Relative bioavailability of zinc from selected cereals and legumes using rat growth

The relative bioavailability of zinc (RBAZ) in corn, rice, wheat and legumes was determined by the ratio of net weight gains a 6 ppm of added zinc, a measure derived from sigmoidal curves for weight gain estimated by a non-linear, least-squares curve fitting computer program. Each food was prepared as for human consumption, incorporated into a semi-purified diet to provide varying levels of zinc and fed to weanling rats. Among cereals, whole corn and brown rice had low RBAZ (0.58 or less), while whole wheat flour and unleavened whole wheat bread had medium values (0.63-0.74). Refined cereal grains, such as white flour, leavened and unleavened white bread and white rice, had high RBAZ (0.89-1.08) as did leavened whole wheat bread (1.04). Of the legumes, lima beans had a high RBAZ (0.84) while white beans had a medium value (0.74). Phytic acid content of the foods, but not neutral-detergent fiber content, appeared to be inversely related to RBAZ, more so among the cereals than with the legumes.