This invention relates to a cysteine protease inhibitor comprising casein
which is a protein derived from milk, a partial peptide of casein, and/or
hydrolysate of casein as an active ingredient. The cysteine protease
inhibitor of the present invention can be used as preventive or
therapeutic drug for osteoporosis, malignant hypercalcemia, breast
cancer, prostate cancer, periodontitis or bacterial and viral infectious
diseases, and food, drink, feed and the like.
