High fruit consumption carries a variety of health benefits. (Larry Crowe/Associated Press)

People who eat a Mediterranean diet rich in fruit, vegetables and cereals may be less likely to develop depression, Spanish researchers have found.

The prevalence of mental disorders is lower in Mediterranean countries than in countries in Northern Europe. Dietary differences, such as use of olive oil, may be the reason, the researchers said.

To find out more, Almudena Sánchez-Villegas and colleagues at the clinic of the University of Navarra, in Pamplona, studied 10,094 healthy Spaniards who filled in questionnaires. Participants were followed for an average of 4½ years.

Those who followed the Mediterranean diet most closely had a more than 30 per cent reduction in risk of depression compared with those who ate diets with the fewest hallmarks of the Mediterranean diet, the team reported in the October issue of Archives of General Psychiatry.

Fruits, nuts, legumes linked

Other factors such as marital status, number of children and factors associated with a healthy diet, as well as personality traits such as anxiety were taken into account.

Over the study period, 480 new cases of depression were identified — 156 in men and 324 in women.

"The specific mechanisms by which a better adherence to the Mediterranean dietary pattern could help to prevent the occurrence of depression are not well known," the study's authors concluded.

They speculated that elements of the diet or the combination of foods may improve blood vessel function, fight inflammation and reduce oxygen-related cell damage to reduce the risk of developing depression.

The Mediterranean diet includes nine features, including:

• A high intake of monounsaturated fatty acids such as olive oil.
• A moderate intake of alcohol and dairy products.
• A low intake of meat.
• A high intake of legumes, fruit and nuts, cereals, vegetables and fish.

In particular, people who ate the most fruits, nuts and legumes showed the lowest risks for depression.

Participants who had a strong adherence to the diet tended to be more physically active, male, former smokers, married and older.

Last year, Dutch researchers suggested depression in older people may be linked to low levels of Vitamin D, which is obtained from sun exposure.