Effect of thickening agents, based an soluble dietary fiber, on the availability of calcium, iron, and zinc from infant formulas

Although it is accepted that dietary fiber probably is not needed in the di ets of infants younger than 1 y, babies suffering from regurgitation are of ten fed with infant formulas thickened with considerable amounts of fiber. The effect of increasing amounts of alginic acid, locust-bean gum, and guar gum was studied from casein and whey-based infant formulas. A dialysis in vitro method with preliminary intraluminal digestion, adapted to the condit ions of infants younger than 6 mo, was used. Human milk was used as the ref erence standard. Elemental contents of samples and dialysates were determin ed by atomic absorption spectrometry. Soluble dietary fiber inhibited miner al availability mon in casein than in whey-based formulas. Mineral availabi lities from casein- and whey-based formulas supplemented with 0.42 g of loc ust-bean gum/100 mL, were 9.4%.(0.7) and 10.4% (0.6) for calcium (P < 0.05) , 0.32% (0.08) and 1.45% (0.17) for iron (P < 0.05), and 3.2% (0.2) and 5.6 % (0.5) for zinc (P < 0.05), respectively. Calcium availability from the wh ey formula decreased in the presence of each fiber source, especially guar gum and alginic acid. Supplementing 2 g of alginic acid-based agents per 10 0 mt depressed calcium availability from 13.3% (1.2) to 5.3% (0.3; P < 0.05 ). With respect to iron and zinc, availabilities increased from 1.28% (0.28 ) to 6.05% (0.96; P < 0.05) and from 6.7% (0.6) to 10.2% (1.0), respectivel y, with the addition of 2 g of alginic acid (P < 0.05). Both gums lowered i ron and zinc availabilities, and guar gum affected iron availability more s everely than locust-bean gum did. iron availabilities were 1.45% (0.17) fro m formula thickened with locust-bean gum (0.42 g/100 mt) and 0.92% (0.15) f rom formula thickened with guar gum (P < 0.05). Adding thickening agents ba sed on soluble dietary fiber to traditional infant formulas probably affect s calcium, iron, and zinc availability in various ways. (C) Elsevier Scienc e Inc. 2001.