If you feel a snack attack coming on, do yourself—and your mood—a favor and skip the Twinkies. A new study by researchers at Harvard T.H. Chan School of Public Health shows that ultra-processed foods (especially anything with artificial sweeteners) might increase your risk of depression. That means most of those prepackaged snacks and diet sodas that are easily in reach and widely available may actually be doing more harm to people’s moods than we thought.
The study followed 31,712 mainly white, middle-aged women between 2003 and 2017. The participants filled out a survey every four years to record dietary habits and any new diagnoses or treatments of depression. None of the participants had depression diagnoses prior to the study period.
At the end of the study, the authors compared intake of ultra-processed foods (UPF)—defined as “energy-dense, palatable, and ready-to-eat items” like frozen entrées, processed meat, and sweet or savory snacks—with depression. They found that participants eating nine or more servings of UPFs each day increased their risk of developing depression by 49 percent compared to those eating four or fewer servings. The study further showed that the women who cut back on UPFs by a minimum of three servings a day had a lower risk of depression than participants eating more UPFs. Consuming artificial sweeteners, like those in diet sodas, was linked to a 26 percent increase in the risk of depression in the nine-servings-a-day group compared to the four-a-day group.
The authors of the study do point out that the reason behind the correlation of UPFs and increased depression risk isn’t currently known. Some experimental studies, though, have shown a link between artificial sweeteners and molecules in the brain that affect mood or an altered microbiome in the digestive system.
It’s also important to note this study only focused on white middle-aged women, so the link between diverse populations of women or men’s mental health and ultra-processed foods may not be the same. But it’s probably still a good idea to give that Diet Coke a pass.