October 7, 2009 — The sunny mental states of Mediterraneans compared with Northern Europeans might owe as much to the food as to the weather, new research suggests.
Results from a study of more than 10,000 initially healthy Spaniards shows that those who followed the Mediterranean dietary pattern (MDP) — rich in vegetables, fruits, nuts, whole grains, and fish — were less likely to develop depression during the next 4 years than those who ate more meat, meat products, or whole-fat dairy. The study, by lead author Almudena Sánchez-Villegas, BPharm, PhD, and colleagues at the University of Las Palmas de Gran Canaria and Clinic of the University of Navarra, Pamplona, Spain, is published in the October issue of the Archives of General Psychiatry.
"The most important fact is that adherence to an overall healthy dietary pattern might be able to reduce the risk of depression. Our interpretation is that healthier food habits may lead to an improved brain function and consequently to a greater resilience to better face the frustrations of every day, to control stress, and to overcome personality deficits," senior author Miguel Angel Martinez-Gonzalez, MD, PhD, MPH, told Medscape Psychiatry.
Mediterranean Diet Cut Depression Risk by 30%
Dr. Martinez-Gonzalez said the risk for depression was substantially lower in participants with higher adherence to the MDP and that depression rates were about 30% lower in those with the highest consumption of fruit, nuts, legumes, and monounsaturated vs saturated fats.
"The important thing regarding fish is that a very low consumption of fish (lowest quintile) was in fact a risk factor when it was compared with the 3 upper categories of fish consumption (merged together)," he added.
The researchers were trying to determine why the lifetime prevalence of mental disorders is lower in Mediterranean than Northern European countries. One possible factor is diet, as previous research has suggested that the monounsaturated fatty acids in olive oil — used abundantly in the Mediterranean diet — may be associated with a lower risk for severe depressive symptoms.
The study included 10,094 healthy Spanish participants who reported their dietary intake on a food frequency questionnaire. After a median follow-up of 4.4 years, there were 480 new cases of depression. Individuals who followed the Mediterranean diet most closely had a greater than 30% reduction in the risk for depression than whose who had the lowest Mediterranean diet scores. The association did not change when the results were adjusted for other markers of a healthy lifestyle.
The strength of the inverse association between the [MDP] and depression surprised the investigators. "The new question for us is that if these results will be reproduced in a primary prevention trial," Dr. Martinez-Gonzalez said. "Another new question is whether the MDP is longitudinally associated with increased serum levels of BDNF," or brain-derived neurotrophic factor — a peptide critical for axonal growth, neuronal survival, and synaptic plasticity.
According to the authors, "An emerging concept in neuroscience is that perturbations in the health of cerebral endothelium (such as some loss of the neuroprotection afforded by BDNF) may mediate progressive neuronal dysfunction." Depression is associated with low BDNF in some patients.
More Studies Needed in Other Countries, Populations
Viviane Kovess-Masféty, MD, PhD, director of Epidemiology Evaluation, and Public Health at Hôtel Dieu EHESP in Paris told Medscape Psychiatry that this study should be viewed as hypothesis-generating rather than conclusive.
Dr. Kovess-Masféty, who was lead author on a major study of differences in mental health problems in 6 European countries (Psychiatr Serv. 2007;58:213–220) said that limitations of this study include relatively poor measures of depression and a highly selected population; namely, students and professionals in only one country, Spain. "The strongest parts are the diet measures, the sample size and follow-up, plus the discussion on possible pathways for MDP effects," she said.
She also noted that there is no consideration of cultural factors in the analysis. "From a French viewpoint, Spanish people have strong social networks, are a very positive society, and have a strong sense of fiesta and going...out together. In addition, their society is very open to other factors that may reduce suicide rates and proneness to depression, such as family cohesion.
"In my opinion, the paper needs to be replicated in another country — or at least another region — and with control group to be really taken into consideration," she said.
The study was supported by the Spanish Government Instituto de Salud Carlos III, the Fondo de Investigaciones Sanitarias, and the Navarra Regional Government. The authors have disclosed no relevant financial relationships.
Arch Gen Psychiatry. 2009;66:1090–1098. Abstract
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Cite this: Mediterranean Diet May Cut Depression Risk - Medscape - Oct 07, 2009.