The Mediterranean Diet for Brain Health

Dr. David Wiss

January 21, 2022

Mental Health

Of all “diets” that exist, the Mediterranean Diet (“MedDiet”) has the most robust evidence base for healthy aging, due to its measurable impact on physical and mental health. In this article, we focus on recently published literature that demonstrates a Mediterranean style of eating benefits the brain and mental well-being, highlighting some potential mechanisms of action through the gut microbiota and immune system.

The MedDiet is based on traditional foods that people have eaten in countries bordering the Mediterranean Sea, including France, Spain, Greece, and Italy. Components of the MedDiet pattern that appear to have a beneficial role in promoting brain health include:


  • Essential fatty acids (such as omega-3 found in fish) and monounsaturated fatty acids (found in extra virgin olive oil).

  • Polyphenols are found in whole plant foods such as fruits and vegetables.

  • An abundance of vitamins (that occur in the context of whole foods rather than supplements, which have more-than-additive benefits due to food synergy).

  • High fiber (known to improve the presence of beneficial bacteria in the gut).

Proponents of the MedDiet state that it is not technically a “diet” but more so a set of guiding principles, a position with which we at WMN strongly agree. We prefer the term “Mediterranean-style eating” because the word “diet” does not always have positive connotations. Below are the primary tenets of Mediterranean-style eating:


  • Emphasize: fruits, vegetables, whole grains, potatoes, fish/seafood, beans/legumes, nuts, seeds, herbs, spices, avocados, and extra virgin olive oil.

  • Enjoy: poultry, eggs, cheese, and yogurt.

  • Eat less often: red meat, processed meat, sugar-sweetened beverages, added sugars, refined grains, refined oils, and other highly processed foods.

  • Enjoy fruit for dessert.

  • Cook at home and share meals with others.

  • If choosing to consume alcohol, stick with red wine and limit to one glass.

  • Minimize stress levels (don’t count calories or track macros!).

All these components of Mediterranean-style eating reduce oxidative stress, which science is increasingly linking to mental health status [1]. Inflammatory compounds such as interleukin-6, tumor necrosis factor-α, and C-reactive protein have been associated with depressive symptoms, disturbances in neuroendocrine function, leaky gut, monoamine activity, and overall brain function [2]. The hot topic of neuroinflammation might best explain these associations. Another pathway may be through the cortisol response to acute stress, suggesting that specific dietary improvements may increase stress resilience [3]. The MedDiet contains some of the best anti-inflammatory foods to eat, which explains its health benefits. 

Can the antioxidant potential of MedDiet reverse the impact of excess inflammation? One mechanism by which the MedDiet consistently outperforms the Western Diet (eating patterns in the US) is through the interplay between the gut microbiota and the immune system [4]. Fiber-rich plant foods high in polyphenols (such as those in a Mediterranean-style of eating) promote the growth of beneficial bacteria that modulate the immune system to create an anti-inflammatory response. Improvements in beneficial bacteria and immune response might explain the inverse association between the MedDiet and symptoms of anxiety [5–8].

According to a recent systematic review and meta-analysis, the most compelling evidence linking nutrition to mental health was found for MedDiet and incident depression [9]. The MedDiet outperforms the Alternative Healthy Eating Index (AHEI-2010) and the Dietary Approaches to Stop Hypertension (DASH) diet in reducing depressive symptoms [10]. Other studies suggest that greater adherence to the MedDiet is associated with slower cognitive decline and a lower risk of developing Alzheimer’s disease [11].

The highest quality of evidence comes from randomized controlled trials (RCTs), and several of these trials have been conducted using MedDiet. The most compelling reductions in depressive symptoms and improvements in mental health quality of life occurred when MedDiet and fish oil were combined [12]. Other RCTs combining the MedDiet plus the addition of nuts demonstrated a beneficial effect on the risk of depression among patients with Type-2 diabetes [13]. Meanwhile, one RCT did not find evidence of a beneficial effect of a MedDiet intervention on cognitive function among healthy older adults [14], suggesting that the benefits of improving eating patterns may be more pronounced when implemented earlier in the lifespan.

The second highest quality of evidence comes from longitudinal studies, where participants are followed for many years. One prospective study showed that higher adherence to the MedDiet was associated with better cognitive performance (therefore less cognitive decline) in older (70 years old and above) but not middle-aged individuals [15]. These findings highlight that it is never too late to implement dietary changes to improve mental health. 

Other longitudinal results suggest that higher adherence to the MedDiet in midlife was associated with a lower risk of incident depressive symptoms among men but not women [16]. This might be because depressive symptoms are more strongly correlated with women. Other longitudinal findings over an average of over 20 years have shown that higher adherence to the MedDiet was associated with a lower risk of depression later in life among women [17]. 

Taken together, evidence suggests that the MedDiet can benefit people of all ages and genders in most parts of the world. The most substantial findings indicate that a Mediterranean eating style can improve depressive symptoms, and cognitive functioning, and may benefit anxiety symptoms. One mechanism is through improvements in gut microbiota that favor the degradation of fiber-rich foods, produce short-chain fatty acids (such as butyrate), and reduce the inflammatory load [18]. 

Robust evidence links a Mediterranean style of eating to improvements in mental well-being. More research is needed for anxiety, but it is likely that anxiety symptoms can improve from a combination of plant-based food and supplements (e.g., probiotics, and omega-3 fatty acids).

At Wise Mind Nutrition, we are committed to helping you take steps to move toward optimal gut health. A Mediterranean style of eating is one evidence-based path to get you there, but you do not have to stick to the tenets of this approach entirely. Small changes can create momentum toward improving mental well-being and overall quality of life. By eating the best foods for mood disorders, you may not have to worry about how to stop stress eating, because you might begin feeling less stressed!  

References

1. Morris G, Fernandes BS, Puri BK, Walker AJ, Carvalho AF, Berk M. Leaky brain in neurological and psychiatric disorders: Drivers and consequences. Australian New Zealand J Psychiatry. 2018;52(10):924–48.

2. Pano O, Martínez-Lapiscina EH, Sayón-Orea C, Martinez-Gonzalez MA, Martinez JA, Sanchez-Villegas A. Healthy diet, depression and quality of life: A narrative review of biological mechanisms and primary prevention opportunities. World J Psychiatry.

2021;11(11):997–1016. 3. Shively CA, Appt SE, Chen H, Day SM, Frye BM, Shaltout HA, et al. Mediterranean diet, stress resilience, and aging in nonhuman primates. Neurobiology Stress. 2020;13:100254.

4. García-Montero C, Fraile-Martínez O, Gómez-Lahoz AM, Pekarek L, Castellanos AJ, Noguerales-Fraguas F, et al. Nutritional Components in Western Diet Versus Mediterranean Diet at the Gut Microbiota–Immune System Interplay. Implications for Health and Disease. Nutrients. 2021;13(2):699.

5. Sadeghi O, Keshteli AH, Afshar H, Esmaillzadeh A, Adibi P. Adherence to Mediterranean dietary pattern is inversely associated with depression, anxiety and psychological distress. Nutr Neurosci. 2019;1–12.

6. Foster JA. Is Anxiety Associated with the Gut Microbiota? Mod Trends Psychiatry. 2021;32:68–73.

7. Westfall S, Caracci F, Estill M, Frolinger T, Shen L, Pasinetti GM. Chronic Stress-Induced Depression and Anxiety Priming Modulated by Gut-Brain-Axis Immunity. Front Immunol. 2021;12:670500.

8. Gibson-Smith D, Bot M, Brouwer IA, Visser M, Penninx B. Diet quality in persons with and without depressive and anxiety disorders. Journal of Psychiatric Research. 2018;

9. Lassale C, Batty GD, Baghdadli A, Jacka F, Sánchez-Villegas A, Kivimäki M, et al. Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Mol Psychiatr. 2019;24(7):965–86.

10. Nicolaou M, Colpo M, Vermeulen E, Elstgeest LEM, Cabout M, Gibson-Smith D, et al. Association of a priori dietary patterns with depressive symptoms: a harmonised meta-analysis of observational studies. Psychol Med. 2020;50(11):1872–83.

11. Lourida I, Soni M, Thompson-Coon J, Purandare N, Lang IA, Ukoumunne OC, et al. Mediterranean Diet, Cognitive Function, and Dementia. Epidemiology. 2013;24(4):479–89.

12. Parletta N, Zarnowiecki D, Cho J, Wilson A, Bogomolova S, Villani A, 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. 2017;22(7):1–14.

13. Sánchez-Villegas A, Martínez-González MA, Estruch R, Salas-Salvadó J, Corella D, Covas MI, et al. Mediterranean dietary pattern and depression: the PREDIMED randomized trial. Bmc Med. 2013;11(1):208.

14. Knight A, Bryan J, Wilson C, Hodgson J, Davis C, Murphy K. The Mediterranean Diet and Cognitive Function among Healthy Older Adults in a 6-Month Randomised Controlled Trial: The MedLey Study. Nutrients. 2016;8(9):579.

15. Wade AT, Elias MF, Murphy KJ. Adherence to a Mediterranean diet is associated with cognitive function in an older non-Mediterranean sample: findings from the Maine-Syracuse Longitudinal Study. Nutr Neurosci. 2019;1–12.

16. Adjibade M, Assmann KE, Andreeva VA, Lemogne C, Hercberg S, Galan P, et al. Prospective association between adherence to the Mediterranean diet and risk of depressive symptoms in the French SU.VI.MAX cohort. Eur J Nutr. 2017;57(3):1225–35.

17. Yin W, Löf M, Chen R, Hultman CM, Fang F, Sandin S. Mediterranean diet and depression: a population-based cohort study. Int J Behav Nutr Phy. 2021;18(1):153.

18. Filippis FD, Pellegrini N, Vannini L, Jeffery IB, Storia AL, Laghi L, et al. High-level adherence to a Mediterranean diet beneficially impacts the gut microbiota and associated metabolome. Gut. 2015;65(11):1812–21.