Researchers announced on Apr. 26 a new controlled-feeding trial designed to investigate whether the way ultra-processed foods (UPFs) are made, or their ingredients, are responsible for potential health risks. The protocol for this randomized controlled trial was published in the journal Contemporary Clinical Trials.
The study addresses ongoing concerns about UPFs, which have become common in diets around the world. Evidence from previous studies suggests that high consumption of UPFs is linked to higher risks of cancer, cardiovascular disease, diabetes, and mortality. However, scientists remain uncertain whether these risks stem from industrial food processing itself or from poor nutrient profiles such as high levels of saturated fat, added sugar, and sodium.
The research team will conduct a two-by-two factorial randomized controlled trial among healthy adults aged 18–75 years with stable weight and certain health criteria. Participants will be randomly assigned to one of four diets: low UPF/low saturated fat-sugar-sodium (SFSS), low UPF/high SFSS, high UPF/low SFSS, or high UPF/high SFSS for six weeks. Meals will be carefully prepared and matched for calories and macronutrients across groups. High-UPF diets will include commercial products like flavored yogurt and pre-packaged sauces; low-UPF diets will feature more homemade recipes using minimally processed ingredients.
Participants will eat some meals under supervision at a cafeteria while collecting others to consume at home. Throughout the study period they must avoid alcohol, probiotics, artificially sweetened drinks, fiber supplements and natural health products. Researchers will track compliance daily through checklists and assess changes in blood lipids such as LDL cholesterol as well as blood pressure and insulin resistance before and after the intervention.
Secondary outcomes include changes in triglycerides, ApoB-100 protein levels, HDL cholesterol (the "good" cholesterol), additional blood pressure measurements over 24 hours as well as measures of insulin sensitivity and glucose levels. Questionnaires on meal satisfaction and physical activity plus body composition scans are also planned.
According to researchers involved in the project summary statement included with the protocol publication: "In summary, the proposed RCT will help unravel which features of UPFs account for their unfavorable health effects...advancing current knowledge and helping inform policymakers in better incorporating UPFs into future guidelines." They note strengths such as careful control over diet conditions but acknowledge that because all participants receive set calorie amounts designed not to alter body weight during the study period it cannot address whether eating more UPFs leads directly to overeating or weight gain.
