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You are what you eat or so the saying goes. But is it true? A new review published in the Journal of European Neuropsychopharmacology looked at nutritional psychiatry and what the research says about mental health and the food we consume.

“The popular press often provide advice to the general public about recommendations on how to improve one’s mental health by changing what we eat, specific diets, supplements or foods,” study author Suzanne Dickson told us. “We are a group of researchers with much diverse yet collective knowledge on nutrition and brain health. We know when facts are clearly wrong, when they are right and all the shades of grey in between. We wanted to set the record straight and explain in an informed balanced manner, the actual data behind common claims and misconceptions.”

While there is data that shows an association between mental health and nutrition, research is lacking when it comes to causality.

“We addressed many different aspects of nutrition and brain health,” Dickson told us. “For some of these, quite a lot is known and so the evidence pretty much aligned to current theories proposed by scientists. However, for other areas, even scientists are drawn in by assumptions, for example, that eating too much sugar exacerbates symptoms observed in children with Attention Deficit Hyperactivity Disorder (ADHD). Actually, the evidence for this is very slim indeed.”

Current studies on nutrition and mental health have small sample sizes among other problems.

“We wanted to provide an explanation as to why it is difficult for scientists and nutritionists to provide proof that any dietary ingredient or food really does improve brain health,” Dickson told us. “We also wanted to explain likely ways that we can make better progress in the future.”

According to the State Indicator Report on Fruits and Vegetables published by the Centers for Disease Control and Prevention, only 12 per cent of Americans are meeting the daily intake of fruits, and nine per cent for vegetables.

“Ours was a review,” Dickson told us. “We read as much possible literature on the various topics and summarized the key components.”

What’s needed are high-quality, randomized control trials, the gold standard of scientific study, say researchers. A recent randomized control trial found that the Mediterranean diet resulted in a reduction in depression that lasted six months. The diet includes foods such as fruit, vegetables, grains, legumes, fish, nuts, olive oil, and beans.

“It is tough to describe the findings because there are so many different topics in our article, some relating to cognitive function, some to ADHD and others to depression and anxiety disorders,” Dickson said. “Essentially, for most disease areas, nutrition can have beneficial effects but often the effects are marginal and we lack knowledge regarding how the nutritional change could cause the proposed effect on mental health.”

Does obesity affect mental health? According to a study published in the Archives of General Psychiatry, there is an association between depression and obesity. The study found that obese people had a 55 per cent increased risk of developing depression.  

“As scientists, we were surprised at how scarce the evidence is to back dietary advice for mental health,” Dickson told us.”We need to battle on to sort out fact from fiction regarding dietary advice for mental health and this can only be done by rigorous investigation. We need well-controlled clinical studies as well as basic mechanistic studies examining the impact of nutrients on the body, on metabolism and brain.”

Dickson advises that in the meantime, we be kind to our brains by making healthier food choices.

“The effects of diet on mental health are likely real," Dickson told us. "Since most data on nutrition and brain health is provisional, it is important not to follow dietary advice that is not evidence-based.”