Study Finds Links Between Ultra-Processed Food and Depression

Scientists found that consuming highly processed foods, particularly artificial sweeteners and artificially sweetened drinks, may increase the risk of developing depression.

Ultra-processed foods typically contain preservatives, artificial flavors, and artificial sweeteners. Although convenient and easy to prepare, ultra-processed foods may pose risks to human health. For example, research has linked the consumption of these food products to an increased risk of cancer and type 2 diabetes. In addition, teens who eat high amounts of ultra-processed food may have a higher risk of depressive symptoms.

Still, few studies have looked at the potential links between ultra-processed food and depression.

To investigate this further, researchers from Massachusetts General Hospital and Harvard Medical School in Boston examined the potential associations between ultra-processed food and its components and the incidence of depression.

Their findings were published on September 20 in JAMA Network Open.

The study included 31,712 mostly non-Hispanic white female participants from the Nurses' Health Study II between 2003 and 2017. The participants were 42-62 years old and depression-free at the start of the study.

The scientists assessed each participant's diet using validated food frequency questionnaires (FFQs) every four years. They then estimated ultra-processed food intake via NOVA classification. Using this classification, the researchers were able to group foods by their level of processing, such as sweet snacks, ready-to-eat meals, beverages, and artificial sweeteners.

The team also assessed the incidence of depression using two definitions. These included a strict definition of depression, which requires self-reported clinician–diagnosed depression and regular use of an antidepressant, and a broad definition involving a clinical diagnosis and/or antidepressant use.

Among the participants, those with a higher intake of ultra-processed foods tended to have a higher body mass index (BMI), higher smoking rates, and more health conditions such as high blood pressure and diabetes. They also were less likely to exercise regularly.

After analyzing the data, the team identified 2,122 cases of strict definition depression and 4,840 cases of depression using the broad definition.

After adjusting for a host of factors that could impact the results, including BMI, physical activity, smoking status, overall diet quality, and co-occurring health conditions, the researchers found that participants with the highest intake of ultra-processed foods had an increased risk of broad and strict definition depression compared to those who consumed the lowest number of processed foods.

Specifically, participants with the highest ultra-processed food intake — nine or more servings a day — had a 49% higher risk of strict definition depression than individuals in the low processed food intake group who consumed four servings per day.

High ultra-processed food consumption also increased the risk of broad definition depression by 34%.

However, depression risk was more significantly associated with consuming artificial sweeteners and artificially sweetened beverages.

Still, the scientists also found that participants who reduced their intake of ultra-processed foods by at least three servings daily lowered their risk of depression compared to those who continued to eat the same amounts.

While the study had strengths, including a relatively large sample size and adjustments for factors that could skew the results, the participants were primarily non-Hispanic white females. So, the results might not translate to the general population.

Moreover, people who begin to feel depressed may choose to consume more processed foods rather than healthier alternatives, which might play a role in the associations between ultra-processed food and depression.

However, the scientists say that factors potentially influencing the results — such as age, BMI, physical activity, or smoking — did not change the associations found in the study.

"This study has significant limitations, including its observational approach and use of the NOVA classification system, which has been shown to result in ‎the ‎inconsistent classification of foods," said Robert Rankin, President of the Calorie Control Council, an international association representing the low- and reduced-calorie food and beverage industry, to Healthnews.

Rankin adds, "Association does not equal causation, so any results should be interpreted with caution. Further, the NOVA system notably fails to consider well-established relationships between food groups, nutrients ‎and health outcomes. Low- and no-calorie sweeteners have been continually proven to be safe and they remain an effective tool for weight management, sugar reduction, and blood glucose management."

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