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

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.