The current recommended dietary allowance (RDA) of protein is 0.83 g/kg body weight/day for adults. Yet, a considerable proportion of the population are not consuming adequate protein, with the elderly, and individuals on specific diets such as vegetarians and vegans, at higher risk of suboptimal protein intake. This may be exacerbated by the lack of high-quality protein in the diet. Protein quality may be calculated using the digestible indispensable amino acid score (DIAAS) based on true ileal amino acid digestibility (TIAAD) to determine the true utilization of amino acids in the diet. Consequently, an even greater proportion of individuals fall short of meeting the RDA for protein when DIAAS is taken into consideration. This addresses the need to further refine the current RDA of protein intake that takes into account both the amount and quality of protein, and whether it should be increased to optimal levels for health and function.