Topline
Eating heavily processed foods—particularly artificial sweeteners and artificially sweetened drinks—could increase the risk of developing depression, according to research published Wednesday in JAMA Network Open, another major downside to the pervasive ingredients that dominate American diets and have already been linked to major problems like cancer, diabetes and obesity.
Ultraprocessed foods could be linked to depression, a study found.
Key Facts
The study, which involved nearly 32,000 middle aged women, assessed the diet of participants through questionnaires every four years from 2003 to 2017 and split them into five groups according to the amount of ultra-processed food they consumed.
While most food is processed to some degree or another, ultra-processed foods like packaged snacks and frozen meals typically contain ingredients that rarely feature in home cooking such as protein isolates, hydrogenated oils, high-fructose corn syrup and chemical additives and they are already linked to a host of health conditions like obesity, cancer and diabetes.
Using two different definitions of depression—a strict version based on the report of a clinical diagnosis and regular antidepressant use and a broader category requiring either a clinical diagnosis or antidepressant use—the researchers assessed whether there was a link between diet and the risk of developing depression, taking into account known or suspected risk factors for depression like physical activity, alcohol and tobacco use, other health issues and age.
There were 2,122 cases of depression under the strict definition and the top fifth of consumers—nine or more servings of ultra-processed food a day—had around around a 50% higher risk of depression compared with women who are the lowest amount of four servings or fewer a day, the researchers found (it was around a third higher for the broader category).
When considering different kinds of ultra-processed foods, the researchers found a particular link between artificial sweeteners and artificially sweetened drinks and depression, with the top fifth of consumers having a 26% and 37% higher risk of depression compared to the bottom fifth, respectively.
Andrew Chan, a professor at Harvard Medical School and one of the study’s authors, told Forbes the findings suggest people, particularly those struggling with mental health. “may wish to limit their intake of ultra-processed foods wherever possible.
Tangent
Depression is a complex condition and scientists do not yet have a complete understanding of the disease or its causes. Evidence suggests multiple different social, biological and psychological factors play a role in depression, including genetics, life events and experiences, physical activity, substance use, the amount of sleep a person gets and other health conditions they may have. Diet is thought to play an important role in the risk of developing depression, though Chan told Forbes there is “scant data about what specific elements of diet” mediate that link. “It is hard to rate the importance of diet relative to other factors since there are many contributors to mental health that are highly individual,” Chan said, adding that the study highlights diet “is as important as other common factors we consider to influence mental health.”
What We Don’t Know
The study’s design means it can only assess whether a link exists between depression and ultra-processed foods, not why it exists. The researchers acknowledged their study was limited in terms of diversity—participants were overwhelmingly white women and all were aged between 42 and 62 years at the start—and Chan said more studies were “definitely” needed in “more diverse populations.”
What To Watch For
Chan said the gut microbiome appears to be playing a role in the researchers’ findings. Recent research has linked the collection of trillions of microbes living within our gut to all sorts of conditions including obesity, diabetes, allergies, inflammatory bowel disease and cognitive impairment and our understanding is beginning to unlock new ways of treating disease by altering the microbiome through methods like fecal transplants. “We know that diet is associated with changes in the gut microbiome and that the gut microbiome plays a role in depression. So we are working on studies connecting the two,” Chan said.
Crucial Quote
Chan told Forbes it can be challenging to figure out whether particular factors influence the risk of depression or not. Rather than a particular diet influencing depression, it could simply be that people with depression tend to eat a certain type of diet. It’s a “classic chicken vs. the egg problem,” Chan said, adding that the research has tried to account for these factors to pin diet down specifically as a contributing factor.
Further Reading
The Link Between Highly Processed Foods and Brain Health (NYT)
Are Bacteria The New Ozempic? Research Finds Promising Gut Microbe That Could Help Fight Obesity (Forbes)
Ultra-processed food raises risk of heart attack and stroke, two studies show (Guardian)