Researchers of this study looked at the relationship between ultra-processed foods and depression. Karen Z Berg, a dietitian who was not involved in the study, gave the following definition of ultra-processed foods:

“Ultra-processed foods, by the NOVA definition, are foods that are made up of manufactured ingredients with the addition of salt, oil, or sugar to make [them] palatable and to help preserve [them]. They usually don’t have any worthwhile nutritional benefits. Some examples include cold packaged snacks like chips or cookies, sodas, packaged pastries, many sweet breakfast cereals, candy, etc.”
— Karen Z Berg

“The highly processed nature of these foods often yields a cheaper product that is more shelf-stable and more palatable than a whole food item. This makes them easy to eat. They are also usually high in calories, fat, salt, and sugar which can lead to weight gain,” she told Medical News Today.

This cohort study included Nurses’ Health Study II participants who did not have depression at baseline. The researchers ultimately included 31,712 participants in their analysis.

The results also highlighted that depression risk may be particularly high based on higher consumption of ultra-processed foods containing artificial sweeteners and artificially sweetened beverages.

Jessie Hulsey, an Atlanta-based registered dietitian and creator of Health Down South, who was not involved in the study, commented on the study’s findings:

“Participants with high UPF intake were found to have greater BMI, higher smoking rates, and an increased prevalence of comorbidities such as diabetes, hypertension, and dyslipidemia. Moreover, they were less likely to engage in regular exercise.”

“Diet plays a pivotal role in both our physical and mental well-being, and a recent study [this study] has shed light on a concerning association between the consumption of ultra-processed foods (UPFs) and mental health. These findings underscore the importance of incorporating whole, unprocessed foods into our diets as a crucial step towards reducing the risk of depression and promoting overall well-being.”
— Jessie Hulsey

This research does have certain limitations. First, it only included women, meaning the results cannot be generalized. In addition, the majority of participants were non-Hispanic and white.

“The cohort under investigation consisted [almost] exclusively of non-Hispanic White women, aged 42 to 62 years, with no inclusion of men or individuals from diverse ethnic backgrounds. This homogeneity in the study population calls for caution when generalizing the findings to broader demographics, as the impact of dietary choices on mental health may vary across different gender and ethnic groups,” Hulsey noted.

“Future research should aim to encompass a more diverse range of participants to ensure the applicability of the findings to a wider population, thus providing a more comprehensive understanding of the relationship between diet and mental well-being,” she added.

The research also relies on certain participant self-reporting, which introduces the possibility of inaccurate data collection. The researchers also note that there’s the possibility of misclassification of the outcome since no one conducted structured clinical interviews.

The results also cannot establish that consuming ultra-processed foods causes depression.

These study results add to growing evidence about the health benefits of limiting ultra-processed food consumption. Past studies have also linked processed foods to increased depression risk in the long term.

“Consuming a diet rich in ultra-processed foods is associated with an increased risk of various health issues, including obesity, heart disease, and diabetes. This is largely attributed to their high levels of unhealthy fats, sugars, sodium, and additives, which can lead to imbalanced nutrition and a range of adverse health outcomes when consumed regularly,” Hulsey noted.

People can take steps to reduce their intake of ultra-processed foods using a number of strategies, including replacing ultra-processed foods with healthier options and opting for smaller portions. People can appropriately consult with doctors and nutrition specialists who can provide further nutritional guidance.

“The best way for people to know they are avoiding ultra-processed foods is by reading food labels. Try to eat whole foods as much as possible (i.e. fruits, vegetables, whole grains, beans, lean meat, etc.) in their natural forms. If you must buy packaged goods, read the ingredients and the food label. Look for whole foods on the ingredient list, and avoid foods that have many additives or processed foods in them.”
— Karen Z Berg

“One effective approach is to prioritize whole, unprocessed foods like fruits, vegetables, whole grains, lean proteins, and legumes in your diet. Planning and preparing meals at home allows for greater control over ingredients and cooking methods, reducing reliance on packaged or fast-food options,” Hulsey added.