An object of the invention is to provide a safe, novel protein material which when taken daily is effective in the prevention and treatment of osteoporosis, bone fracture, rheumatism, arthritis, and other bone diseases. It is also an object of the invention to provide a bone-strengthening food/beverage or a feeding stuff which when taken by mouth is effective in the prevention and treatment of osteoporosis, bone fracture, rheumatism, arthritis, and other bone diseases. The protein material contains 2 to 15mg/100mg of angiogenin and/or an angiogenin degradation product, and also contains a cystatin and/or a cystatin degradation product in a mass ratio of 0.003 to 0.6 relative to the angiogenin and/or angiogenin degradation product. When ingested, this type of protein material can strengthen bones, and is effective in the prevention and treatment of various bone diseases, particularly osteoporosis, bone fracture, rheumatism and arthritis.本發明之課題為提供安全且藉由日常攝取，對於骨質疏鬆症、骨折、風濕病、關節炎等各種骨疾病之預防、治療為有用之新穎蛋白質素材。又，本發明之課題在於提供藉由經口攝取而對於骨質疏鬆症、骨折、風濕病、關節炎等各種骨疾病之預防、治療為有用的骨骼強化用飲食品或飼料。係一種蛋白質素材，其含有血管生成素(angiogenin)及/或血管生成素分解物2~15mg/100mg，且相對於血管生成素及/或血管生成素分解物，以質量比0.003~0.6之範圍含有胱抑素(cystatin)及/或胱抑素分解物。藉由攝取如此的蛋白質素材，能夠強化骨骼，尤其能夠預防及治療骨質疏鬆症、骨折、風濕病、關節炎等各種骨疾病。
