Alveolar bone resorption, periodontal membrane loss, and gingival recession can be inhibited by administering 500 mg to 2000 mg per day of calcium, 10 mg to 40 mg per day of soy isoflavone aglycone, and vitamin D.sub.3 to persons having a tendency for decreased bone density, postmenopausal women, and periodontal disease patients in a maintenance phase; and even an extended period of administration provides a high degree of safety.