Stable isotopes are very useful tools which are used extensively in scientific research. Within the field of nutritional studies stable isotopes are used for studying the flow of nutrients through the human body. Since they are safe and non-radioactive they can even be used in infants and pregnant women.
Compounds containing stable isotopes can be identified and measured using the molecular weight of the compound. This is because it will differ from that of the original compound. Using an instrument called a mass spectrometer, researchers can use this weight difference to trace the stable isotopes as they travel through the body and appear in blood, urine, breath, and stool samples.
The first paper published that described the use of a stable isotope tracer in a human metabolic study was in 1963. Today, there are four commonly studied isotopes used in nutrition studies, which include calcium, iron, magnesium and zinc.
Calcium Isotopes are used at length in clinical research studies. Calcium has six stable isotopes, which include 40Ca, 42Ca, 43Ca, 44Ca, 46Ca and 48Ca. They are used to measure calcium absorption mainly in women and children. In adults, calcium deficiency is strongly related to increasing severity of osteoporosis. In children, calcium deficiency is primarily related to the development of rickets. (S.A. Abrams and W.W. Wong, Stable Isotopes in Human Nutrition, 2003).
There are four stable Iron Isotopes: 54Fe, 56Fe, 57Fe and 58Fe. The two most commonly used isotopes in nutritional studies are 57Fe and 58Fe. One study, conducted by the University of Iowa and the University of Texas (Samuel J. Fomon et al., January 2003) involved the use of 58Fe to study iron-loss by human adolescents. The investigators were able to estimate inevitable iron loss by adolescents because total body iron of the adolescents had been enriched with the stable isotope, 58Fe, as the result of earlier studies of iron absorption. At the conclusion of this study, they were able to estimate the requirement for absorbed iron.