Forty-five women (35–45 year) were randomly assigned to three iron (Fe) absorption sub-studies, which
measured the effects of dietary animal proteins on the absorption of heme Fe. Study 1 was focused on
heme, red blood cell concentrate (RBCC), hemoglobin (Hb), RBCC + beef meat; study 2 on heme,
heme + fish, chicken, and beef; and study 3 on heme and heme + purified animal protein (casein, collagen,
albumin). Study 1: the bioavailability of heme Fe from Hb was similar to heme only (13.0%). RBCC
(25.0%) and RBCC + beef (21.3%) were found to be increased 2- and 1.6-fold, respectively, when compared
with heme alone (p < 0.05). Study 2: the bioavailability from heme alone (10.3%) was reduced (p < 0.05)
when it was blended with fish (7.1%) and chicken (4.9%), however it was unaffected by beef. Study 3:
casein, collagen, and albumin did not affect the bioavailability of Fe. Proteins from animal source foods
and their digestion products did not enhance heme Fe absorption.