The bone-strengthening activity of milk basic protein is not dependent on lactoferrin

Abstract

Milk contains components important for bone health. We have previously reported that milk basic protein (MBP) enhances bone formation and suppresses bone resorption. Lactoferrin (LF), a basic iron-binding protein in milk, also improves bone metabolism. However, the contribution of LF to the bone-strengthening activity of MBP is unclear. Here we compared the effects of MBP and LF on bone cells in vitro and bone strength in vivo. MBP showed greater stimulatory effects than did LF on the proliferation and differentiation of osteoblasts. MBP was also more effective than LF in terms of inhibiting bone resorption by osteoclasts. The force required to break bones in ovariectomised rats was significantly greater in rats fed 0.1% MBP than in rats fed 0.1% LF. These results suggest that the effects of MBP on bone metabolism are not solely due to LF; rather, multiple components in MBP may act together to improve bone metabolism.