“…Although the extrinsic tag technique can be a powerful tool for iron bioavailability research, it is not always considered appropriate for use in human studies. Safety and ethical considerations impose limitations on the use of 55Fe and 59Fe with children and adults of reproductive age (Garni et al, 1980). On the other hand, Bothwell et al (1979), provide substantial evidence to support the case that the radioiron extrinsic tag method is safe and acceptable to use in human subjects.…”