By Rick Nauert
September 18, 2015

While most are aware of the cardiovascular benefits of eating a Mediterranean or comparable healthy diet, new research suggests a healthy diet can also prevent the onset of depression.

A wholesome diet includes consumption of appropriate partitions of fruit, vegetables, legumes, nuts, and meats.

Researchers explain that the study is among the first to explore the link between nutrition and mental health. Specifically, investigators assessed the correlation between several healthy dietary patterns and the risk of depression among 15,093 people.

Three diets were compared: the Mediterranean diet, the Pro-vegetarian Dietary Pattern, and Alternative Healthy Eating Index-2010. Participants used a scoring system to measure their adherence to the selected diet, i.e. the higher the dietary score indicated that the participant was eating a healthier diet.

Food items such as meat and sweets (sources of animal fats: saturated and trans fatty acids) were negatively scored, while nuts, fruits, and vegetables (sources of omega-3 fatty acids, vitamins, and minerals respectively) were positively scored.

Lead researcher, Almudena Sanchez-Villegas, says, “We wanted to understand what role nutrition plays in mental health, as we believe certain dietary patterns could protect our minds. These diets are all associated with physical health benefits and now we find that they could have a positive effect on our mental health.”

“The protective role is ascribed to their nutritional properties, where nuts, legumes, fruits, and vegetables (sources of omega-3 fatty acids, vitamins, and minerals) could reduce the risk of depression.”

The study included over 15,000 participants free of depression at the beginning of the study. The participants were former students of the University of Navarra, Spain, and registered professionals from some Spanish provinces and other university graduates. All participants are part of the SUN (Seguimiento Universidad de Navarra) Project, a cohort study started on 21st December 1999.

The cohort has been used to identify dietary and lifestyle determinants of various conditions, including diabetes, obesity, and depression.

Questionnaires to assess dietary intake were completed at the start of the project and again after 10 years. A total of 1,550 participants reported a clinical diagnosis of depression or had used antidepressant drugs after a median follow-up of 8.5 years.

Researchers discovered the Alternative Healthy Eating Index-2010 was associated with the greatest reduction of risk of depression but most of the effect could be explained by its similarity with the Mediterranean Diet.

Therefore, common nutrients and food items such as omega-3 fatty acids, vegetables, fruits, legumes, nuts, and moderate alcohol intake present in both diets may be responsible for the observed reduced risk in depression.

Almudena Sanchez-Villegas says, “A threshold effect may exist. The noticeable difference occurs when participants start to follow a healthier diet. Even a moderate adherence to these healthy dietary patterns was associated with an important reduction in the risk of developing depression.

However, we saw no extra benefit when participants showed high or very high adherence to the diets. So, once the threshold is achieved, the reduced risk plateaus even if participants were stricter with their diets and eating more healthily. This dose-response pattern is compatible with the hypothesis that suboptimal intake of some nutrients (mainly located in low adherence levels) may represent a risk factor for future depression.”

Therefore, poor or low consumption of components associated with a healthy diet may place someone at higher risk for depression.

Researchers admit that a limitation of this study is that results are based on self-reported dietary intake and a self-reported clinical diagnosis of depression.

Experts also agree that more research is needed to predict the role of nutrient intake for neurophysiological requirements and identify whether it is minerals and vitamins or proteins and carbohydrates that cause depression.