Bioavailability of dietary minerals to humans: the stable isotope approach

A number of minerals contained in foods are essential nutrients for humans, animals, and/or plants. While most vitamins are very well absorbed, most essential minerals are not. Usual absorption of minerals ranges from less than 1% to over 90%. The bioavailability of dietary minerals must be considered when determining whether the diet contains enough, too little, or too much. By using stable isotope tracers as labels, the metabolic fate of minerals in a specific day's diet, a specific meal, or a food can be distinguished from minerals from other sources and followed. A number of mass spectrometric methods have been used to measure stable isotopes. Magnetic sector, thermal ionization mass spectrometry (TIMS) is used routinely in our laboratory to study bioavailability of Zn, Cu, and Fe. Other mass spectrometric methods that are less precise, but useful for many applications requiring isotopic determinations include quadrupole TIMS, inductively coupled plasma mass spectrometry (ICP/MS), and fast atom bombardment mass spectrometry (FAB/MS). One of the major advantages of stable isotope studies is that multiple isotopes of the same mineral can be used simultaneously and multiple minerals can be studied simultaneously. The use of stable isotopes for studies of bioavailability of minerals in foods has gained widespread interest in recent years. The approach is expected to be applied to an increasing number of food science and nutrition problems in the future.