The present invention relates to a composition for promoting differentiation of muscle cells containing an amino acid, more specifically, a composition for promoting differentiation of muscle cells comprising phenylalanine and methionine, a pharmaceutical composition for preventing or treating senile muscle loss containing the same, and The present invention relates to a health functional food composition for preventing or improving senile muscle loss. The composition for promoting the differentiation of muscle cells of the present invention and the pharmaceutical composition or health functional food composition containing the composition promotes the differentiation of myoblasts into muscle cells to prevent or improve muscle loss or muscle loss. In particular, it is effective for senile muscle loss, and has the effect of increasing the basal metabolic rate due to the increase in the number of muscle cells and oxidizing fatty acids in the body. [Selection] Figure 1本発明はアミノ酸を含有する筋細胞分化促進用組成物に関し、より具体的には、フェニルアラニン及びメチオニンからなる筋細胞分化促進剤と、これを含有する老人性筋損失予防または治療用薬学組成物及び老人性筋損失予防または改善用健康機能食品組成物に関する。本発明の筋細胞分化促進用組成物及びこれを含む薬学組成物または健康機能食品組成物は、筋芽細胞が筋肉細胞に分化されることを促進して筋肉減少症や筋損失を予防、改善及び治療することができ、特に老人性筋損失に効果的であり、筋細胞数の増加により基礎代謝量が増加して体内脂肪酸を酸化させるという効果を奏する。【選択図】図１
