Can our dietary practices help keep depression at bay?
Previous studies have suggested that people who are overweight or have obesity are also more likely to experience depression, leading researchers to wonder whether making dietary changes could help fend off depression.
In a new study called the MooDFOOD trial, a team from the University of Exeter in the United Kingdom, Vrije Universiteit Amsterdam in the Netherlands, the University of Balearic Islands in Palma de Mallorca, Spain, and the University of Leipzig in Germany decided to find out whether different dietary strategies would have any effect on mental health outcomes in overweight or obese people.
"Because depression is such a common problem, finding effective and widely available ways to prevent depression at a population level is an important goal," notes Prof. Ed Watkins, one of the study authors.
The researchers' findings, which now appear in JAMA, offer some hope that certain dietary interventions could be helpful. However, the overall suggestion is that simply making nutritional changes may not be enough to prevent instances of depression.
Supplements bring no mental health benefits
For the trial, the investigators recruited 1,025 participants who each had a body mass index (BMI) higher than 25, meaning that they were either overweight or had obesity.
The study participants were living in four different countries — the U.K., Germany, the Netherlands, and Spain — and specialist assessments had found them all to be at high risk of developing depression, although none of them had depression at baseline.
The researchers randomly assigned about half of the volunteers to take nutritional supplements, including folic acid, vitamin D, omega-3 fish oils, zinc, and selenium, on a daily basis, while the other half received a placebo.
Half of the participants in the treatment cohort also received psychological and behavioral interventions aiming to help them improve their dietary habits.
After a 1-year follow-up period, the investigators found that taking supplements did not have any protective effect against depression compared with the placebo.
"Diet and nutrition held promise as one means to reach large numbers of people. However, this trial convincingly demonstrates that nutritional supplements do not help to prevent depression," Prof. Watkins explains.
Dietary patterns may play a role
Behavioral therapy to encourage better dietary habits yielded results that were more positive, but not significantly so. This intervention did not perform better than the supplement regimen in keeping depression at bay.
However, attending the full number of sessions that the organizers recommended did seem to prevent some depressive episodes in participants who complied with this advice.
"There was a suggestion that changing food-related behavior and diet may help to prevent depression, but this requires further investigation," Prof. Watkins points out.
MooDFOOD trial coordinators Prof. Marjolein Visser and Prof. Ingeborg Brouwer explain that their project, which is the largest randomized clinical trial of its kind to date, led to three major conclusions:
"First, a healthy dietary pattern, [such as] a Mediterranean style diet high in fruit, vegetables, whole grains, fish, pulses, and olive oil, and low in red meat and full-fat dairy products, may reduce the risk of [...] depression. Second, in people with obesity, weight loss can lead to a reduction in depressive symptoms."
"Third," they add, "current evidence does not support the use of nutritional supplements in order to prevent depression."
Future studies, the team notes, should look further into how dietary patterns influence mental health outcomes and what types of dietary change are most likely to help prevent depression.