Calcium (Ca++) is found in food in isotopes of different heights, e.g. 42Ca or 44Ca. Isotopes react chemically in the same way, but have different weights. Calcium isotopes are stable and not radioactive.

Ca isotope values in blood and serum are plotted with their corresponding mean values for diet, feces, and calculated mean value for bone. There is no statistical difference in Ca isotope values between the two groups with respect to diet (p = 0.3) or feces (p = 0.6). However, women suffering from DXA-diagnosed osteoporosis showed significantly lower δ44/42Ca (serum) (p = 0.001) and δ44/42Ca(urine) (p = 0.004) values than women without osteoporosis.

The 42Ca/44Ca (δ44/42Ca) ratio can be used to conclude whether bone is built up or broken down. The measurement reflects calcium buildup/loss, which can be converted to grams/day. We will add the algorithm here shortly.

Light Ca isotopes undergo chemical reactions faster than heavy ones and accumulate at the end of the process (in bone in humans). Because light Ca isotopes react faster, predominantly light Ca isotopes (42Ca) are incorporated during bone formation.

When more light Ca isotopes are incorporated in bone, more heavy Ca isotopes (44Ca) remain in blood/urine. This can be measured with our new method. When bone substance is broken down (e.g. osteoporosis), the reverse happens. More light Ca isotopes are released from the bone into the blood/urine. This can also be measured. The graph shows the differences of the Calcium Isotope Marker (CIM) in different materials in healthy and osteoporotic patients.