Jfr. Barrett et al., COMPARISON OF STABLE ISOTOPES AND RADIOISOTOPES IN THE MEASUREMENT OFIRON-ABSORPTION IN HEALTHY WOMEN, Clinical science, 87(1), 1994, pp. 91-95
1. Stable isotope methods are being used to investigate the absorption
of dietary iron. In order to be certain that this new methodology is
accurate, we have compared results obtained using stable isotopes and
inductively coupled plasma mass spectrometry with those determined usi
ng a radioisotope and whole body counting. 2. The stable isotope Fe-54
(2.8mg) was given to 10 healthy non-pregnant women. Six women receive
d the isotope in aqueous form, and four took it with a meat meal. The
Fe-54 served as a carrier for 10ng of the radioisotope Fe-59. An ampou
le (200 mu g) of the isotope Fe-57 or Fe-58 was then given intravenous
ly, and in serum samples taken over the next 10 h the ratios of the st
able iron isotopes were measured by inductively coupled plasma mass sp
ectrometry and the oral iron absorption was calculated. This was then
compared with the results obtained by using a whole body counter to me
asure (on day 0 and day 14) the gamma-activity emitted by the radioiso
tope. 3. The mean iron absorption measured by both methods ranged from
8% to 45%. Measurement of the post-absorptive serum enrichment of the
stable isotopes provided estimates of absorption from both aqueous an
d food iron which were similar to that yielded by whole body counting,
the mean difference being -1.5% (95% confidence interval -5.2 to 2.1%
). Absorption estimated by stable isotopes exhibited the same inverse
relationship with the serum ferritin level (body iron stores) to that
known to exist with whole body counting. Similar estimates of food iro
n absorption were obtained irrespective of the type of isotope used as
an extrinsic label, implying that stable isotopes are as valid as rad
ioisotopes in reflecting intrinsic food iron absorption. 4. This study
validates the use of stable isotopes and post-absorption curves as a
new and accurate technique in the measurement of iron absorption.