The characteristics of vegetarian diets suggest that these diets would have lower dietary iron bioavailability than nonvegetarian diets, but there is no evidence of iron deficiency in vegetarians.
We evaluated the responsiveness of serum and fecal ferritin to differences in iron absorption from controlled lactoovovegetarian and nonvegetarian diets.
Twenty-one women aged 20-42 y with serum ferritin concentrations from 6 to 149 microg/L consumed lactoovovegetarian and nonvegetarian weighed diets for 8 wk each (crossover design). The diets differed substantially in meat and phytic acid contents. Nonheme-iron absorption was measured from the whole diets after 4 wk by using extrinsic 59Fe and whole-body counting. Ferritin in extracts of fecal composites and in serum was measured by enzyme-linked immunosorbent assay the last 2 wk of each diet.
Nonheme-iron absorption was less from the lactoovovegetarian diet than from the nonvegetarian diet (1.1% compared with 3.8%; P < 0.01; n = 10). Diet did not affect hemoglobin, transferrin saturation, erythrocyte protoporphyrin, or serum ferritin. Substantially less fecal ferritin was excreted with the lactoovovegetarian diet than with the nonvegetarian diet (1.1 compared with 6.0 microg/d, respectively; P < 0.01; n = 21).
This research indicates 1) 70% lower nonheme-iron absorption from a lactoovovegetarian diet than from a nonvegetarian diet; 2) an associated decrease in fecal ferritin excretion, suggesting partial physiologic adaptation to increase the efficiency of iron absorption; and 3) an insensitivity of blood iron indexes, including serum ferritin, to substantial differences in dietary iron absorption for 8 wk.