Depressive symptoms in a French cohort
Recent studies have linked unhealthy dietary patterns to increased risks of chronic diseases, including obesity, hypertension, metabolic disorders, and cancer. High consumption of ultra-processed foods (UPFs) also predicts increased risk of chronic diseases. European scientists used data from 26,730 participants in the French NutriNet-Sante cohort to determine if high intakes of ultra-processed foods predicted increased risk of depressive symptoms. The French version of the Center for Epidemiologic Studies Depression Scale evaluated depressive symptoms. The NOVA system classified foods reported on repeated 24-hour food records as ultra-processed food or not. The percent of UPFs in daily diets by weight was classified in quartiles from low (median 7 percent) to high (median 23 percent). As expected, participants in the highest quartile generally had poorer quality diets than participants in the lowest quartile. Over an average follow-up of 5 years and after accounting for multiple confounding factors, compared to participants in the lowest quartile of UPF intake, participants in the highest quartile had a significant 21 percent higher risk of developing depressive symptoms. This increased risk occurred even though the average UPF intake of this cohort was “only” 32 percent of energy intake compared to 53 and 58 percent of energy intake in the UK and US, respectively. More broadly, a poor diet bodes ill for mental health.
Depressive symptoms in a large American cohort
Americans eat a lot of ultra-processed foods. UPSs tend to be less nutritious than non-UPFs. Recent studies have linked high intakes of ultra-processed foods to increased risks of all-cause mortality, cancer, type 2 diabetes, and cardiovascular disease. Would eating lots of UPFs increase Americans' risk of depression? Researchers addressed this question with cross-sectional data from 13,637 participants over age 50 years in three waves of the nationally representative US National Health and Nutrition Examination Survey (2011-2016). Participants who consumed high levels of UPFs tended to have poorer quality overall diets. Compared to participants without depressive symptoms, participants with depressive symptoms tended to be middle-aged, have less education, lower income, have obesity, and live alone. Compared to participants in the lowest quartile of UPF consumption (less than 37 percent of daily calories), participants in the highest quartile (73 or more percent of daily calories) had a significant 34 percent higher odds of having depressive symptoms, after accounting for a host of confounding factors. Interestingly, the link between high levels of UPFs and greater risk of depressive symptoms disappeared for participants who reported being moderately active or active. The take-home message: Limit your intake of UPFs and maintain at least a moderate level of physical activity.
Depression in a Spanish cohort
Eating high amounts of ultra-processed foods (UPFs) predicts higher risk of cardiovascular disease, which is linked to depression. Researchers in Spain used data from 14,907 Spanish university graduates with an average of 37 years in the SUN Study to see if higher levels of UPFs predicted increased risk of depression. UPF intake was evaluated according to the NOVA system using data from a food-frequency questionnaire administered 2 and 10 years after baseline. UPF intake was classified in increasing quartiles (119, 210, 289, and 489 grams per day). Depression was determined by an affirmative answer to the question, Have you ever been diagnosed with depression by a medical doctor? or from regular use of antidepressant medications reported on biennial follow-up surveys. Participants who developed depression during a median follow-up of 10 years tended to have higher intake of UPFs, be unmarried, live alone, eat less fruit, vegetables, and fiber, and have lower adherence to a Mediterranean diet. After adjusting for confounding factors and compared to participants in the lowest quartile of UPF intake, participants in the highest quartile had a significant 33 percent higher risk of developing depression during follow-up. The risk was even higher (47 percent) for participants below the median level of physical activity. UPF intake of more than 400 grams per day (about 14 ounces) predicted no further increase in risk of depression.
Depression in another large American cohort
Recent studies link poor diet and UPF intake to risk of depression. A 2023 study from Harvard used data from 31,712 participants in the Nurses’ Health Study with an average at baseline of 52 years at baseline. Follow-up occurred up to 14 years, and the analyses adjusted for a broad set of confounders. Researchers used a strict (self-reported and clinician diagnosed depression and use of anti-depressant medication) and a broad (clinical diagnosis and/or antidepressant medication use) definition of depression. UPF intake was determined from food-frequency questionnaires administered every 4 years. After grouping UPF intake in quintiles and after adjusting for confounders, participants in the highest three quintiles (3, 4, 5) of UPF intake had significant 20, 22, and 49 percent higher risks of developing depression, respectively, compared to participants in the lowest quintile of UPF intake for the strict definition of depression. For the broad definition, the increased risks were 14, 18, and 34 percent, respectively. Of 10 categories of UPFs, only sweet snacks, other artificial sweeteners, and artificially sweetened beverages showed significant increases in risk of depression.
What to do
Limit your purchase of ultra-processed foods such as chips, ready-to-eat dinners, sweet snacks, and sugar-sweetened drinks. They may taste great, but they don’t support better health.