Future studies into diet and depression should follow the research models used by those investigating how dietary factors affect heart disease risk, say researchers.
Large-scale randomised primary prevention trials that follow the methods and research models used by those who investigate the links between diet and cardiovascular disease (CVD) will help to better elucidate the association between diet and mental health issues such as depression, say Spanish scientists.
Writing in an opinion piece for BMC Medicine, Almudena Sanchez-Villegas and Miguel Martínez-González assess the links between diet and depression, and find it lacking. The duo note that while there is some evidence to suggest an association, and that fast food increases risk of depression – while the Mediterranean diet decreases it - most of these studies do not show causality.
“It is difficult to be sure that the diet is responsible for depression,” explained Sanchez-Villegas. “It could be that depressed people make bad food choices.”
“To address these issues we need long term, randomised clinical studies similar to ones successfully conducted for diet and cardiovascular disease risk,” said Martínez-González. “Only then will we really understand the impact of diet of depression.”
Depression and heart disease
“To date, most of the evidence relating diet to depression is similar to that demonstrating the role that diet plays on MetS or CVD,” argue the researchers. “This is reasonable, because both diseases seem to share several common physiopathological mechanisms.”
“This analogy is supported by the beneficial effects reported for lipids with anti-inflammatory properties, such as omega-3 fatty acids or olive oil.”
Sanchez-Villegas and Martínez-González added that this notion was also backed up by recent research suggesting that consumption of foods rich in trans-fats – such as fast food or commercial bakery products – could contribute to higher depression risk.
“There is an accrual of studies suggesting that depression seems to share common mechanisms with the metabolic syndrome (MetS), obesity and CVD,” they said. “In fact, several major cardiovascular risk factors (including obesity and MetS) are more prevalent among patients who are depressed.”
Follow the CVD model
Sanchez-Villegas and Martínez-González suggest that large randomised prevention trials with interventions based on changes in the overall food pattern and including participants at high risk of mental disorders “could provide the most definitive answer to confirm or refute experimentally the findings reported by observational studies.”
“Though ideal, these trials might not seem feasible,” they said. “However, similar trials have been successfully conducted in cardiovascular fields, as it has been the case for the Dietary Approaches to Stop Hypertension (DASH) diet or the Prevención con Dieta Mediterránea (PREDIMED) trial.”
“Why cannot similar trials be designed for the primary prevention of depression?”
Source: BMC Medicine
Published online ahead of print, doi: 10.1186/1741-7015-11-3
“Diet, a new target to prevent depression?”
Authors: Almudena Sanchez-Villegas and Miguel A Martinez-Gonzalez