Nonheme Iron Absorption in Young Women Is Not Influenced by Purified Sulfated and Unsulfated Glycosaminoglycans

Abstract

Meat is a well-known enhancer of iron absorption, yet the molecular entity mediating the effect remains obscure. Recently published data indicate that highly acidic sulfated glycosaminoglycans (GAG) from fish and chicken muscle are effective stimulants of iron uptake in Caco-2 cells. Two fully randomized stable isotope studies with crossover design were performed in a group of 16 apparently healthy young women to assess the effect of purified sulfated and unsulfated GAG on human iron absorption. Iron absorption was measured on the basis of erythrocyte incorporation of (57)Fe or (58)Fe 14 d after the administration of labeled semisynthetic meals (SSM) based on egg albumin, corn oil, maltodextrin, and water. The meals were consumed with or without added sodium hyaluronate (NaH, 300 mg) or chondroitin sulfate (CS, 360 mg) as representative unsulfated and sulfated GAG, respectively. The level of GAG added was 3 times (NaH) to about 10 times (CS), the amount expected to be present in 150 g beef muscle. Geometric mean iron absorption from SSM containing NaH (21.2%) or CS (19.4%) did not differ from that of SSM without GAG (19.5 and 20.3%, respectively). NaH and CS at those levels do not affect human nonheme iron absorption.

Review: The Potential of the Common Bean (Phaseolus vulgaris) as a Vehicle for Iron Biofortification

“…Different types of glycosaminoglycans (GAG), which are part of the connective tissue between muscle fibers, have also been the subject of investigations. However, although GAGs promoted iron uptake in Caco-2 cells [ 185 , 186 ], a human study failed to show an effect on iron absorption [ 187 ]. Armah and colleagues [ 188 ] have also suggested that phosphatidyl choline contributes to the enhancing effect of meat.…”

Homogenization, lyophilization or acid-extraction of meat products improves iron uptake from cereal–meat product combinations in an in vitro digestion/Caco-2 cell model

“…With respect to the meat factor that enhances non-haem iron absorption, many constituents have been studied: amino acids ( 35 , 36 ) , animal protein ( 37 – 40 ) and carbohydrate fractions ( 17 , 41 ) . From acid extracts of fish, heparin-like glycosaminoglycans increased iron uptake in an in vitro digestion/Caco-2 cell model ( 17 ) ; the active fractions were identified as the low-molecular-weight carbohydrate degradation products of the glycosaminoglycans.…”

“…From acid extracts of fish, heparin-like glycosaminoglycans increased iron uptake in an in vitro digestion/Caco-2 cell model ( 17 ) ; the active fractions were identified as the low-molecular-weight carbohydrate degradation products of the glycosaminoglycans. A human bioavailability study with purified glycosaminoglycans that were not acid-extracted found no improvements in iron bioavailability compared to a semi-synthetic meal with no glycosaminoglycans ( 41 ) . The key to glycosaminoglycans improving iron bioavailability may lie with their acid extraction from a food source ( 42 ) .…”