Jr. Hunt et Zk. Roughead, Adaptation of iron absorption in men consuming diets with high or low ironbioavailability, AM J CLIN N, 71(1), 2000, pp. 94-102
Background: Short-term measurements of iron absorption are substantially in
fluenced by dietary bioavailability of iron, yet bioavailability negligibly
affects serum ferritin in longer, controlled trials.
Objective: Our objective was to test the hypothesis that in men fed diets w
ith high or low iron bioavailability, iron absorption adapts to homeostatic
ally maintain body iron stores.
Design: Heme- and nonheme-iron absorption from whole diets were measured in
31 healthy men at 0 and 10 wk while the men consumed weighed, 2-d repeatin
g diets with either high or low iron bioavailability for 12 wk. The diets w
ith high and low iron bioavailability contained, respectively, 14.4 and 15.
3 mg nonheme Fe/d and 1.8 and 0.1 mg heme Fe/d and had different contents o
f meat, ascorbic acid, whole grains, legumes, and tea.
Results: Adaptation occurred with nonheme- but not with heme-iron absorptio
n. Total iron absorption decreased from 0.96 to 0.69 mg/d (P < 0.05) and in
creased from 0.12 to 0.17 mg/d (P < 0.05) after 10 wk of the high- and low-
bioavailability diets, respectively. This partial adaptation reduced the di
fference in iron bioavailability between the diets from 8- to 4-fold. Serum
ferritin was insensitive to diet but fecal ferritin was substantially lowe
r with the low- than the high-bioavailability diet. Erythrocyte incorporati
on of absorbed iron was inversely associated with serum ferritin.
Conclusions: Iron-replete men partially adapted to dietary iron bioavailabi
lity and iron absorption from a high-bioavailability diet was reduced to ap
proximate to 0.7 mg Fe/d. Short-term measurements of absorption overestimat
e differences in iron bioavailability between diets.