Mediterranean diet may prevent depression

Mechanisms by which adherence decreases incidence of depression not known.

Adherence to the Mediterranean diet may have a protective role in the prevention of depression, new data suggest.

Researchers assessed the effect of adherence to the Mediterranean diet on the incidence of clinical depression in 10,094 initially healthy Spanish participants included in the Seguimiento Universidad de Navarra/University of Navarra Follow-up (SUN) Project. Recruitment for this study is ongoing.

Dietary intake was assessed by a food frequency questionnaire; adherence to the Mediterranean diet was scored in accordance to that previously used in the European Prospective Investigation into Cancer and nutrition study. Participants were classified as having incident depression if they were free of depression and antidepressant medication at baseline and reported a physician-made diagnosis of clinical depression or use of antidepressants at follow-up.

The Mediterranean diet is characterized by moderate intake of alcohol and dairy products; low intake of meat; high intake of legumes, fruit, nuts, cereals, vegetables and fish; and a high ratio of monounsaturated fatty acids to saturated fatty acids.

Depression incidence

After a median follow-up of 4.4 years, the researchers identified 480 new cases of depression (156 in men; 324 in women).

Multiple adjusted depression HRs for the four upper categories of adherence to the diet were: 0.74, 0.66, 0.49 and 0.58 (P<.001). Inverse dose-response relationships were found for fruit and nuts, legumes and the monounsaturated–to–saturated fatty acids ratio.

Adherence to the Mediterranean diet was higher among participants who were men, former smokers, married and older. Participants with higher adherence tended to be physically more active and showed a higher total energy intake.

When the researchers merged the third to fifth quintiles and compared them to the lowest quintile, significant associations were found for some of the beneficial items of the score: HR for fruit and nuts was 0.67, 0.71 for legumes, 0.73 for fish and 0.79 for the monounsaturated–to–saturated fatty acids ratio.

Moderate alcohol consumption yielded an HR of 0.81 — higher intake yielded an HR of 0.94 (95% CI, 0.74-1.18).

The researchers acknowledged an inverse association between adherence to the Mediterranean dietary patterns and risk for clinical depression; however, “the specific mechanisms by which a better adherence to the Mediterranean diet pattern could help to prevent the occurrence of depression are not well known,” they wrote.

“Our findings must be confirmed by additional prospective studies with better control of other potential confounders and also by trials with a more objective and rigorous assessment of the outcome,” they concluded.

Sanchez-Villegas A. Arch Gen Psychiatry. 2009; 66:1090-1098.