Using Recovery Biomarkers to Evaluate Dietary Compliance in Young Adults Provided Controlled Diets High in Ultra-Processed Foods and Free from Ultra-Processed Foods

Abstract

Today, ultra-processed foods (UPFs) make up over half of the daily caloric intake in the United States.1 Ultra-processed foods are manufactured using ingredients that have undergone significant processing and rarely contain entire, unaltered foods.8 Diets high in UPFs have been linked to adverse health outcomes such as overweight, obesity, and increased cardio-metabolic disease risk.14 However, limited experimental research has been done to examine the association between UPFs and these negative health outcomes. This study evaluates dietary compliance in a larger study of young adults consuming controlled diets high in UPFs versus controlled diets free from UPFs. Since participants were free-living while following controlled diets, accurately assessing dietary compliance was essential. Objective dietary assessment methods, such as urinary recovery biomarkers, offer reliable measures of dietary intake.46 As part of a larger controlled feeding trial, this study utilized 24-hour urinary biomarkers such as sodium, potassium, nitrogen (protein), and phosphorus to assess dietary adherence. Participants completed two 14-day controlled diet periods in a randomized order, separated by a four-week washout period. Urinary samples were collected on the second Saturday of each diet period. These samples measured excretion levels of sodium, potassium, nitrogen, and phosphorus. While sodium, potassium, and nitrogen are well-established biomarkers of dietary intake, phosphorus is being investigated as a potential biomarker of UPF consumption due to its prevalence of phosphate food additives in ultra-processed foods. There are currently no established biomarkers of UPF intake, however, some research suggests that urinary and blood biomarkers could potentially be used to assess UPF intake. It is hypothesized that in a healthy population of 18-25-year-olds, urinary sodium, potassium, and nitrogen will accurately reflect dietary intake of sodium, potassium, and protein. If this hypothesis is correct, findings from this study can further validate sodium, potassium, nitrogen, and possibly phosphorus as objective measures of dietary intake and compliance to controlled diets. Additionally, findings may contribute to a growing body of research exploring urinary phosphorus as a potential biomarker for UPF intake.