Dietary proteins that influence nonheme iron bioavailability, iron status, and plasma total antioxidant status

The objective of the first study was to isolate and characterize beef proteins that enhance nonheme iron bioavailability. Beef sirloin was cooked, lyophilized and reconstituted prior to in vitro digestion. The digest supernatant was sequentially ultrafiltered using 10K and 1K molecular weight cut-off membranes. Caco-2 cell 59Fe uptake was 45.2% and 56.5% higher (p < 0.05) with the 1-kDa retentate (1KR) as compared to the 10-kDa retentate and 1-kDa filtrate, respectively, and 2- to 5-fold greater than the blank (p < 0.05) IMAC of the (1KR) yielded a series of peaks (P1--P4). P1--P4 all increased (p < 0.001) iron solubility at pH 6 as compared to the blank. Iron uptake with P2 and P4 was greater than the blank (p < 0.05) SDS-PAGE illustrated that P1--P4 each contained peptides from 1- to 5-kDa. MALDI-TOF analysis confirmed these findings. Amino acid analysis revealed that histidine concentration increased progressively in (P1--P4). Results suggest that enhancement of nonheme iron absorption by beef may be due to peptides produced during gastrointestinal digestion and that histidine content may be important.;The objective of the second study was to determine the effect of soy protein isolate (SPI) intake on iron indices and plasma total antioxidant status (TAS), and determine the influence of other factors on TAS in perimenopausal women (N = 69). Subjects were randomly assigned to treatment: isoflavone-rich soy (SPI+), isoflavone-poor soy (SPI-), or whey protein (control) for 24 weeks. TAS, serum ferritin (SF), serum iron (SI), transferrin saturation (TS), and hemoglobin were measured at baseline, week 12, and week 24. Treatment had no effect on SIT, SI, and TS. Time effected SF (P ≤ 0.0001) and TAS (P ≤ 0.0001). At week 12, TAS was lower (P = 0.035) in controls than SPI+, whereas no differences were found between SPI+ and SPI- at week 12 or 24. Multiple regression analysis revealed that at week 12, baseline TAS, alcohol intake, soy intake (P = 0.016), plasma Lp(a), and dietary iron contributed to the variability (48%; P ≤ 0.0001) in TAS. At week 24, 46% of the variability in TAS was contributed by baseline TAS, dietary meat, fish, and poultry and zinc, SF and serum estrone. SPI consumption had no significant effect on iron status, but our results suggest that soy intake and decreased iron stores may protect from oxidative stress in perimenopausal women.