A glass of wine a day may keep the blues at bay, according to a Spanish study of the benefits of the Mediterranean diet.

The research, part of the broader Predimed report on the Mediterranean diet, followed 5,500 light to moderate drinkers of both sexes over a period of seven years and found that those who drank two to seven glasses of wine a week were less prone to depression than non-drinkers. The findings, published in BMC Medicine, remained significant even when other factors such as smoking, diet and marital status were taken into account. The results were the same for men and women.

"The results show an inverse association between low to moderate alcohol consumption and new cases of depression," said lead researcher Miguel Ángel Martínez-González of the University of Navarra. None of the participants had suffered from depression or alcohol-related problems at the start of the study. Wine was the most popular drink among those studied, who were aged from 55 to 80, an age group in which the risk of depression is relatively high.

"Depression and heart disease seem to share some common mechanisms because they share many similar protective factors and risk factors," Martínez-González said. However, he added that depression prevention was not a reason to start drinking.

"If you are not a drinker, please don't start drinking," he said. "If you drink alcohol, please keep it in the range of one or less drinks a day and consider drinking wine instead of other alcoholic beverages."

The so-called Mediterranean diet – olive oil, wine, a high intake of fruit, vegetables and fish, and a small quantity of dairy and meat products – has been shown to reduce the risk of cardio-vascular disease by up to 30%. However, despite its well-publicised health benefits, it is rapidly being replaced by an international diet of pizza, burgers and fries.

Obesity in Spain is above the OECD average, especially among children, with one in three 13- to 14-year-olds classed as overweight.