Nutritional supplements cannot prevent depression, research says

06 Mar 2019 --- Although supplementation has been put forward as a solid method to improve mood and overall well being, a daily intake of nutritional supplements won’t help stave off the onset of depression, a study published in the Journal of the American Medical Association (JAMA) has shown. Instead, regular lifestyle coaching to help people improve their diets and eating behavior, as well as weight loss, may provide a more effective method for preventing depression, the researchers note. The study used supplements which contained folic acid, vitamin D, omega 3 fish oils, zinc and selenium.

The study coined The MoodFood trial, is the largest randomized clinical trial to study the effects of nutritional strategies on the prevention of major depressive disorder. 

It compared different nutritional and lifestyle strategies that might change mood and wellbeing in overweight people, defined as having a body mass index (BMI) > 25. Over 1,000 overweight or obese participants from the UK, the Netherlands, Germany and Spain who were identified as being at elevated risk for depression – but were not currently depressed – took part in the study. Obesity and depression commonly occur together. Approximately 43 percent of adults with depression are obese, and adults with obesity are at increased risk of experiencing depression.

Participants were tracked for one year. During the study, half of the study group received daily nutritional supplements, while the other half were given a placebo and half of the sample also received a psychological and behavioral therapy designed to help them change their habitual dietary behaviors and patterns. This included learning strategies to cope with low mood, to reduce snacking and to increase the consumption of a healthy Mediterranean style diet.

The study found that the supplements worked no better than the placebos in helping participants prevent depression over one year. Although the behavioral therapy to encourage healthy dietary behavior and improve diet was not effective at preventing depression overall, there was some evidence that it prevented depressive episodes in those participants who attended a recommended number of sessions.

This suggests the food-related behavioral therapy only works if the participants get a sufficient “dose” of therapy and are able to change their diet and habitual dietary behaviors sufficiently.

“We expected to find that changing nutrition would influence depression and thus the null finding overall was surprising. It was also surprising that the rates of depression were not as high as expected in the trial sample, indicating that the sample was not as high risk as anticipated,” Professor Ed Watkin, an expert in Experimental and Applied Clinical Psychology at the University of Exeter, tells NutritionInsight. 

“On the other hand, it is not that surprising that the food-related behavioral activation was only effective at reducing depression when adjusted for those participants who had received a minimum recommended number of therapy sessions. The idea of the intervention was to change eating habits and cope with low mood and we would not expect them to change for those participants who attended zero or only a handful of therapy sessions, because we know that habit change takes some repeated practice to change.”

Following the MoodFood findings, project coordinators Professor Marjolein Visser and Professor Ingeborg Brouwer of the Vrije Universiteit Amsterdam have shared their three conclusions for preventing depressive episodes. 

First, a healthy dietary pattern, typified by 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 developing depression. Second, in people with obesity, weight loss can lead to a reduction in depressive symptoms. Third, current evidence does not support the use of nutritional supplements to prevent depression.

“Because depression is such a common problem, finding effective and widely available ways to prevent depression at a population level is an important goal,” says Watkin. “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.”

Regarding further research, Watkins says that more is needed on people who currently have depression and the role that food-related behavioral activation can have in preventing depression must be investigated.

“It may be particularly helpful to examine this therapy in a sample at higher-risk for depression, such as those with a history of prior depression, because it may have a bigger effect in a higher-risk group. There is also an interest in seeing whether this holistic approach can be helpful in patients with current depression – when we were recruiting for the trial, we had lots of people who suffer from depression wanting to know if working on their diet could help their recovery,” he concludes.

The link between obesity and depression has been investigated in other studies. According to an article published earlier this month, an intervention combining behavioral weight loss treatment and problem-solving therapy with as-needed antidepressant medication for participants with co-occurring obesity and depression improved weight loss and depressive symptoms compared with routine physician care. This article reported on the findings of the RAINBOW trial which included 409 patients with obesity and depression.

Science has also previously linked diet and nutrition to mental health. Last month, a University of Leeds, UK, study found that the daily consumption of fruit and vegetables is not just good for our physical health but can also improve mental wellbeing. The consumption of vitamins C and E were found to be particularly salient for mental health.

The importance of the gut-brain axis is also still being explored with research recently establishing a correlation between depression and a group of neurotransmitter-producing bacteria found in the human gut. Interestingly, an inverse relationship between specific gut bacteria and brain activity in areas connected to depression were identified in the animal study. Published in Nature Microbiology, the findings could lead to the development of bacterial therapeutics for depression, including a growing role for probiotics. 

By Laxmi Haigh