Total body bone mineral content (BMC) and its BMCI

Since we used DEXA to determine the whole-body bone mineral content (not the total weight of the bones) of each person examined (709 women and 297 men), we were able to check whether there was a correlation with body size for this parameter and whether the correlation was still detectable after indexing.

Figure 1 shows a clear, highly significant correlation (p<<0.001) between body size and total body mineral content (TBMC). It is noticeable that the trend lines for women and men are almost the same. However, as women are on average smaller than men, they had a lower total body mineral content of 2.8 ± 0.4 kg, while men had a lower total body mineral content of 3.3 ± 0.4 kg (mean value ± standard deviation). The calcium content in women and men increases by around 3 % per cm of body height.

If the index for the total body mineral content (TBMC / height ²) is calculated, identical values are found for women and men for the total body mineral mass index of 1.0 ± 0.1 kg/m²! Rather surprisingly, however, a significant (p<0.05), negative correlation was found between the total body mineral mass index and height in men and women.

However, if you look at the slope of the regression line, it becomes clear that the index only decreases by 3 per thousand for men and 1 per thousand for women per cm of height – i.e. it is hardly significant. The reason for this phenomenon is that an increase in height mainly affects the extremities and the area around the waist, while the shoulder and pelvic girdle as well as the head, i.e. the regions with the highest bone mass per cm length, are probably less affected.

We pointed out the important connection between muscle mass and bone density in the chapter “Sport, exercise and osteoporosis”. We found a much greater increase in bone density with increasing muscle mass in pre-menopausal women than in men. This may be due to the positive effect of oestrogen on the bones.