A healthy diet is a common factor linked to a positive mental outlook. The problem with most of the research in this field though is that it’s hard to tease out which one comes first. Are people in the depths of depression more likely to eat poorly because of their mood? Or does a poor diet exacerbate depressive symptoms?

Australian researchers looked more closely at the effect of diet on mental health. To do this, they used the most powerful type of study: a randomised controlled trial. Sixty-seven people with moderate to severe depression were involved in the 12-week trial.

Those in the treatment group received seven 60-minute sessions of dietary counselling. The control group received a matching social support protocol, but no specific dietary advice. Almost all the participants were receiving another active treatment such as psychotherapy, medications, or both.

The dietary counselling sessions were about getting people to eat more in line with a modified form of the Australian Dietary Guidelines and Dietary Guidelines for Adults in Greece. So there was a distinctly Mediterranean flavour to the advice. Wholegrains, fruits, vegetables, nuts and legumes, and lean meats, chicken, and seafood were on the menu and highly refined starches, sugar and highly processed foods were shunned.

After 12 weeks, there was a statistically significant improvement in the rating scale of depression used (Montgomery-Asberg Depression Rating Scale) in favour of the dietary treatment group. A range of secondary scores looking at mood and wellbeing were all pointing in the positive direction as well. Improvement in depression scores was also related to the degree of adherence to the dietary advice. The benefit of diet on depression was independent of any changes in body weight, self-efficacy, smoking rates or physical activity.

A strength of the study was, including a control group which received an equal level of social support from the research team. The study was small in size, but the adherence and completion rates were very good.

The fact that the dietary intervention group could make significant improvements to their diet quality suggests that dietary improvement is achievable for those with clinical depression despite the fatigue and lack of motivation that are prominent symptoms.

Implications

This is the first randomised-controlled trial to explicitly seek to answer the question: if I improve my diet, will my mental health improve? The results suggest yes, that improving one’s diet in line with current recommendations targeting depression may be a useful and accessible strategy for addressing depression as part of a broader treatment plan.

Last Reviewed: 17/12/2019

© Norman Swan Medical Communications.



References

Jacka FN et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Medicine Epub online January 30, 2017. doi: 10.1186/s12916-017-0791-y.

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