Measurement of iron absorption from compositite meals.

In earlier studies using the recently introduced extrinsic tag technique meals were carefully minced and mixed with the extrinsic tracer to ensure complete isotopic exchange. In the present paper the validity of simpler and more realistic techniques to label and serve composite meals was evaluated. Equal or almost equal absorption figures were found when mixing the label homogenously into a meal, adding it dropwise, or mixing it into the most bulky component of the meal. The necessity of serving the meals in a realistic way was underlined by the finding of higher absorption from a meal in which the components were served separately than from meals mixed before serving. The results of the present study indicate that the validity of using the reference dose as a basis for comparison of absorption data in different groups, was higher when serving the reference dose and the meals on consecutive days than when serving 2 weeks apart. This was true especially in women. The present findings imply that it is both necessary and possible to design simple labeling techniques that allow valid measurements of iron absorption from composite meals. Moreover, when determining the schedule of serving the meals and the reference doses the findings in the present paper must be carefully considered.