Background: Repeated phytic acid consumption leads to iron absorption adaptation but, to the best of our knowledge, the impact of repeated tannin consumption has not yet been established. Salivary proline-rich proteins (PRPs) may improve iron absorption by precipitating tannins. Objectives: This study aimed to determine the effect of long-term, dose-response condensed tannin supplementation on iron bioavailability and status and to assess the effect of salivary proteins on iron bioavailability during prolonged condensed tannin consumption. A secondary objective was to assess astringency as a potential marker for adaptation to tannins and iron bioavailability. Methods: Eleven nonanemic women were enrolled in a double-blind 3-dose crossover trial. Three (1.5, 0.25, or 0.03 g) condensed tannin supplements were consumed 3 times/d for 4 wk in random order, with 2-wk washouts in between. Meal challenges were employed before and after supplementation to assess iron bioavailability, iron status, salivary PRP changes, and astringency. Results: Tannin supplementation in any dose did not change iron bioavailability at any dose (P > 0.82) from weeks 0 to 4. Hemoglobin (P = 0.126) and serum ferritin (P = 0.83) were unchanged by tannin dose from weeks 0 to 4. There were significant correlations among tannin supplementation and iron bioavailability, basic proline-rich proteins (bPRPs) (r = 0.366, P = 0.003), and cystatin production (r = 0.27, P = 0.03). Astringency ratings did not change significantly within or between tannin doses (P > 0.126), but there were negative relations among bPRP (r < −0.32, P < 0.21), cystatin production (r < −0.2, P < 0.28), and astringency ratings. Conclusions: Condensed tannin consumption did not affect iron bioavailability or status regardless of the supplementation period in premenopausal nonanemic women. Correlation analyses suggest that bPRPs and cystatins are associated with improved iron bioavailability and that lower ratings of astringency may predict improved iron absorption with repeated tannin consumption.
Background Acute phytic acid intake has been found to decrease iron bioavailability; however, repeated phytic acid consumption leads to iron absorption adaptation. Salivary proline-rich proteins (PRPs) have been shown to inhibit iron chelation to tannins and may mediate similar iron absorption adaptation with phytic acid intake. Objectives The objectives of this study were to determine whether salivary proteins bind to phytic acid in vitro, and to explore a proof of concept in a pilot study that examined the impact of 4-wk, daily phytic acid supplementation on individuals’ iron status, bioavailability, and salivary PRP concentrations. Methods High-performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization–time of flight were used to characterize in vitro salivary protein–phytic acid interactions. Nonanemic women ( n = 7) consumed 350 mg phytic acid supplements 3 times daily for 4 wk, and meal challenges were employed to determine iron bioavailability, iron status, and salivary protein concentrations before and after supplementation periods. Enzyme-linked immunosorbent assay (ELISA) analysis of purified protein fractions and participant saliva identified proteins bound to phytic acid. Results In vitro salivary protein–phytic acid interaction identified cystatin SN, a non–proline rich salivary protein, as the specific bound protein to phytic acid. Iron bioavailability ( P = 0.32), hemoglobin ( P = 0.72), and serum ferritin ( P = 0.08) concentrations were not reduced from week 0 to week 4 after phytic acid supplementation. Basic PRPs and cystatin SN concentrations were positively correlated with iron bioavailability at week 4. Conclusions Overall, results suggest that phytic acid binds to the non-PRP cystatin SN and that salivary protein production may improve iron bioavailability with phytic acid consumption.
BackgroundCorn- and soybean-based fortified blended foods (FBFs) have been the primary food aid product provided by the United States. Sorghum and cowpea have been suggested as alternative FBF commodities because they are drought-tolerant, grown in food aid–receiving areas, and not genetically modified. Extrusion processing has also been suggested to improve the quality of these FBFs.ObjectivesThe aim of this study was to determine the protein quality and iron and vitamin A bioavailability of novel FBFs in broiler chickens.MethodsWhey protein concentrate (WPC)–containing FBFs corn-soy blend 14, sorghum-soy, and sorghum-cowpea (SC); a soy protein isolate (SPI)–containing SC FBF (SC+SPI); 2 reformulated, overprocessed SC FBFs (O-SC+WPC, O-SC+SPI); and a nonextruded WPC-containing SC FBF were developed. Nonextruded corn-soy blend plus (CSB+), a currently used FBF, and a gamebird starter/grower diet were used as comparison diets. In the prepared FBF study, 9 groups of 8-d-old broiler chicks (n = 10) consumed prepared FBFs for 21 d. In the dry study, 8 groups of 4-d-old broiler chicks (n = 24; control: n = 23) consumed dry FBFs for 14 d. Results were analyzed by 1-factor ANOVA with least-significant-difference test.ResultsIn the prepared study, novel formulated FBFs significantly increased caloric and protein efficiency and nonsignificantly increased body weight gain, despite similar food intake compared with CSB+. In the dry study, novel formulated FBFs, except for O-SC+SPI, significantly increased food intake, caloric efficiency, and protein efficiency and nonsignificantly increased body-weight gain compared with CSB+. Novel formulated FBFs nonsignificantly and significantly increased hepatic iron concentrations compared with all FBFs in the prepared and dry studies, respectively.ConclusionNovel formulated FBFs, apart from O-SC+SPI, resulted in improved protein efficiencies and hepatic iron concentrations compared with CSB+, suggesting that they are of higher nutritional quality.
BackgroundCorn and soybean based fortified blended foods (FBFs) have been the primary food aid product provided by the United States. Sorghum and cowpea have been suggested as alternative FBF commodities because they are drought‐tolerant, can be locally grown in areas where food aid is provided, and are not genetically modified.ObjectiveTo determine protein quality and iron bioavailability of newly formulated sorghum, cowpea, soy, and corn‐based FBFs, compared with the current United States Agency for International Development corn and soy blend FBF, CSB+, in broiler chickens, which have been suggested to be a good model for iron bioavailability.MethodsNine groups of one‐day old broiler chicks (n = 10) consumed control chicken diet for one week before being randomized to consume prepared FBFs. The FBFs consisted of corn‐soy blend 14, white sorghum‐soy, white sorghum‐cowpea, white sorghum‐cowpea with soy protein isolate (instead of whey protein concentrate) extruded FBFs, two over‐extruded white sorghum‐cowpea FBFs (one with soy protein isolate), a non‐extruded sorghum‐cowpea FBF, CSB+, or a control chicken diet for 21 days. Results were analyzed by one‐way ANOVA with LSD test using SAS Studio 3.6.ResultsAll newly formulated FBFs resulted in significantly higher protein efficiency ratio and caloric efficiency than CSB+. Unlike CSB+, all newly formulated FBFs resulted in significantly increased hepatic iron levels compared to the control group. The white sorghum‐soy group had significantly increased body weight compared to all other FBFs, except the corn‐soy blend 14 group.ConclusionNewly formulated FBFs' higher protein quality and iron bioavailability compared to CSB+, suggests they are of higher nutritional quality. Further research is needed to identify the best new FBF formulations.Support or Funding InformationSupported by USDA‐MFFAPP.
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