Laboratory-Analyzed Nutrient Values Diverge from Database Estimates in Research-Specific Diets (Notably for Protein, Iron, Sodium)

Abstract

Nutrient databases are widely used to calculate the composition of research diets, yet their accuracy relative to laboratory measurements remain uncertain. We compared database-calculated values with laboratory-analyzed energy, protein, fat, and trace mineral concentrations in two controlled 5-day dietary patterns—the Dietary Guidelines for Americans Healthy Eating Pattern (DGA-HEP) and a typical American eating pattern (TAEP)—prepared in independent triplicate and analyzed as technical replicates, using a descriptive approach with a >10% relative-difference threshold. Energy and fat generally agreed between laboratory analyses and database estimates, whereas protein was consistently higher by laboratory analysis (DGA-HEP: +13 ± 2%; TAEP: +25 ± 5%). Trace minerals showed nutrient-specific discrepancies, with sodium systematically higher by laboratory analysis (~+14% to +40% across days) and iron systematically lower (~−15% to −58% across days) for both patterns; other minerals varied by nutrient and day. These results indicate that nutrient databases may over- or underestimate key nutrients depending on category, brand, formulation, and preparation. When precise composition is essential for study design or interpretation, targeted laboratory validation—particularly for protein, sodium, and iron—may be warranted.