6 months, or attend social groups fortnightly for 3 months. Assessments at baseline, 3 and 6 months included mental healthquality of life (QoL) and dietary questionnaires, and blood samples for erythrocyte fatty acid analysis.


n = 152 eligible adults aged 18-65 were recruited (n = 95 completed 3-month and n = 85 completed 6-month assessments). At 3 months, the MedDiet group had a higher MedDiet score (t = 3.95, P < 0.01), consumed more vegetables (t = 3.95, P < 0.01), fruit (t = 2.10, P = 0.04), nuts (t = 2.29, P = 0.02), legumes (t = 2.41, P = 0.02) wholegrains (t = 2.63, P = 0.01), and vegetable diversity (t = 3.27, P < 0.01); less unhealthy snacks (t = -2.10, P = 0.04) and red meat/chicken (t = -2.13, P = 0.04).

The MedDiet group had greater reduction in depression (t = -2.24, P = 0.03) and improved mental health QoL scores (t = 2.10, P = 0.04) at 3 months. Improved diet and mental health were sustained at 6 months. Reduced depression was correlated with an increased MedDiet score (r = -0.298, P = 0.01), nuts (r = -0.264, P = 0.01), and vegetable diversity (r = -0.303, P = 0.01).

Other mental health improvements had similar correlations, most notably for increased vegetable diversity and legumes. There were some correlations between increased omega-3, decreased omega-6 and improved mental health.


This is one of the first randomized controlled trials to show that healthy dietary changes are achievable and, supplemented with fish oil, can improve mental health in people with depression.


This clinical trial showed significant reductions in depressive symptoms in patients with clinical depression who received both

  • dietary intervention to help them follow a more 'Mediterranean'type' diet, and
  • supplementation with the long-chain omega-3 fats found in fish and seafood (EPA and DHA)

Supplementation with long-chain Omega-3 alone - and particularly EPA - has already shown benefits for reducing depressive symptoms in patients with clinical-level depression, according to meta-analyses of controlled clinical trials.

Dietary intervention is more difficult to assess in this wasy - but the first randomised controlled trial in this area also showed that adopting a Mediterranean-stlye diet, with professional support, was more effective than a placebo intervention in reducing depressive symptoms.

These findings add to the evidence that dietary and/or nutritional interventions can be an effective treatment option for the managment of depression.

See the associated news article for a summary of this study:

See also:

For further information on diet and depression, see: 

And for more information on Omega-3 and depression