Effect of Sodium Nitrite on the Bioavailability of Meat Iron for the Anemic Rat

Abstract

During the curing of meat, added nitrite is converted to nitric oxide which covalently combines with the porphyrin bound iron yielding the characteristic pink color of cured meat upon heating. Anemic rats were fed diets containing bologna prepared with different levels of nitrite to determine the effects of nitrite curing on the bioavailability of meat iron. In experiment 1, the efficiency of converting meat iron to hemoglobin iron was decreased from 58 to 39% and water extractable iron decreased from 8.7 to 2.6 mg/kg bologna as sodium nitrite added to the bologna emulsion was increased from 0 to 50 ppm. The efficiency of converting meat iron to hemoglobin iron tended to increase at sodium nitrite levels above 50 ppm. In experiment 2, the apparent absorption values were not decreased in response to adding sodium nitrite to the bologna emulsion but the efficiency of the conversion of absorbed meat iron to hemoglobin iron was clearly depressed. In experiment 3, addition of 12 mg nitrite per kg casein or bologna diet, an amount equivalent to the residual nitrite present in the high nitrite bologna, caused increases in the hematinic response. This is discussed in terms of nitrosylmethemoglobinemia and relative tissue hypoxia. The results of experiment 1 were confirmed in experiment 4. Thus, using a very sensitive animal model it has been possible to show that even very low levels of nitrite used in curing meat can have measurable physiological effects on the metabolism of meat iron. Furthermore, very low levels of dietary nitrite from any source may be physiologically significant.