Considerations on the use of radioisotopes in human nutrition research.

Tracer methodology using radioisotopes in human nutrition and metabolism research has been very productive but its use has been the object of unjustified limitations because of modeling decisions without adequate consideration of new data. These limitations have encumbered research studies in the metabolism of micro- and macronutrients particularly where nutritional deficiencies are prevalent. Even though stable isotope methodologies in human research are very useful in specific applications they are expensive and are often fraught with serious pitfalls, when compared to studies for the same purposes using radioisotopes. We have been developing safe radioisotopic methods to study the absorption and metabolism of micronutrients, especially iron and zinc, that can be applied to populations in the developing world. These and other applications of radioisotopes should allow scientists to conduct research diminishing the dependence on stable isotopes and on facilities and laboratories existing only in selected sites in the industrial world, and thus should enhance productive local and collaborative research. All radioisotopic research must be subjected to strict safety criteria, based on scientific evidence of risk, but should not be hampered by exaggerated fears of unfounded risk. Examples on the use of radio and stable isotopes to study iron and zinc absorptions are given including the radiation exposure and risk calculations.