The present invention pertains to a muscle synthesis promoter which exhibits a muscle synthesis promotion action, and with which it is possible to efficiently ingest milk protein. More specifically, the present invention pertains to a muscle synthesis promoter containing, as active ingredients, 0.2-1.2 wt.% of a soybean polysaccharide, 0.1-0.5 wt.% of a HM pectin, 0.01-0.1 wt.% of a fibrous insoluble cellulose, and an acidic liquid composition that contains a milk protein mixture including a casein protein and a whey protein. This muscle synthesis promoter is capable of improving the muscle synthesis promotion effect by preventing the curdling of the milk protein and promoting the absorption of the milk protein in the stomach.本發明為關於一種能夠效率良好地攝取乳蛋白，且達成肌肉合成促進作用之肌肉合成促進劑。更詳細來說，本發明為關於一種肌肉合成促進劑，其係含有酸性液狀組成物作為有效成分，該酸性液狀組成物包含0.2~1.2重量%之大豆多糖類、0.1~0.5重量%之HM果膠、0.01~0.1重量%之纖維狀的不溶性纖維素、以及包含酪蛋白與乳清蛋白之乳蛋白混合物。本發明之肌肉合成促進劑能夠防止胃內乳蛋白的凝乳化，且促進乳蛋白之吸收後，提升肌肉合成促進效果。
