Diet and Depression

By Janet Settle MD

In this post, I review A longitudinal analysis of diet quality scores and the risk of incident depression in the SUN Project written by Almudena Sanchez-Villegas et al and published in BMC Medicine on Sept 17, 2015.

Sánchez-Villegas et al. BMC Medicine (2015) 13:197 DOI 10.1186/s12916-015-0428-y

Summary: This study “compares the association of three diet quality scores with depression independent of their micro/macronutrient composition.”

This Spanish cohort (SUN) study followed 15,093 non-depressed former college students for a median 8.5 years to assess the association between dietary patterns (no dietary instructions were given) and risk of developing major depressive disorder.  Self-reported dietary patterns were plugged into three different validated food frequency scales to assess dietary patterns. Participants were assigned to quintiles from lowest to highest scores for each dietary pattern. Depression outcome (n=1051) was measured by self report of physician diagnosis or antidepressant use.

	MDS Mediterranean Diet Score	PDP Pro-vegetarian Dietary Pattern	AHEI-2010 Alternative Heath Eating Index-2010
Score is raised by consumption of:	vegetables fruits nuts legumes cereals fish/seafood moderate alcohol	vegetables fruits nuts legumes cereals olive oil potatoes	vegetables fruits nuts legumes whole grain bread long chain omega-3 polyunsat fats
Score is lowered by consumption of:	meat dairy products	meat dairy products animal fats eggs fish	red/processed meat sugar sweetened drinks fruit juice trans fat excess alcohol excess sodium
Hazard ratio for new onset depression in highest quintile v. lowest quintile of dietary scores (95% CI)	0.84	0.74	0.60

The biggest reduction in depression risk occurs between the lowest (1st quintile) and moderate (3rd quintile) dietary scores with not much additional benefit gained by those in the top two quintiles. This ‘threshold effect’ may represent nutrient deficiencies (possibly in vitamin E, folate, magnesium and zinc which may be related to depression risk) in the low quality diet groups.

The authors conclude “The results of this study suggest that moderate or high (3rd quintile and above) adherence to diet quality scores such as the MDS, the PDP or the AHEI-2010 could be effective for the reduction of depression risk.”

Comments: Long-term dietary studies are difficult. This one corroborates and expands on the findings of a series of recent studies. This group reported on the same cohort (SUN) in 2012, reporting a 36% increased risk of depression in the highest quintile of fast food consumption v. lowest. In the Whitehall II study (2013), women (but not men) who maintained the highest scores on the AHEI scale for diet quality over 10 years, had a 65% reduction in risk of depression.

The brain and body need nutrition to maintain positive mental health. This study confirms what we intuitively expect which is that poor diet is a risk factor for depression. Studies looking at depression risk and individual nutrients have been mixed. This study supports using food as medicine and recommending a diet including and emphasizing vegetables, fruits, nuts, legumes and healthy fats.

I like this study because it supports the idea that a variety of dietary patterns can have a significant impact on depression risk. People get lost in the weeds with arguments about Paleo vs. Mediterranean vs. vegan/vegetarian. The big lever is to reduce sugar and add plant-based foods and healthy fats. Within these parameters, there is leeway for individuals to follow their individual preferences and tastes.

Akbaraly TN, et al. Adherence to healthy dietary guidelines and future depressive symptoms: evidence for sex differentials in the Whitehall II study. Am J Clin Nutr. 2013;97:419–27.

Akbaraly TN, et al. Dietary pattern and depressive symptoms in middle age. Br J Psychiatry. 2009;195:408–13.

Jacka FN, et al. Dietary patterns and depressive symptoms over time: examining the relationships with socioeconomic position, health behaviours and cardiovascular risk. PLoS One. 2014;9, e87657.

Lai J, et al. A systematic review and meta-analysis of dietary patterns and depression in community-dwelling adults. Am J Clin Nutr. 2014;99:181–97.

Rienks J, Dobson AJ, Mishra GD. Mediterranean dietary pattern and prevalence and incidence of depressive symptoms in mid-aged women: results from a large community-based prospective study. Eur J Clin Nutr. 2013;67:75–82.

Ruusunen A, et al. Dietary patterns are associated with the prevalence of elevated depressive symptoms and the risk of getting a hospital discharge diagnosis of depression in middle-aged or older Finnish men. J Affect Disord. 2014;159:1–6.

Sánchez-Villegas A, et al. Association of the Mediterranean dietary pattern with the incidence of depression: the Seguimiento Universidad de Navarra/University of Navarra follow-up (SUN) cohort. Arch Gen Psychiatry. 2009;66:1090–8.

Sánchez-Villegas A, Toledo E, de Irala J, Ruiz-Canela M, Pla-Vidal J, Martínez-González MA. Fast-food and commercial baked goods consumption and the risk of depression. Public Health Nutr. 2012;15:424–32.