Research published in the open access journal BMC Medicine suggests a link between nutrition and mental health.

The study, which analysed the association between depression and dietary patterns in over 15,000 participants found that eating a diet of fruits, vegetables, legumes, nuts and a limited amount of processed meats can prevent the onset of depression.

Three diets were compared – the Mediterranean diet, the Pro-vegetarian Dietary Pattern and Alternative Healthy Eating Index-2010 – and participants used a scoring system to measure their adherence to the selected diet. The higher the score, the healthier the diet of the individual. Items such as meat and sweets were negatively scored, while nuts, fruit and vegetables were positively scored.

All participants were free from depression at the start of the study. A total of 1,550 participants reported a clinical diagnosis of depression or had used antidepressant drugs after a median follow-up of eight and a half years.

Common nutrients and food items such as omega-3 fatty acids, vegetables, fruits, legumes, nuts and moderate alcohol intake found in both the Alternative Healthy Eating Index-2010 and Mediterranean diets were associated with the biggest reduction of risk of depression, with the Alternative Healthy Eating Index-2010 showing the greatest reduction.

Lead researcher, Almudena Sanchez-Villegas from University of Las Palmas de Gran Canaria, 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.”

It was concluded that more research is needed to predict the role of nutrients on mental health and identify whether minerals and vitamins or proteins and carbohydrates cause depression.