Iron bioavailability from diets containing high-fiber breakfast cereals and crackers

Hemoglobin repletion experiments were conducted with young chicks to assess the bioavailability of iron (Fe) in 13 high fiber breakfast cereals and crackers, and the effect of fiber on supplemental Fe bioavailability. Intrinsic Fe bioavailability was determined by adding these test foods to a casein-dextrose basal diet to provide 10 mg Fe/kg diet. Test foods contained 8.9-32.5% total dietary fiber (TDF), 11.6-37.4% neutral detergent residue (NDR), 3.9-12.6% acid detergent fiber (ADF), and 1.9-8.7% acid detergent lignin (ADL). Iron bioavailability, determined by the standard curve method, ranged from -24.0 to 125.1% (% bioavailability relative to ferrous sulfate). Bioavailability of Fe in the cereals and crackers was not related to analyzed fiber values, however, Fe from wheat-based products was more available than that from oat-based products. In another experiment, wheat bran, corn bran, and oat bran (providing 1.5-4.0% TDF to the diet), were added to diets containing three levels of ferrous sulfate in a 7 x 3 factorial treatment design. Supplemental Fe bioavailability, determined by the slope-ratio method, was not affected by either level of wheat bran, corn bran, or oat bran. However, at the upper level of oat bran, total Fe availability was decreased. These experiments demonstrate that high-fiber breakfast cereals and crackers display a wide range of intrinsic Fe bioavailability but the main fiber-containing components have no effect on supplemental Fe bioavailability.