Relationship of components in wheat bran and spinach to iron bioavailability in the anemic rat

Components found in wheat bran and spinach were evaluated as to their affect on the bioavailability of ferrous iron (i.e., FeSO4) by using the criteria of hemoglobin regeneration in anemic rats. The relative biological value (RBV) of iron in wheat bran and spinach (FeSO4 = 100%) were determined to be 124 and 53%, respectively. Control diets with graded levels of FeSO4 did not contain dietary fiber (i.e., cellulose). Adding cellulose (1.74%) or phytic acid (0.66%) at levels contained in the wheat bran diet, significantly increased (P less than 0.05) the RBV f the ferrous iron to 126 and 124%, respectively. The addition of 2.10% oxalic acid, the amount in the spinach diet, caused the highest increase in RBV to 164%. Combining these dietary components, plus lignin (0.67%) and pectin (0.63%), in various combinations, resulted in RBVs equivalent or significantly higher than 100%. The bioavailability of iron in plant foods appears to be dependent on how this nutrient is presented to the mucosa. Cellulose, phytate or oxalate added to a purified diet containing ferrous iron significantly enhanced the bioavailability of this element. Relative biological values for iron were also calculated based on food intake and growth rate. The latter parameters are believed to have greater utility in determining RBV when food intake and/or growth rate may vary among animals consuming different sources of test iron.