Intestinal solubility and absorption of ferrous iron in growing rats are affected by different dietary pectins

The effects of pectin structure on iron solubility were examined in vivo and in vitro using pectins differing in degree of esterification (DE) and molecular weight (MW). The pectins prepared differed (in DE and MW, respectively) as follows: P-A (73%, 860,000), P-B (75%, 89,000), P-C (22%, 1,260,000) and P-D (24%, 114,000). Weanling rats were trained to consume a basal diet containing ferrous sulfate as the iron source within 2 h. Food-deprived rats were presented the basal diet or the same diet containing one of the pectins at 80 g/kg diet. One hour after the meal, soluble, insoluble and tissue iron in intestinal segments and serum iron concentration in portal blood were determined and amounts of absorbed iron were calculated. Portal blood iron and calculated absorbed iron were highly correlated (r = 0.97). None of the pectins reduced iron solubility or absorption below that in rats fed the basal diet. Addition of P-B increased the amount of iron absorbed and postprandial serum iron concentration in portal blood. Solubility of ferrous sulfate in vitro was higher in solutions containing pectins than in a cornstarch solution (P < 0.05) and was also higher in diets containing pectin than in the basal diet (P < 0.05). The pectin with the high DE and low MW (P-B) improved iron solubility and absorption of solubilized iron.