The present invention provides a method for treating osteoporosis in a subject in need of such treatment, including administering orally to the subject an effective amount of an extract product of a Dioscorea species capable of promoting proliferation and differentiation of bone marrow cells in the subject, wherein the Dioscorea species is characterized by a randomly amplified polymorphic DNA (RAPD) fingerprint including 14 DNA bands ranging from 428 bp, 452 bp, 537 bp, 602 bp, 723 bp, 817 bp, 934 bp, 1140 bp, 1242 bp, 1478 bp, 1641 bp, 1904 bp, 2151 bp and 2918 bp, respectively, when genomic DNA of the Dioscorea species is amplified with a primer of SEQ ID NO: 9, and the extract product is prepared by a process including the steps of: (a) extracting a tuber of the Dioscorea species using an alcohol-based solvent in the presence of acetic acid (b) subjecting the resultant product obtained in step (a) to a separating treatment to obtain a soluble fraction and (c) removing solvent from the soluble fraction obtained in step (b) extract fractions of Dioscorea sp.
