Consuming large amounts of ultra-processed food, especially drinks containing artificial sweeteners, is associated with a higher risk of depression, research has found.
Despite extensive data linking ultra-processed food with physical ill health, such as strokes, heart attacks and raised blood pressure, this is the first large study to suggest that consuming ultra-processed foods and drinks, particularly those that include artificial sweeteners, could increase the instance of depression.
Using data from one of the biggest studies of women’s long-term health in the US, researchers at Massachusetts general hospital and Harvard medical school examined the diets and mental health of more than 30,000 primarily white middle-aged women between 2003 and 2017 who did not already have depression.
The authors estimated the overall extent of ultra-processed food intake as well as the type of food, such as ultra-processed grain foods, sweet snacks, ready-to-eat meals, fats and sauces, ultra-processed dairy products, savoury snacks, processed meat, beverages and artificial sweeteners.
They then compared how many women went on to develop depression against their consumption of ultra-processed food. Adjusting for other health, lifestyle and socioeconomic risk factors for depression, the research, published in US journal JAMA Network Open, found that those who consumed nine portions or more of ultra-processed foods a day had a 49% increased risk of depression compared with those who consumed fewer than four portions a day.
In addition, those who reduced their intake of ultra-processed food by at least three servings a day were at lower risk of depression than those with relatively stable intake.
“These findings suggest that greater ultra-processed foods intake, particularly artificial sweeteners and artificially sweetened beverages, is associated with increased risk of depression,” the authors concluded.
“Experimental studies have shown that artificial sweeteners may trigger the transmission of particular signalling molecules in the brain that are important for mood.”
Responding to the findings, Keith Frayn, emeritus professor of human metabolism at the University of Oxford, said: “The relationship between artificial sweeteners and depression stands out clearly. This adds to growing concerns about artificial sweeteners and cardiometabolic health. The link with depression needs confirmation and further research to suggest how it might be brought about.”
Others urged greater caution. Prof David Curtis, an honorary professor at University College London Genetics Institute, said: “The only foodstuffs which [this study] shows are associated with increased risk of depression are artificial sweeteners. Of course, this does not mean that an effect of artificial sweeteners is to increase depression risk – it is just that people with increased risk of developing depression tend to consume larger quantities of artificial sweeteners.”
But the authors disagree. Prof Andrew T Chan, chief of the clinical and translational epidemiology unit at Massachusetts general hospital and co-author of the research, said: “The strength of our study is that we were able to assess diet several years before the onset of depression. This minimises the likelihood that our findings are simply due to individuals with depression being more likely to choose ultra-processed foods.”