Adequate protein intake is essential for the maintenance of whole-body protein mass. Different methodological approaches are used to substantiate the evidence for the current protein recommendation, and it is continuously debated whether older adults require more protein to counteract the age-dependent loss of muscle mass, sarcopenia. Thus, the purpose of this critical narrative review is to outline and discuss differences in the approaches and methodologies assessing the protein requirements and hence, resulting in controversies in current protein recommendations for healthy older adults. Through a literature search, this narrative review first summarizes the historical development of the FAO/WHO/UNU setting of protein requirements and recommendations for healthy older adults. Hereafter, we describe the various types of studies (epidemiological studies and protein turnover kinetic measurements) and applied methodological approaches founding the basis and the different recommendations with focus on healthy older adults. Finally, we discuss important factors to be considered in future studies to create evidence for international agreement on protein requirements and recommendations for healthy older adults. We conclude by proposing future directions to determine "true" protein requirement and recommendation for healthy older adults.