Manganese retention in man: a method for estimating manganese absorption in man.

Whole-body retention of 54Mn was studied in man by measurements in a sensitive whole-body counter after intake of an extrinsically labeled infant formula. Reproducible retention figures at day 10 were observed after repeated administrations to six subjects; 2.3 +/- 1.1, 3.3 +/- 3.1, and 2.4 +/- 1.4% (means +/- SD) for three separate occasions. Interindividual variation of manganese retention after intake of the same labeled diet was, however, shown to be substantial. Retention at day 10 was 2.9 +/- 1.8% (means +/- SD) and varied from 0.6 to 9.2% when measured in 14 healthy subjects. Large interindividual variations in rate of excretion were observed. The retention measurements for days 10-30, however, could be closely fitted to a single exponential function for each individual. The results regarding intraindividual and interindividual variation in Mn retention indicate that factors influencing Mn absorption can be identified only by repeated administrations using each subject as his/her own control.