Ultra-processed food (UPF) and artificial sweeteners linked to depression in a new study

Back in July, the World Health Organization (WHO) classified aspartame (found in Diet Coke and in many sugar-free gums) as possibly cancer-causing. No need for huge panic with that one though – the WHO also said aspartame is safe if consumed below a daily limit of 40 mg per kg of a person's body weight.

But, according to a new study, ultra-processed food (UPF), and artificial sweeteners in particular, could also be a factor for depression risk. Researchers used data from a big study on women’s long-term health in the US to find out how.

They looked at the diets and mental health of over 30,000 (mostly) white, middle-aged women over the course of 14 years who didn’t already have depression. Researchers estimated their UPF consumption and what type of foods, from ultra-processed grain foods, sweet and salty snacks, ready-to-eat meals, fats and sauces, ultra-processed dairy, processed meat and drinks and artificial sweeteners.

"There have been several studies which have supported an important role for diet in influencing the risk of depression," said Andrew Chan, a professor of medicine at Harvard Medical School and an author of the study. "However, there have been scant data about what specific elements of diet may mediate that association."

After comparing depression rates by the end of the study against UPFs consumed, they found that those who had at least nine portions of UPFs daily had a 49% increased risk of depression than those who had less than four. Artificial sweeteners and artificially sweetened beverages were especially associated with an increased risk of depression. Results have been adjusted for other depression risk factors.

“The relationship between artificial sweeteners and depression stands out clearly,” said Keith Frayn, emeritus professor of human metabolism at the University of Oxford, in response to the study’s findings. “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.”

But others argue that the link isn’t so obvious. “An important consideration is that a diet based on ready meals and artificially sweetened drinks might indicate a hectic lifestyle or one with shift work. In other words, a fast food diet could be an indirect marker of chronic stress,” said Dr. Paul Keedwell, Consultant Psychiatrist and Fellow of the Royal College of Psychiatrists, adding that prolonged stress “probably remains the main risk factor for depression."