We all know that eating a healthy amount of fresh fruit and vegetables and cutting out the processed food is good for the body. Reducing fat and salt while boosting vitamins, protein and fiber helps fend off extra pounds, lower blood pressure and keep the physique in good working order. Now, a new study from Spain appears to confirm what has long been suspected: eating right is good for your mental health, too.
According to the study published in the journal BMC Medicine, eating a Mediterranean-style diet of fruit, vegetables, legumes and nuts, which is low in processed meats, can help prevent the onset of depression. A large study of thousands of people, conducted at the University of Las Palmas de Gran Canaria, suggests depression could be linked to nutrient deficiency. The researchers say this is the first time that a number of different healthy dietary patterns have been analyzed for their association with the risk of depression.
The researchers compared three diets: the Mediterranean diet, the Pro-vegetarian Dietary Pattern and the Alternative Healthy Eating Index-2010. Participants used a scoring system to indicate how much they stuck to each eating plan — the higher the dietary score, the healthier their diet. Foods such as meat and sweets — which are sources of animal fats, saturated fats 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.
"We wanted to understand what role nutrition plays in mental health, as we believe certain dietary patterns could protect our minds," says lead researcher Almudena Sanchez-Villegas. "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 researchers were particularly keen to look at any role omega-3 fatty acids, vitamins and minerals might play in the outcome. "The protective role is ascribed to their nutritional properties, where nuts, legumes, fruits and vegetables…could reduce the risk of depression," says Sanchez-Villegas.
The study looked at data from 15,093 participants who were free of depression at the start of the study — all former students of the University of Navarra, Spain who are registered professionals from some Spanish provinces or university graduates. Questionnaires assigned to assess the dietary intake of each individual were completed at the start of the project and again after 10 years. Overall, 1550 of the participants (or just under 1 in 10) reported having received a clinical diagnosis of depression or that they had had used antidepressant drugs after an intermediate clinical follow-up of 8 and a half years.
The researchers found the Alternative Healthy Eating Index-2010 was associated with the greatest reduction in the risk of depression but that most of the effect could be explained by its similarity with the Mediterranean Diet. Similar foods such as vegetables, fruits, legumes and nuts containing common nutrients (like omega-3 fatty acids) along with moderate alcohol intake were present in both the Alternative Healthy Eating Index-2010 and the Mediterranean diet. This they suggest could be responsible for the apparent reduced risk in depression associated with following the Alternative Healthy Eating Index-2010.
The research seems to suggest that achieving a minimum, rather than a maximum level of change might be the way to approach a healthier diet. "A threshold effect may exist," says Sanchez-Villegas. "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."
One limitation of the study is that the results are based on self-reported dietary intake and a self-reported clinical diagnosis of depression. More research is needed, the team say, to fully understand and predict the impact of nutrient intake on our complex neurophysiological requirements and identify in fine detail just what it is that causes depression. But it starts to look like the biggest benefit can actually be made by the smallest effort. Altering your diet to include plusses like fresh, healthily prepared fruit vegetables while reducing your intake of negatives like "meats and sweets" doesn't have to be all-or-nothing.
The researchers say this makes sense if you consider the body's need for regular, healthy, daily nourishment. "Once the threshold is achieved, says Sanchez-Villegas, "the reduced risk plateaus even if participants were stricter with their diets and eating more healthily." It seems that reaching the goal of a basic healthy level of nutrition — and sticking to it — will, in the short and long run, do you more good than torturing yourself with unsustainable extremes.