Diet can significantly affect mental health and wellbeing, but many dietary recommendations aren’t backed by solid evidence, finds a new review by European neuroscientists.

“We have found that there is increasing evidence of a link between a poor diet and the worsening of mood disorders, including anxiety and depression,” said lead author Suzanne Dickson, Ph.D., from the University of Gothenburg, Sweden. “However, many common beliefs about the health effects of certain foods are not supported by solid evidence.”

Studies of vitamin B12, for example, consistently link the vitamin to improvements in depression, memory and fatigue, Dickson reported. There is also strong evidence for the Mediterranean diet’s effect on anxiety and depression, she said.

But other dietary advice for mental health is not yet firmly supported by clinical trials, such as the recent recommendations to supplement with vitamin D, Dickson claimed. “[I]t is very difficult to prove that specific diets or specific dietary components contribute to mental health,” she said.

Nutritional psychiatry is a young field, and there is a shortage of hard evidence on how nutrition and mental health are connected in humans, added Andreas Reif, chair of the European College of Neuropsychopharmacology, which produced the study.  “This leaves room for speculation and flawed science,” he said in a statement.

In many cases, clinicians and researchers would do well to move from general population observations to a personalized nutrition approach, Dickson and colleagues concluded, among other observations.

The review is published in the journal Neuropsychopharmacology.