A Supplement Dose Is Not a Nutrient Requirement: When the Same Units Answer Different Questions

Abstract

Clinical nutrition guidelines often contain numbers that look directly comparable but answer different questions. A supplement dose, a therapeutic total-intake target, and a population reference intake can all be expressed in grams of the same nutrient, yet they do not represent the same quantity. The risk is not that one number is wrong; it is that the wrong inference is drawn from a number that is right. Using the Nutritional Management Guidelines for Sarcopenia and Frailty 2025 as a current illustration, this commentary distinguishes 3 inferential layers: an implementation regimen, a therapeutic nutrition target, and a dietary reference value. The guideline suggests approximately 20–25 g/day of high-quality protein supplementation with exercise when intake is insufficient, while acknowledging that a recommended total daily protein intake for older people with sarcopenia or frailty cannot yet be specified. These statements are compatible, not contradictory. Moving from a tested regimen to a therapeutic total-intake target requires additional evidence on baseline intake, amount consumed, achieved exposure, comparator exposure, co-interventions, modifiers, and safety. Moving further to a dietary reference value requires a broader evidentiary scope focused on usual intake, intake–response relationships, safety, and population applicability. Guidance should therefore state what each number represents and what additional evidence is required before that number is transferred to a different inferential layer.