Researchers from the universities of Navarra and Las Palmas de Gran Canaria have demonstrated that the ingestion of trans fatty acids (also known as trans-fats) and saturated fats increase the risk of suffering depression, and that olive oil, on the other hand, may protect against this condition.

The study followed 12,059 SUN Project volunteers over the course of six years; the volunteers had their diet, lifestyle and ailments analyzed at the beginning of the project, over its course and at the end of the project.

At the beginning of the study none of the volunteers suffered from depression, at the end of the study 657 new cases had been detected. Of all these cases, the participants with an elevated consumption of trans-fats “presented up to a 48% increase in the risk of depression when they were compared to participants who did not consume these fats,” said Almudena Sánchez-Villegas, Associate Professor of Preventive Medicine at the University of Las Palmas de Gran Canaria, first author of the article.

In addition, the study demonstrated a dose-response relationship, “whereby the more trans-fats were consumed, the greater the harmful effect they produced in the volunteers,” the expert stated.

Trans fatty acids, often known as trans fats, are solidified (usually vegetable) fats, often found in industrially-produced bakery products and fast food. Previously, they were common in margarine-type spreads, but have largely been eliminated. They are also naturally present in certain whole milk products.

The research team, directed by Miguel Ángel Martínez-González, Professor of Preventive Medicine at the University of Navarra, also analyzed the influence of polyunsaturated fats (abundant in fish and vegetable oils) and of olive oil on the occurrence of depression.

“In fact, we discovered that this type of healthier fats, together with olive oil, are associated with a lower risk of suffering depression,” said Martínez-González.

The research offers new perspective on the theory that the Mediterreanean diet may be partly responsible for the lower incidence of depression in Mediterranean Europe, compared to the north.

Increasing rates of depression may be linked to diet, according to Sánchez Villegas.

“It may be due to radical changes in the sources of fats consumed in Western diets, where we have substituted certain types of beneficial fats — polyunsaturated and monounsaturated in nuts, vegetable oils and fish — for the saturated and trans-fats found in meats, butter and other products such as mass-produced pastries and fast food,” he said.

In addition, the research – published in the online peer-reviewed journal PLoS ONE – has been performed on a population with a low average intake of trans-fats, given that it made up only 0.4% of the total energy ingested by the volunteers.

“Despite this, we observed an increase in the risk of suffering depression of nearly 50%,” said Martínez-González. “On this basis we derive the importance of taking this effect into account in countries like the U.S., where the percentage of energy derived from these fats is around 2.5%.”

Finally, the analysis suggests that depression and cardiovascular disease are influenced in a similar manner by diet, and might share similar mechanisms in their origin.

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