Short communication: Proteins in heat-processed skim milk powder have no positive effects on bone loss of ovariectomized rats

Abstract

Milk has positive effects on bone growth. However, the effect of skim milk powder (SMP) on bone properties has not been reported. This study investigated the effect of SMP on bone loss in ovariectomized (OVX) rats. Forty female Sprague-Dawley rats were ovariectomized and another 10 rats received a sham operation. The OVX rats were randomly separated into 4 groups: OVX control, OVX SMP1 (SMP at 0.04 g/d), OVX SMP2 (SMP at 0.20 g/d), and OVX SMP3 (SMP at 0.40 g/d). Skim milk powder was supplied in the rat diet for 12 wk, and the rats were gavaged once per day. The effects of SMP on calcium content and bone mineral density of femur were determined by atomic absorption spectrophotometry and dual-energy x-ray absorptiometry, respectively. Compared with the control, SMP at all dose levels tested had no particular effect on weight:length, calcium content, or bone mineral density of femurs. It was demonstrated that SMP (0.04 to 0.40 g/d) had no positive effect on bone loss in OVX rats, probably because the heat treatment used during SMP processing caused a loss of biological activity in the protein.

Invited review: Dairy intake and bone health: A viewpoint from the state of the art

“…Consistently, skim milk powder had no effect on bone loss in ovariectomized rats probably due to a loss of biological protein activity consequent to processing heat treatment (Du et al, 2011a).…”

Purification and Identification of Lactoferrin from Bovine Milk

“…Lactoferrin was found not only in milk, but also in other external secretions, such as saliva, tears, semen, and mucosal secretions [1] , and as an important constituent of the neutrophilic granules of leucocytes [2] . These varied locations of lactoferrin are a key feature of its biology [3] , such as anti-bacteria, anti-tumor, anti-inflammation and skeletal growth-promotion activity and so on [4,5] . With the development of economy, the living standard has been improved, which enhances the requirement of nutritional and healthy food products.…”