Trace lipid from whey-mineral complex enhances calcium availability in young ovariectomized rats

The effects of the trace lipids (L1 and L2) extracted from two kinds of whey-mineral complex on bone metabolism were studied in young ovariectomized (OVX) rats. The concentrations of oestradiol in the L1 and L2 oils were 305 and 1313 pg/ml respectively, while the concentrations of progesterone were 34.3 and 36.9 ng/ml respectively. Trace amounts of 1 alpha,25-dihydroxycholecalciferol (1 alpha,25-(OH)2D) were detected: 56 pg/ml in the L1 oil and 132 pg/ml in the L2 oil. The OVX rats were orally given 0.4 ml each test oil twice weekly. Other animals were given with only a vehicle (control) or an oil mixture with similar levels of oestradiol and progesterone to those in L2 oil (PE oil) for comparison. The Ca absorption rate, bone density of the humerus and femoral Ca content in the rats given L2 were significantly higher than those in the control rats (P < 0.05). Serum calcitonin and 1 alpha,25-(OH)2D from rats given L2 were both significantly higher than those from the control rats, while serum progesterone in the L2 group was slightly lower. It is suggested that the bone metabolism of rats given L2 reflected the compound effect of 1,25-(OH)2D and oestradiol in the L2 oil. In contrast, the relatively low level of these hormones might have been associated with the mediocre bone characteristics of the L1 group. It is suggested from these results that the trace level of hormones could be one of the reasons why whey-mineral complex showed good Ca availability.