Protein is essential to human health, supporting lean mass, anabolic processes and multiple physiological functions(1). Protein adequacy is determined not only by the quantity consumed but also by protein quality, including essential amino acid (AA) composition, digestibility, bioavailability and the capacity of dietary protein to meet human requirements(2). Protein quality therefore reflects the extent to which digestible essential AAs are provided in proportions that align with human requirements, a principle underpinning the Digestible Indispensable Amino Acid Score (DIAAS)(3). Where protein sources provide suboptimal proportions of essential AAs, adequacy may require greater total protein intake or complementary protein sources, potentially increasing surplus AAs requiring catabolism and nitrogen excretion(3). Developing foods with AA profiles better aligned with human requirements may therefore improve protein adequacy without simply increasing total protein intake. Despite its nutritional importance, consumer-facing nutrition information predominantly emphasises protein quantity rather than quality. This distinction is increasingly important given the growing interest in high-protein foods, protein-fortified products and alternative protein sources. This study investigated knowledge and understanding of dietary protein and protein quality and explored sources of nutrition information. Adults (n = 51) completed an online survey assessing self-rated nutrition knowledge, information sources, and objective protein knowledge. Objective understanding was assessed using eight multiple-response questions covering protein functions, requirements, dietary sources, complete proteins, satiety and factors influencing requirements. Participants also described protein quality in an open-ended response scored across five domains: AA composition, essential AA adequacy, digestibility/absorption, utilisation by the body, and source/quality differences, producing a protein-quality understanding score. Associations between objective protein knowledge and qualitative protein-quality understanding were examined using Spearman's rank-order correlation. Most participants rated their nutrition knowledge as Excellent or Good (37.3% each). Academic journals (58.8%), health professionals (51.0%) and university sources (43.1%) were commonly reported information sources, with evidence-based sources more frequently reported by participants with higher self-rated knowledge. Objective protein knowledge was relatively high: 49.0% demonstrated Good and 13.7% Excellent understanding, with 94.1% demonstrating at least Moderate understanding. In contrast, protein-quality understanding was limited. Most participants demonstrated no (12%) or very limited (59%) understanding; 22% demonstrated basic and only 8% moderate or strong understanding. Source comparison/quality differences and essential AA adequacy were particularly poorly understood, with 82% and 75%, respectively, demonstrating no evidence of understanding. Objective protein knowledge was weakly positively correlated with protein-quality understanding but was not statistically significant (ρ = .234, p = 0.098). Despite relatively high general protein knowledge, substantial gaps existed in understanding protein quality. Nutrition education should extend beyond protein quantity to explain essential AA adequacy and how protein sources, combinations and food formulation can better align dietary protein with human requirements.