Milk has more beneficial effects on bone health than other food sources. Recent in vitro and in vivo studies have shown that milk whey protein, especially its basic protein fraction (milk basic protein, MBP), contains several components capable of promoting bone formation and inhibiting bone resorption. The object of this study was to examine the effect of MBP on the bone metabolism of healthy menopausal women. Thirty-two healthy menopausal women were randomly assigned to treatment with either placebo or MBP (40 mg per day) for 6 months. The bone mineral density (BMD) of the lumbar vertebrae L2-L4 of each subject was measured by dual-energy X-ray absorptiometry (DXA) at 0 and 6 months of treatment. Serum and urine indices of bone metabolism were measured at 0, 3 and 6 months. Twenty-seven subjects who completed the study in accordance with the protocol were included in the analysis. The mean rate of gain of lumbar BMD in the MBP group (1.21%) was significantly higher than in the placebo group (-0.66%, P=0.046). When compared with the placebo group, urinary cross-linked N-telopeptides of type-I collagen (NTx) were significantly decreased in the MBP group at 6 months, but no significant difference in serum osteocalcin was observed between the two groups. The urinary NTx excretion was found to be related to serum osteocalcin in the MBP group at 3 and 6 months, indicating that MBP maintained the balance of bone remodeling. These results suggested that MBP supplementation was effective in preventing bone loss in menopausal women and that this improvement in BMD may be primarily mediated through the inhibition of bone resorption while maintaining the balance of bone remodeling by MBP supplementation.